1.
Humidity
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Humidity is the amount of water vapor present in the air. Water vapor is the state of water and is invisible. Humidity indicates the likelihood of precipitation, dew, or fog, higher humidity reduces the effectiveness of sweating in cooling the body by reducing the rate of evaporation of moisture from the skin. This effect is calculated in an index table or humidex. The amount of vapor that is needed to achieve saturation increases as the temperature increases. As the temperature of a parcel of water becomes lower it will not reach the point of saturation without adding or losing water mass. The differences in the amount of vapor in a parcel of air can be quite large. For example, a parcel of air that is near saturation may contain 28 grams of water per cubic meter of air at 30 °C, there are three main measurements of humidity, absolute, relative and specific. Absolute humidity is the content of air expressed in gram per cubic meter. Relative humidity, expressed as a percent, measures the current absolute humidity relative to the maximum for that temperature, specific humidity is the ratio of the mass of water vapor to the total mass of the moist air parcel. Absolute humidity is the mass of water vapor present in a given volume of air. It does not take temperature into consideration, absolute humidity in the atmosphere ranges from near zero to roughly 30 grams per cubic meter when the air is saturated at 30 °C. Absolute humidity is the mass of the vapor, divided by the volume of the air and water vapor mixture. The absolute humidity changes as air temperature or pressure changes and this makes it unsuitable for chemical engineering calculations, e. g. for clothes dryers, where temperature can vary considerably. Mass of water per unit volume as in the equation above is defined as volumetric humidity. Because of the confusion, British Standard BS1339 suggests avoiding the term absolute humidity. Units should always be carefully checked, many humidity charts are given in g/kg or kg/kg, but any mass units may be used. The field concerned with the study of physical and thermodynamic properties of mixtures is named psychrometrics
2.
Relative humidity
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Relative humidity is the ratio of the partial pressure of water vapor to the equilibrium vapor pressure of water at a given temperature. Relative humidity depends on temperature and the pressure of the system of interest and it requires less water vapor to attain high relative humidity at low temperatures, more water vapour is required to attain high relative humidity in warm or hot air. Humans are sensitive to high humidity because the body uses evaporative cooling, enabled by perspiration. Perspiration evaporates from the more slowly under humid conditions than under arid. For example, if the air temperature is 24 °C and the humidity is zero percent. If the relative humidity is 100 percent at the air temperature. In other words, if the air is 24 °C and contains saturated water vapor, then the human body cools itself at the rate as it would if it were 27 °C. The heat index and the humidex are indices that reflect the effect of temperature. In cold climates, the temperature causes lower capacity for water vapour to flow about. Dry cracked skin can result from dry air, low humidity causes tissue lining nasal passages to dry, crack and become more susceptible to penetration of Rhinovirus cold viruses. Low humidity is a cause of nosebleeds. The use of a humidifier in homes, especially bedrooms, can help with these symptoms, indoor relative humidities should be kept above 30% to reduce the likelihood of the occupants nasal passages drying out. Humans can be comfortable within a range of humidities depending on the temperature—from thirty to seventy percent—but ideally between 50% and 60%. Very low humidity can create discomfort, respiratory problems, and aggravate allergies in some individuals, in the winter, it is advisable to maintain relative humidity at 30 percent or above. Extremely low relative humidities may also cause eye irritation, wooden furniture can shrink, causing the paint that covers these surfaces to fracture. When the temperature is low and the humidity is high. When relative humidity approaches 100 percent, condensation can occur on surfaces, leading to problems with mold, corrosion, decay, condensation can pose a safety risk as it can promote the growth of mold and wood rot as well as possibly freezing emergency exits shut. The basic principles for buildings, above, also apply to vehicles, in addition, there may be safety considerations
3.
Dew point
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Dew point is the temperature to which air must be cooled to become saturated with water vapor. When further cooled, the water vapor will condense to form liquid dew. Dew point is called frost point when the temperature is below freezing. The measurement of dew point is related to humidity, a higher dew point means there will be more moisture in the air. Given that all the factors influencing humidity remain constant, at ground level the relative humidity rises as the temperature falls. This is because water vapor condenses as the temperature falls. Dew point temperature is never greater than the air temperature because relative humidity cannot exceed 100%. In technical terms, the dew point is the temperature at which the vapor in a sample of air at constant barometric pressure condenses into liquid water at the same rate at which it evaporates. At temperatures below the dew point, the rate of condensation will be greater than that of evaporation, the condensed water is called dew when it forms on a solid surface. The condensed water is called either fog or a cloud, depending on its altitude, a high relative humidity implies that the dew point is closer to the current air temperature. Relative humidity of 100% indicates the dew point is equal to the current temperature, when the moisture content remains constant and temperature increases, relative humidity decreases. General aviation pilots use dew point data to calculate the likelihood of carburetor icing and fog, at a given temperature but independent of barometric pressure, the dew point is a consequence of the absolute humidity, the mass of water per unit volume of air. If both the temperature and pressure rise, however, the dew point will increase and the humidity will decrease accordingly. Reducing the absolute humidity without changing other variables will bring the dew point back down to its initial value, in the same way, increasing the absolute humidity after a temperature drop brings the dew point back down to its initial level. If the temperature rises in conditions of constant pressure, then the dew point will remain constant but the relative humidity will drop. For this reason, a constant relative humidity with different temperatures implies that when it is hotter, a higher fraction of the air is present as water vapor compared to when it is cooler. At a given barometric pressure but independent of temperature, the dew point indicates the fraction of water vapor in the air, or, put differently. If the pressure rises without changing this mole fraction, the dew point will rise accordingly, reducing the mole fraction, i. e. making the air less humid, would bring the dew point back down to its initial value
4.
Dew point depression
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The dew point depression is the difference between the temperature and dew point temperature at a certain height in the atmosphere. For a constant temperature, the smaller the difference, the more there is. In the lower troposphere, more moisture results in lower cloud bases, LCL height is an important factor modulating severe thunderstorms. LCL height also factors in downburst and microburst activity, conversely, instability is increased when there is a mid-level dry layer known as a dry punch, which is favorable for convection if the lower layer is buoyant. As it measures moisture content in the atmosphere, the dew point depression is also an important indicator in agricultural and forest meteorology, particularly in predicting wildfires
5.
Psychrometrics
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Psychrometrics or psychrometry or hygrometry are terms used to describe the field of engineering concerned with the determination of physical and thermodynamic properties of gas-vapor mixtures. The term derives from the Greek psuchron meaning cold and metron meaning means of measurement, in human terms, our thermal comfort is in large part a consequence of not just the temperature of the surrounding air, but the extent to which that air is saturated with water vapor. Many substances are hygroscopic, meaning they attract water, usually in proportion to the humidity or above a critical relative humidity. Such substances include cotton, paper, cellulose, other products, sugar, calcium oxide and many chemicals. Industries that use these materials are concerned with relative humidity control in production, in many industrial applications it is important to avoid condensation that would ruin product or cause corrosion. Molds and fungi can be controlled by keeping humidity low. Wood destroying fungi generally do not grow at relative humidities below 75%, the dry-bulb temperature is the temperature indicated by a thermometer exposed to the air in a place sheltered from direct solar radiation. The term dry-bulb is customarily added to temperature to distinguish it from wet-bulb, in meteorology and psychrometrics the word temperature by itself without a prefix usually means dry-bulb temperature. Technically, the temperature registered by the thermometer of a psychrometer. The name implies that the bulb or element is in fact dry. WMO provides a 23-page chapter on the measurement of temperature, the thermodynamic wet-bulb temperature is a thermodynamic property of a mixture of air and water vapor. The value indicated by a wet-bulb thermometer often provides an approximation of the thermodynamic wet-bulb temperature. The accuracy of a simple wet-bulb thermometer depends on how fast air passes over the bulb, speeds up to 5,000 ft/min are best but it may be dangerous to move a thermometer at that speed. Errors up to 15% can occur if the air movement is too slow or if there is too much radiant heat present, a psychrometer is a device that includes both a dry-bulb and a wet-bulb thermometer. A sling psychrometer requires manual operation to create the airflow over the bulbs, knowing both the dry-bulb temperature and wet-bulb temperature, one can determine the relative humidity from the psychrometric chart appropriate to the air pressure. The ratio of the pressure of moisture in the sample to the saturation pressure at the dry bulb temperature of the sample. The saturation temperature of the present in the sample of air. Usually the level at which water vapor changes into liquid marks the base of the cloud in the atmosphere hence called condensation level, so the temperature value that allows this process to take place is called the dew point temperature
6.
Atmosphere of Earth
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The atmosphere of Earth is the layer of gases, commonly known as air, that surrounds the planet Earth and is retained by Earths gravity. The atmosphere of Earth protects life on Earth by absorbing solar radiation, warming the surface through heat retention. By volume, dry air contains 78. 09% nitrogen,20. 95% oxygen,0. 93% argon,0. 04% carbon dioxide, and small amounts of other gases. Air also contains an amount of water vapor, on average around 1% at sea level. The atmosphere has a mass of about 5. 15×1018 kg, the atmosphere becomes thinner and thinner with increasing altitude, with no definite boundary between the atmosphere and outer space. The Kármán line, at 100 km, or 1. 57% of Earths radius, is used as the border between the atmosphere and outer space. Atmospheric effects become noticeable during atmospheric reentry of spacecraft at an altitude of around 120 km, several layers can be distinguished in the atmosphere, based on characteristics such as temperature and composition. The study of Earths atmosphere and its processes is called atmospheric science, early pioneers in the field include Léon Teisserenc de Bort and Richard Assmann. The three major constituents of air, and therefore of Earths atmosphere, are nitrogen, oxygen, water vapor accounts for roughly 0. 25% of the atmosphere by mass. The remaining gases are often referred to as gases, among which are the greenhouse gases, principally carbon dioxide, methane, nitrous oxide. Filtered air includes trace amounts of other chemical compounds. Various industrial pollutants also may be present as gases or aerosols, such as chlorine, fluorine compounds, sulfur compounds such as hydrogen sulfide and sulfur dioxide may be derived from natural sources or from industrial air pollution. In general, air pressure and density decrease with altitude in the atmosphere, however, temperature has a more complicated profile with altitude, and may remain relatively constant or even increase with altitude in some regions. In this way, Earths atmosphere can be divided into five main layers, excluding the exosphere, Earth has four primary layers, which are the troposphere, stratosphere, mesosphere, and thermosphere. It extends from the exobase, which is located at the top of the thermosphere at an altitude of about 700 km above sea level, to about 10,000 km where it merges into the solar wind. This layer is composed of extremely low densities of hydrogen, helium and several heavier molecules including nitrogen, oxygen. The atoms and molecules are so far apart that they can travel hundreds of kilometers without colliding with one another, thus, the exosphere no longer behaves like a gas, and the particles constantly escape into space. These free-moving particles follow ballistic trajectories and may migrate in and out of the magnetosphere or the solar wind, the exosphere is located too far above Earth for any meteorological phenomena to be possible
7.
Concentration
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In chemistry, concentration is the abundance of a constituent divided by the total volume of a mixture. Several types of mathematical description can be distinguished, mass concentration, molar concentration, number concentration, the term concentration can be applied to any kind of chemical mixture, but most frequently it refers to solutes and solvents in solutions. The molar concentration has variants such as concentration and osmotic concentration. To concentrate a solution, one must add more solute, or reduce the amount of solvent, by contrast, to dilute a solution, one must add more solvent, or reduce the amount of solute. Unless two substances are fully miscible there exists a concentration at which no further solute will dissolve in a solution, at this point, the solution is said to be saturated. If additional solute is added to a solution, it will not dissolve, except in certain circumstances. Instead, phase separation will occur, leading to coexisting phases, the point of saturation depends on many variables such as ambient temperature and the precise chemical nature of the solvent and solute. Concentrations are often called levels, reflecting the mental schema of levels on the axis of a graph. There are four quantities that describe concentration, The mass concentration ρ i is defined as the mass of a constituent m i divided by the volume of the mixture V, ρ i = m i V. The molar concentration c i is defined as the amount of a constituent n i divided by the volume of the mixture V, c i = n i V, however, more commonly the unit mol/L is used. The number concentration C i is defined as the number of entities of a constituent N i in a divided by the volume of the mixture V, C i = N i V. The volume concentration ϕ i is defined as the volume of a constituent V i divided by the volume of the mixture V, ϕ i = V i V. Being dimensionless, it is expressed as a number, e. g.0.18 or 18%, several other quantities can be used to describe the composition of a mixture. Note that these should not be called concentrations, normality is defined as the molar concentration c i divided by an equivalence factor f e q. Since the definition of the equivalence factor depends on context, IUPAC, the SI unit for molality is mol/kg. The mole fraction x i is defined as the amount of a constituent n i divided by the amount of all constituents in a mixture n t o t, x i = n i n t o t. However, the deprecated parts-per notation is used to describe small mole fractions. The mole ratio r i is defined as the amount of a constituent n i divided by the amount of all other constituents in a mixture
8.
Density
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The density, or more precisely, the volumetric mass density, of a substance is its mass per unit volume. The symbol most often used for density is ρ, although the Latin letter D can also be used. Mathematically, density is defined as mass divided by volume, ρ = m V, where ρ is the density, m is the mass, and V is the volume. In some cases, density is defined as its weight per unit volume. For a pure substance the density has the numerical value as its mass concentration. Different materials usually have different densities, and density may be relevant to buoyancy, purity, osmium and iridium are the densest known elements at standard conditions for temperature and pressure but certain chemical compounds may be denser. Thus a relative density less than one means that the floats in water. The density of a material varies with temperature and pressure and this variation is typically small for solids and liquids but much greater for gases. Increasing the pressure on an object decreases the volume of the object, increasing the temperature of a substance decreases its density by increasing its volume. In most materials, heating the bottom of a results in convection of the heat from the bottom to the top. This causes it to rise relative to more dense unheated material, the reciprocal of the density of a substance is occasionally called its specific volume, a term sometimes used in thermodynamics. Density is a property in that increasing the amount of a substance does not increase its density. Archimedes knew that the irregularly shaped wreath could be crushed into a cube whose volume could be calculated easily and compared with the mass, upon this discovery, he leapt from his bath and ran naked through the streets shouting, Eureka. As a result, the term eureka entered common parlance and is used today to indicate a moment of enlightenment, the story first appeared in written form in Vitruvius books of architecture, two centuries after it supposedly took place. Some scholars have doubted the accuracy of this tale, saying among other things that the method would have required precise measurements that would have been difficult to make at the time, from the equation for density, mass density has units of mass divided by volume. As there are units of mass and volume covering many different magnitudes there are a large number of units for mass density in use. The SI unit of kilogram per metre and the cgs unit of gram per cubic centimetre are probably the most commonly used units for density.1,000 kg/m3 equals 1 g/cm3. In industry, other larger or smaller units of mass and or volume are often more practical, see below for a list of some of the most common units of density
9.
Evaporation
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Evaporation is a type of vaporization of a liquid that occurs from the surface of a liquid into a gaseous phase that is not saturated with the evaporating substance. The other type of vaporization is boiling, which is characterized by bubbles of saturated vapor forming in the liquid phase, steam produced in a boiler is another example of evaporation occurring in a saturated vapor phase. Evaporation that occurs directly from the solid phase below the melting point, on average, a fraction of the molecules in a glass of water have enough heat energy to escape from the liquid. The water in the glass will be cooled by the evaporation until an equilibrium is reached where the air supplies the amount of heat removed by the evaporating water, in an enclosed environment the water would evaporate until the air is saturated. With sufficient temperature, the liquid would turn into vapor quickly, when the molecules collide, they transfer energy to each other in varying degrees, based on how they collide. Sometimes the transfer is so one-sided for a molecule near the surface that it ends up with energy to escape. Evaporation is an part of the water cycle. The sun drives evaporation of water from oceans, lakes, moisture in the soil, in hydrology, evaporation and transpiration are collectively termed evapotranspiration. Evaporation of water occurs when the surface of the liquid is exposed, allowing molecules to escape and form water vapor, when only a small proportion of the molecules meet these criteria, the rate of evaporation is low. Since the kinetic energy of a molecule is proportional to its temperature, as the faster-moving molecules escape, the remaining molecules have lower average kinetic energy, and the temperature of the liquid decreases. This phenomenon is also called evaporative cooling and this is why evaporating sweat cools the human body. Evaporation also tends to proceed quickly with higher flow rates between the gaseous and liquid phase and in liquids with higher vapor pressure. For example, laundry on a line will dry more rapidly on a windy day than on a still day. Three key parts to evaporation are heat, atmospheric pressure, on a molecular level, there is no strict boundary between the liquid state and the vapor state. Instead, there is a Knudsen layer, where the phase is undetermined, because this layer is only a few molecules thick, at a macroscopic scale a clear phase transition interface cannot be seen. It is just that the process is slower and thus significantly less visible. If evaporation takes place in an area, the escaping molecules accumulate as a vapor above the liquid. Many of the return to the liquid, with returning molecules becoming more frequent as the density
10.
Atmospheric pressure
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Atmospheric pressure, sometimes also called barometric pressure, is the pressure exerted by the weight of air in the atmosphere of Earth. In most circumstances atmospheric pressure is approximated by the hydrostatic pressure caused by the weight of air above the measurement point. As elevation increases, there is less overlying atmospheric mass, so that atmospheric pressure decreases with increasing elevation. On average, a column of air one square centimetre in cross-section, measured from sea level to the top of the atmosphere, has a mass of about 1.03 kilograms and that force is a pressure of 10.1 N/cm2 or 101 kN/m2. A column 1 square inch in cross-section would have a weight of about 14.7 lb or about 65.4 N and it is modified by the planetary rotation and local effects such as wind velocity, density variations due to temperature and variations in composition. The standard atmosphere is a unit of pressure defined as 101325 Pa, the mean sea level pressure is the average atmospheric pressure at sea level. This is the pressure normally given in weather reports on radio, television. When barometers in the home are set to match the weather reports, they measure pressure adjusted to sea level. The altimeter setting in aviation, is an atmospheric pressure adjustment, average sea-level pressure is 1013.25 mbar. In aviation weather reports, QNH is transmitted around the world in millibars or hectopascals, except in the United States, Canada, however, in Canadas public weather reports, sea level pressure is instead reported in kilopascals. The highest sea-level pressure on Earth occurs in Siberia, where the Siberian High often attains a sea-level pressure above 1050 mbar, the lowest measurable sea-level pressure is found at the centers of tropical cyclones and tornadoes, with a record low of 870 mbar. Pressure varies smoothly from the Earths surface to the top of the mesosphere, although the pressure changes with the weather, NASA has averaged the conditions for all parts of the earth year-round. As altitude increases, atmospheric pressure decreases, one can calculate the atmospheric pressure at a given altitude. Temperature and humidity affect the atmospheric pressure, and it is necessary to know these to compute an accurate figure. The graph at right was developed for a temperature of 15 °C, at low altitudes above the sea level, the pressure decreases by about 1.2 kPa for every 100 meters. See pressure system for the effects of air pressure variations on weather, Atmospheric pressure shows a diurnal or semidiurnal cycle caused by global atmospheric tides. This effect is strongest in tropical zones, with an amplitude of a few millibars and these variations have two superimposed cycles, a circadian cycle and semi-circadian cycle. The highest adjusted-to-sea level barometric pressure recorded on Earth was 1085.7 hPa measured in Tosontsengel
11.
Water
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Water is a transparent and nearly colorless chemical substance that is the main constituent of Earths streams, lakes, and oceans, and the fluids of most living organisms. Its chemical formula is H2O, meaning that its molecule contains one oxygen, Water strictly refers to the liquid state of that substance, that prevails at standard ambient temperature and pressure, but it often refers also to its solid state or its gaseous state. It also occurs in nature as snow, glaciers, ice packs and icebergs, clouds, fog, dew, aquifers, Water covers 71% of the Earths surface. It is vital for all forms of life. Only 2. 5% of this water is freshwater, and 98. 8% of that water is in ice and groundwater. Less than 0. 3% of all freshwater is in rivers, lakes, and the atmosphere, a greater quantity of water is found in the earths interior. Water on Earth moves continually through the cycle of evaporation and transpiration, condensation, precipitation. Evaporation and transpiration contribute to the precipitation over land, large amounts of water are also chemically combined or adsorbed in hydrated minerals. Safe drinking water is essential to humans and other even though it provides no calories or organic nutrients. There is a correlation between access to safe water and gross domestic product per capita. However, some observers have estimated that by 2025 more than half of the population will be facing water-based vulnerability. A report, issued in November 2009, suggests that by 2030, in developing regions of the world. Water plays an important role in the world economy, approximately 70% of the freshwater used by humans goes to agriculture. Fishing in salt and fresh water bodies is a source of food for many parts of the world. Much of long-distance trade of commodities and manufactured products is transported by boats through seas, rivers, lakes, large quantities of water, ice, and steam are used for cooling and heating, in industry and homes. Water is an excellent solvent for a variety of chemical substances, as such it is widely used in industrial processes. Water is also central to many sports and other forms of entertainment, such as swimming, pleasure boating, boat racing, surfing, sport fishing, Water is a liquid at the temperatures and pressures that are most adequate for life. Specifically, at atmospheric pressure of 1 bar, water is a liquid between the temperatures of 273.15 K and 373.15 K
12.
Nucleation
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Nucleation is the first step in the formation of either a new thermodynamic phase or a new structure via self-assembly or self-organization. Nucleation is typically defined to be the process that determines how long an observer has to wait before the new phase or self-organized structure appears, nucleation is often found to be very sensitive to impurities in the system. Because of this, it is important to distinguish between heterogeneous nucleation and homogeneous nucleation. Heterogeneous nucleation occurs at sites on surfaces in the system. Homogeneous nucleation occurs away from a surface, nucleation is usually a stochastic process, so even in two identical systems nucleation will occur at different times. This behaviour is similar to radioactive decay, a common mechanism is illustrated in the animation to the right. This shows nucleation of a new phase in an existing phase and this nucleus of the red phase then grows and converts the system to this phase. The standard theory that describes this behaviour for the nucleation of a new phase is called classical nucleation theory. This is seen for example in the nucleation of ice in supercooled water droplets. The decay rate of the exponential gives the nucleation rate, classical nucleation theory is a widely used approximate theory for estimating these rates, and how they vary with variables such as temperature. It correctly predicts that the time you have to wait for nucleation decreases extremely rapidly when supersaturated and it is not just new phases such as liquids and crystals that form via nucleation followed by growth. The self-assembly process that forms objects like the amyloid aggregates associated with Alzheimers disease also starts with nucleation, energy consuming self-organising systems such as the microtubules in cells also show nucleation and growth. Clouds form when wet air cools and many small water droplets nucleate from the supersaturated air, the amount of water vapor that air can carry decreases with lower temperatures. The excess vapor begins to nucleate and to small water droplets which form a cloud. Nucleation of the droplets of water is heterogeneous, occurring on particles referred to as cloud condensation nuclei. Cloud seeding is the process of adding artificial condensation nuclei to quicken the formation of clouds, nucleation is the first step in crystallisation, so it determines if a crystal can form. Frequently crystals do not form even when they are thermodynamically the favored state, for example, small droplets of very pure water can remain liquid down to below -30 °C although ice is the stable state below 0 °C. Bubbles of carbon dioxide nucleate shortly after the pressure is released from a container of carbonated liquid, nucleation often occurs more easily at a pre-existing interface, as happens on boiling chips and on string used to make rock candy
13.
Heat index
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The result is also known as the felt air temperature or apparent temperature. For example, when the temperature is 32 °C with 70% relative humidity and this heat index temperature has an implied humidity of 20%. This is the value of relative humidity for which the heat index formula indicates 41 °C feels like 41 °C, a heat index temperature of 32 °C has an implied relative humidity of 38%. The human body cools itself by perspiration, or sweating. Heat is removed from the body by evaporation of that sweat, however, high relative humidity reduces the evaporation rate. This results in a rate of heat removal from the body. This results in an index that relates one combination of temperature. Also, for exercising or active, at the time. Plus when actively working, or not wearing a hat in sunny areas, hence, the heat index could seem unrealistically low, unless resting inactive in heavily shaded areas. The heat index was developed in 1978 by George Winterling as the humiture and was adopted by the USAs National Weather Service a year later and it is derived from work carried out by Robert G. Steadman. Significant deviations from these will result in heat index values which do not accurately reflect the perceived temperature, in Canada, the similar humidex is used in place of the heat index. A joint committee formed by the United States and Canada to resolve differences has since been disbanded, the heat index is referenced to any combination of air temperature and humidity where the partial pressure of water vapor is equal to a baseline value of 1.6 kilopascals. For example, this corresponds to an air temperature of 25 °C, at standard atmospheric pressure, this baseline also corresponds to a dew point of 14 °C and a mixing ratio of 0.01. A given value of relative humidity causes larger increases in the index at higher temperatures. It has been suggested that the equation described is only if the temperature is 27 °C or more. However, a recent analysis by iWeatherNet found the assumption to be given that the heat index/relative humidity relationship. The heat index and humidex figures are based on measurements taken in the shade and not the sun. The heat index also does not factor in the effects of wind, sometimes the heat index and the wind chill are denoted collectively by the single term apparent temperature, relative outdoor temperature, or feels like
14.
Saturation vapor density
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Saturation vapor density is a concept closely tied with saturation vapor pressure. It is useful for getting an exact quantity of vapor in the air from a relative humidity Given an RH percentage. Alternatively, RH can be found by RH = Actual Vapor Density ∕ SVD, as relative humidity is a dimensionless quantity, vapor density can be stated in units of grams or kilograms per cubic meter. The number of moles is related to density by n = M ∕ m, thus, setting V to 1 cubic meter, we get P m/R T = M/V = density. The values shown at hyperphysics-sources indicate that the vapor density is 4.85 g/m3 at 273 K. Therefore, for particular mole number and volume the saturated vapor pressure will not change if the temperature remains constant
15.
Water activity
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Water activity or aw is the partial vapor pressure of water in a substance divided by the standard state partial vapor pressure of water. In the field of science, the standard state is most often defined as the partial vapor pressure of pure water at the same temperature. Using this particular definition, pure distilled water has an activity of exactly one. As temperature increases, aw typically increases, except in some products with crystalline salt or sugar, higher aw substances tend to support more microorganisms. Bacteria usually require at least 0.91, and fungi at least 0.7, water migrates from areas of high aw to areas of low aw. For example, if honey is exposed to air, the honey absorbs water from the air. If salami is exposed to dry air, the salami dries out, definition of aw, a w ≡ p / p ∗ where p is the vapor pressure of water in the solution, and p*₀ is the vapor pressure of pure water at the same temperature. Alternate definition, a w ≡ l w x w where lw is the activity coefficient of water, relationship to relative humidity, The relative humidity of air in equilibrium with a sample is called the Equilibrium Relative Humidity. Food designers use water activity to formulate shelf-stable food, if a product is kept below a certain water activity, then mold growth is inhibited. This results in a shelf life. Water activity values can help limit moisture migration within a food product made with different ingredients. Food formulators use water activity to predict how much moisture migration affects their product, water activity is used in many cases as a critical control point for Hazard Analysis and Critical Control Points programs. Samples of the product are periodically taken from the production area. Measurements can be made in as little as five minutes, and are regularly in most major food production facilities. For many years, researchers tried to equate bacterial growth potential with water content and they found that the values were not universal, but specific to each food product. W. J. Scott first established that bacterial growth correlated with activity, not water content. It is firmly established that growth of bacteria is inhibited at specific water activity values, U. S. Food and Drug Administration regulations for intermediate moisture foods are based on these values. Lowering the water activity of a product should not be seen as a kill step
16.
Humidity indicator card
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A humidity indicator card is a card on which a moisture-sensitive chemical is impregnated such that it will change color when the indicated relative humidity is exceeded. This is usually blotting paper impregnated with cobalt chloride base, or less toxic and this item is an inexpensive way to quantify relative humidity levels inside sealed packaging. They are available in many configurations and used in applications, especially military. The most common humidity indicator cards change color from blue to pink, united States Military Specification Mil-I-8835A is the governing specification for a humidity indicator card. This is a joint standard developed by the Joint Electron Device Engineering Council, the need for an easily read humidity indicator that could not be damaged by vibration was identified during World War II. Blinn, at time the Commander of the USS Pope, became concerned about the poor condition of the weapons. High humidity in the South Pacific, coupled with poor packaging methods, was causing corrosion, a significant amount of ordnance was arriving in an unstable, and sometimes dangerous, condition. Following the end of the war Rear Admiral Blinn was assigned to Washington, there he developed the concept for the first color change humidity indicator, a simple “go/no-go” method of monitoring humidity. In the late 1940s, Relative Humidity in the range of 30-35% was the concern because this is when corrosion can begin, for 50 years, industrial and military applications for color change humidity indicators were the primary market for these products. This package delamination occurs as moisture within the package expands as a result of the rapid thermal changes experienced during solder mount operations. As a result, a wide standard for packaging of semiconductors was released in 1989. This standard, EIA583, called for the use of humidity indicator card that would indicate as low as 10%, in April 1999, J-STD-033 was released with a 5,10, 15% color change indicator card specified. In many cases this voids or changes the terms of warranty coverage for the device, cobalt-free brown to azure HICs can be found on the market. In 1998, the European Community issued a directive which classifies items containing cobalt chloride of 0.01 to 1% w/w as T, as a consequence, new cobalt-free humidity indicator cards have been developed by some companies. Although the EC issued this directive, it did not ban humidity indicators that contain cobalt chloride, the only effect the EC directive has on a humidity indicator card that contains cobalt chloride is setting labeling requirement thresholds. 25%. The T and R49 is not applicable because a humidity indicator cannot be inhaled, moisture sensitivity levels are indicated with a number as in the MSL list. JEDEC is the developer of standards for the solid-state industry. HICs are used to ensure that the humidity within dry packed barrier bags remains at levels for surface mount devices
17.
Hygrometer
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A hygrometer /haɪˈɡrɒmᵻtər/ is an instrument used for measuring the moisture content in the atmosphere. Humidity measurement instruments usually rely on measurements of some other quantity such as temperature, pressure, by calibration and calculation, these measured quantities can lead to a measurement of humidity. Modern electronic devices use temperature of condensation, or changes in electrical capacitance or resistance to measure humidity differences, the first crude hygrometer was invented by Leonardo da Vinci in 1480 and a more modern version was created by polymath Johann Heinrich Lambert in 1755. The metal-paper coil hygrometer is very useful for giving an indication of humidity changes. It appears most often in very inexpensive devices, and its accuracy is limited, in these devices, water vapour is absorbed by a salt-impregnated paper strip attached to a metal coil, causing the coil to change shape. These changes cause an indication on a dial and these devices use a human or animal hair under tension. The hair is hygroscopic, its length changes with humidity, in the late 1700s, such devices were called by some scientists hygroscopes, that word is no longer in current use, but hygroscopic and hygroscopy, which derive from it, still are. The traditional folk art known as a weather house works on this principle. Whale bone and other materials may be used in place of hair, in 1783, Swiss physicist and geologist Horace Bénédict de Saussure built the first hair-tension hygrometer using human hair. The pulley is connected to an index which moves over a graduated scale, the instrument can be made more sensitive by removing oils from the hair, such as by first soaking the hair in diethyl ether. A psychrometer, or wet-and-dry-bulb thermometer, consists of two thermometers, one that is dry and one that is kept moist with distilled water on a sock or wick. When the air temperature is below freezing, however, the wet-bulb is covered with a coating of ice. Relative humidity is computed from the ambient temperature as shown by the dry-bulb thermometer, relative humidity can also be determined by locating the intersection of the wet and dry-bulb temperatures on a psychrometric chart. The two thermometers coincide when the air is saturated, and the greater the difference the drier the air. Psychrometers are commonly used in meteorology, and in the HVAC industry for proper refrigerant charging of residential and commercial air conditioning systems, a whirling psychrometer uses the same principle, but the two thermometers are fitted into a device that resembles a ratchet or football rattle. Dew point is the temperature at which a sample of moist air at constant pressure reaches water vapor saturation, at this saturation temperature, further cooling results in condensation of water. Chilled mirror dewpoint hygrometers are some of the most precise instruments commonly available and they use a chilled mirror and optoelectronic mechanism to detect condensation on the mirrors surface. The temperature of the mirror is controlled by electronic feedback to maintain an equilibrium between evaporation and condensation, thus closely measuring the dew point temperature
18.
Dry-bulb temperature
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The dry-bulb temperature is the temperature of air measured by a thermometer freely exposed to the air but shielded from radiation and moisture. DBT is the temperature that is thought of as air temperature. It indicates the amount of heat in the air and is proportional to the mean kinetic energy of the air molecules. Temperature is usually measured in degrees Celsius, Kelvin, or Fahrenheit, unlike wet bulb temperature, dry bulb temperature does not indicate the amount of moisture in the air. In construction, it is an important consideration when designing a building for a certain climate, nall called it one of the most important climate variables for human comfort and building energy efficiency. DBT is an important variable in Psychrometrics, being the horizontal axis of a Psychrometric chart, Psychrometric chart Wet-bulb temperature Hygrometer Atmospheric thermodynamics
19.
Wet-bulb temperature
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The wet-bulb temperature is the temperature a parcel of air would have if it were cooled to saturation by the evaporation of water into it, with the latent heat being supplied by the parcel. A wet-bulb thermometer will indicate a close to the true wet-bulb temperature. The wet-bulb temperature is the lowest temperature that can be reached under current ambient conditions by the evaporation of water only, wet-bulb temperature is largely determined by both actual air temperature and the amount of moisture in the air. At 100% relative humidity, the wet-bulb temperature equals the dry-bulb temperature, the thermodynamic wet-bulb temperature is the lowest temperature which may be achieved by evaporative cooling of a water-wetted, ventilated surface. For a parcel of air that is less saturated, the wet-bulb temperature is lower than the dry-bulb temperature. The lower the humidity, the greater the gaps between each pair of these three temperatures. Conversely, when the humidity rises to 100%, the three figures coincide. For air at a pressure and dry-bulb temperature, the thermodynamic wet-bulb temperature corresponds to unique values of the relative humidity. It therefore may be used for the determination of these values. The relationships between these values are illustrated in a psychrometric chart, cooling of the human body through perspiration is inhibited as the wet-bulb temperature of the surrounding air increases in summer. Other mechanisms may be at work in winter if there is validity to the notion of a humid or damp cold, meteorologists and others may use the term isobaric wet-bulb temperature to refer to the thermodynamic wet-bulb temperature. Thermodynamic wet-bulb temperature is plotted on a psychrometric chart, the thermodynamic wet-bulb temperature is a thermodynamic property of a mixture of air and water vapor. The value indicated by a simple wet-bulb thermometer often provides an approximation of the thermodynamic wet-bulb temperature. For an accurate thermometer, the wet-bulb temperature and the adiabatic saturation temperature are approximately equal for air-water vapor mixtures at atmospheric temperature and pressure. This is not necessarily true at temperatures and pressures that deviate significantly from ordinary atmospheric conditions, wet-bulb temperature is measured using a thermometer that has its bulb wrapped in cloth—called a sock—that is kept wet with distilled water via wicking action. Such an instrument is called a wet-bulb thermometer, the thermometers are attached to a swivelling handle which allows them to be whirled around so that water evaporates from the sock and cools the wet bulb until it reaches thermal equilibrium. An actual wet-bulb thermometer reads a temperature that is different from the thermodynamic wet-bulb temperature. This is due to a coincidence, for a system the psychrometric ratio happens to be close to 1, although for systems other than air
20.
Garden Society of Gothenburg
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The Garden Society of Gothenburg is a park and horticultural garden in central Gothenburg, Sweden. It is located next to Kungsportsavenyen, the park was founded in 1842 by King Carl XIV Johan, on initiative of the amateur botanist Henric Elof von Normann. In the park there is a rose garden with some 4,000 roses of 1,900 species. The rose garden has been awarded stars in the Michelin Green Guide, there is also a 19th-century palm house, greenhouses, sculptures, a restaurant and cafés. It is one of the best preserved 19th century parks in Sweden
21.
Condensation
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Condensation is the change of the physical state of matter from gas phase into liquid phase, and is the reverse of evaporation. The word most often refers to the water cycle and it can also be defined as the change in the state of water vapour to liquid water when in contact with a liquid or solid surface or cloud condensation nuclei within the atmosphere. When the transition happens from the phase into the solid phase directly. A few distinct reversibility scenarios emerge here with respect to the nature of the surface, absorption into the surface of a liquid —is reversible as evaporation. Adsorption onto solid surface at pressures and temperatures higher than the species triple point—also reversible as evaporation, adsorption onto solid surface at pressures and temperatures lower than the species triple point—is reversible as sublimation. Condensation commonly occurs when a vapor is cooled and/or compressed to its limit when the molecular density in the gas phase reaches its maximal threshold. Vapor cooling and compressing equipment that collects condensed liquids is called a condenser, psychrometry measures the rates of condensation through evaporation into the air moisture at various atmospheric pressures and temperatures. Water is the product of its vapor condensation—condensation is the process of such phase conversion, condensation is a crucial component of distillation, an important laboratory and industrial chemistry application. Because condensation is a naturally occurring phenomenon, it can often be used to water in large quantities for human use. Many structures are made solely for the purpose of collecting water from condensation, such as air wells and it is also a crucial process in forming particle tracks in a cloud chamber. In this case, ions produced by an incident particle act as centers for the condensation of the vapor producing the visible cloud trails. Furthermore, condensation is a step in many industrial processes, such as power generation, water desalination, thermal management, refrigeration. Numerous living beings use water made accessible by condensation, a few examples of these are the Australian Thorny Devil, the darkling beetles of the Namibian coast, and the Coast Redwoods of the West Coast of the United States. To alleviate these issues, the air humidity needs to be lowered. This can be done in a number of ways, for example opening windows, turning on extractor fans, using dehumidifiers, drying clothes outside and covering pots and pans whilst cooking. Air conditioning or ventilation systems can be installed that help remove moisture from the air, the amount of water vapour that can be stored in the air can be increased simply by increasing the temperature. However, this can be a double edged sword as most condensation in the home occurs when warm, as the air is cooled, it can no longer hold as much water vapour. This leads to deposition of water on the cool surface and this is very apparent when central heating is used in combination with single glazed windows in winter
22.
Thermal radiation
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Thermal radiation is electromagnetic radiation generated by the thermal motion of charged particles in matter. All matter with a greater than absolute zero emits thermal radiation. When the temperature of a body is greater than absolute zero, Thermal radiation is different from thermal convection and thermal conduction—a person near a raging bonfire feels radiant heating from the fire, even if the surrounding air is very cold. Sunlight is part of thermal radiation generated by the hot plasma of the Sun, the Earth also emits thermal radiation, but at a much lower intensity and different spectral distribution because it is cooler. The Earths absorption of radiation, followed by its outgoing thermal radiation are the two most important processes that determine the temperature and climate of the Earth. If a radiation-emitting object meets the physical characteristics of a body in thermodynamic equilibrium. Plancks law describes the spectrum of radiation, which depends only on the objects temperature. Wiens displacement law determines the most likely frequency of the radiation. Thermal radiation is one of the mechanisms of heat transfer. Thermal radiation is the emission of electromagnetic waves from all matter that has a greater than absolute zero. It represents a conversion of energy into electromagnetic energy. Thermal energy consists of the energy of random movements of atoms. All matter with a temperature by definition is composed of particles which have kinetic energy, and these atoms and molecules are composed of charged particles, i. e. protons and electrons, and kinetic interactions among matter particles result in charge-acceleration and dipole-oscillation. This results in the generation of coupled electric and magnetic fields, resulting in the emission of photons. Electromagnetic radiation, including light, does not require the presence of matter to propagate, the radiation is not monochromatic, i. e. it does not consist of just a single frequency, but comprises a continuous dispersion of photon energies, its characteristic spectrum. If the radiating body and its surface are in thermodynamic equilibrium, a black body is also a perfect emitter. The radiation of such perfect emitters is called black-body radiation, the ratio of any bodys emission relative to that of a black body is the bodys emissivity, so that a black body has an emissivity of unity. Absorptivity, reflectivity, and emissivity of all bodies are dependent on the wavelength of the radiation, the temperature determines the wavelength distribution of the electromagnetic radiation
23.
Frost
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Frost is the coating or deposit of ice that may form in humid air in cold conditions, usually overnight. In temperate climates it most commonly appears as white crystals or frozen dew drops near the ground. Frost is composed of delicate branched patterns of ice crystals formed as the result of fractal process development, Frost is known to damage crops or reduce future crop yields, therefore farmers in those regions where frost is a problem often invest substantial means to prevent its formation. In most temperate countries such temperatures usually are the result of loss by radiation at night. The size of frost crystals varies depending on the time they have been building up, Frost crystals may be clear or translucent, but, like snow, a mass of frost crystals will scatter light in all directions, so that a coating of frost appears white. If a solid surface is chilled below the dew point of the humid air. If the water deposits as a liquid that freezes, it forms a coating that may look glassy, opaque, or crystalline. Depending on context, that also may be called atmospheric icing. The ice it produces differs in ways from crystalline frost. For desublimation to proceed the surface must be below the frost point of the air, the air must be humid, but not sufficiently humid to permit the condensation of liquid water, or icing will result instead of desublimation. The size of the crystals depends largely on the temperature, the amount of water vapor available, as a rule, except in conditions where supercooled droplets are present in the air, frost will form only if the deposition surface is colder than the surrounding air. For instance frost may be observed around cracks in cold wooden sidewalks when humid air escapes from the ground beneath. Other objects on which frost commonly forms are those with low specific heat or high thermal emissivity, such as blackened metals, the apparently erratic occurrence of frost in adjacent localities is due partly to differences of elevation, the lower areas becoming colder on calm nights. Where static air settles above an area of ground in the absence of wind, hoar frost refers to white ice crystals, deposited on the ground or loosely attached to exposed objects such as wires or leaves. They form on cold, clear nights when conditions are such that heat radiates out to the sky faster than it can be replaced from nearby sources such as wind or warm objects. Under suitable circumstances, objects cool to below the frost point of the surrounding air, such freezing may be promoted by effects such as flood frost or frost pocket. These occur when ground-level radiation losses cool air till it flows downhill and accumulates in pockets of cold air in valleys. Hoar frost may freeze in such low-lying cold air even when the air temperature a few feet above ground is well above freezing
24.
Guttation
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Guttation is the exudation of drops of xylem sap on the tips or edges of leaves of some vascular plants, such as grasses. Guttation is not to be confused with dew, which condenses from the atmosphere onto the plant surface, at night, transpiration usually does not occur because most plants have their stomata closed. When there is a soil moisture level, water will enter plant roots. The water will accumulate in the plant, creating a slight root pressure, the root pressure forces some water to exude through special leaf tip or edge structures, hydathodes or water glands, forming drops. Root pressure provides the impetus for this flow, rather than transpirational pull, guttation is most noticeable when transpiration is suppressed and the relative humidity is high, such as during the night. Guttation fluid may contain a variety of organic and inorganic compounds, mainly sugars, on drying, a white crust remains on the leaf surface. Concentrations this high are near those of active ingredients applied in field sprays for pest control and it was found that when bees consume guttation drops collected from plants grown from neonicotinoid-coated seeds, they die within a few minutes. This phenomenon may be a factor in bee deaths and, consequently, if high levels of nitrogen appear in the fluid, it is a sign of fertilizer burn. Excess nitrogen must be leached from the soil by addition of large quantities of water and this is the best way to restore soil fertility, but it may result in water pollution. Homeostasis Osmosis Soil plant atmosphere continuum Transpiration
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Temperature
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A temperature is an objective comparative measurement of hot or cold. It is measured by a thermometer, several scales and units exist for measuring temperature, the most common being Celsius, Fahrenheit, and, especially in science, Kelvin. Absolute zero is denoted as 0 K on the Kelvin scale, −273.15 °C on the Celsius scale, the kinetic theory offers a valuable but limited account of the behavior of the materials of macroscopic bodies, especially of fluids. Temperature is important in all fields of science including physics, geology, chemistry, atmospheric sciences, medicine. The Celsius scale is used for temperature measurements in most of the world. Because of the 100 degree interval, it is called a centigrade scale.15, the United States commonly uses the Fahrenheit scale, on which water freezes at 32°F and boils at 212°F at sea-level atmospheric pressure. Many scientific measurements use the Kelvin temperature scale, named in honor of the Scottish physicist who first defined it and it is a thermodynamic or absolute temperature scale. Its zero point, 0K, is defined to coincide with the coldest physically-possible temperature and its degrees are defined through thermodynamics. The temperature of zero occurs at 0K = −273. 15°C. For historical reasons, the triple point temperature of water is fixed at 273.16 units of the measurement increment, Temperature is one of the principal quantities in the study of thermodynamics. There is a variety of kinds of temperature scale and it may be convenient to classify them as empirically and theoretically based. Empirical temperature scales are historically older, while theoretically based scales arose in the middle of the nineteenth century, empirically based temperature scales rely directly on measurements of simple physical properties of materials. For example, the length of a column of mercury, confined in a capillary tube, is dependent largely on temperature. Such scales are only within convenient ranges of temperature. For example, above the point of mercury, a mercury-in-glass thermometer is impracticable. A material is of no use as a thermometer near one of its phase-change temperatures, in spite of these restrictions, most generally used practical thermometers are of the empirically based kind. Especially, it was used for calorimetry, which contributed greatly to the discovery of thermodynamics, nevertheless, empirical thermometry has serious drawbacks when judged as a basis for theoretical physics. Theoretically based temperature scales are based directly on theoretical arguments, especially those of thermodynamics, kinetic theory and they rely on theoretical properties of idealized devices and materials
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Precipitation
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In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls under gravity. The main forms of precipitation include drizzle, rain, sleet, snow, graupel, Precipitation occurs when a portion of the atmosphere becomes saturated with water vapor, so that the water condenses and precipitates. Thus, fog and mist are not precipitation but suspensions, because the vapor does not condense sufficiently to precipitate. Two processes, possibly acting together, can lead to air becoming saturated, Precipitation forms as smaller droplets coalesce via collision with other rain drops or ice crystals within a cloud. Short, intense periods of rain in scattered locations are called showers, moisture that is lifted or otherwise forced to rise over a layer of sub-freezing air at the surface may be condensed into clouds and rain. This process is active when freezing rain is occurring. A stationary front is often present near the area of freezing rain, provided necessary and sufficient atmospheric moisture content, the moisture within the rising air will condense into clouds, namely stratus and cumulonimbus. Eventually, the droplets will grow large enough to form raindrops. Lake-effect snowfall can be locally heavy, thundersnow is possible within a cyclones comma head and within lake effect precipitation bands. In mountainous areas, heavy precipitation is possible where upslope flow is maximized within windward sides of the terrain at elevation, on the leeward side of mountains, desert climates can exist due to the dry air caused by compressional heating. The movement of the trough, or intertropical convergence zone. Precipitation is a component of the water cycle, and is responsible for depositing the fresh water on the planet. Approximately 505,000 cubic kilometres of water falls as precipitation each year,398,000 cubic kilometres of it over the oceans and 107,000 cubic kilometres over land. Given the Earths surface area, that means the globally averaged annual precipitation is 990 millimetres, Climate classification systems such as the Köppen climate classification system use average annual rainfall to help differentiate between differing climate regimes. Precipitation may occur on celestial bodies, e. g. when it gets cold, Mars has precipitation which most likely takes the form of frost. Precipitation is a component of the water cycle, and is responsible for depositing most of the fresh water on the planet. Approximately 505,000 km3 of water falls as precipitation each year,398,000 km3 of it over the oceans, given the Earths surface area, that means the globally averaged annual precipitation is 990 millimetres. Mechanisms of producing precipitation include convective, stratiform, and orographic rainfall, Precipitation can be divided into three categories, based on whether it falls as liquid water, liquid water that freezes on contact with the surface, or ice
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Cloud condensation nuclei
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Cloud condensation nuclei or CCNs are small particles typically 0.2 µm, or 1/100th the size of a cloud droplet on which water vapour condenses. Water requires a surface to make the transition from a vapour to a liquid. In the atmosphere, this presents itself as tiny solid or liquid particles called CCNs. When no CCNs are present, water vapour can be supercooled at about -13°C for 5-6 hours before droplets spontaneously form, in above freezing temperatures the air would have to be supersaturated to around 400% before the droplets could form. The concept of condensation nuclei is used in cloud seeding. It has further suggested that creating such nuclei could be used for marine cloud brightening. The number of cloud condensation nuclei in the air can be measured, the total mass of CCNs injected into the atmosphere has been estimated at 2x1012 kg over a years time. There are many different types of atmospheric particulates that can act as CCN, sulfate and sea salt, for instance, readily absorb water whereas soot, organic carbon and mineral particles do not. This is made more complicated by the fact that many of the chemical species may be mixed within the particles. Additionally, while some particles do not make very good CCN, there is also speculation that solar variation may affect cloud properties via CCNs, and hence affect climate. These sulfate aerosols form partly from the dimethyl sulfide produced by phytoplankton in the open ocean, large algal blooms in ocean surface waters occur in a wide range of latitudes and contribute considerable DMS into the atmosphere to act as nuclei. The idea that an increase in temperature would also increase phytoplankton activity. An increase of phytoplankton has been observed by scientists in certain areas, a counter-hypothesis is advanced in The Revenge of Gaia, the book by James Lovelock. Warming oceans are likely to become stratified, with most ocean nutrients trapped in the bottom layers while most of the light needed for photosynthesis in the warm top layer. Under this scenario, deprived of nutrients, marine phytoplankton would decline, as would sulfate cloud condensation nuclei, and this is known as the CLAW hypothesis but no conclusive evidence to support this has yet been reported. Bergeron process Evapotranspiration Global dimming Seed crystal Water cycle www. grida. no
28.
Fog
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Fog consists of visible cloud water droplets or ice crystals suspended in the air at or near the Earths surface. Fog can be considered a type of low-lying cloud and is influenced by nearby bodies of water, topography. In turn, fog has affected many human activities, such as shipping, travel, the term fog is typically distinguished from the more generic term cloud in that fog is low-lying, and the moisture in the fog is often generated locally. By definition, fog reduces visibility to less than 1 kilometre, for aviation purposes in the UK, a visibility of less than 5 kilometres but greater than 999 metres is considered to be mist if the relative humidity is 70% or greater, below 70%, haze is reported. Fog forms when the difference between air temperature and dew point is less than 2.5 °C or 4 °F, Fog begins to form when water vapor condenses into tiny liquid water droplets suspended in the air. Water vapor normally begins to condense on condensation nuclei such as dust, ice, Fog, like its elevated cousin stratus, is a stable cloud deck which tends to form when a cool, stable air mass is trapped underneath a warm air mass. Fog normally occurs at a relative humidity near 100% and this occurs from either added moisture in the air, or falling ambient air temperature. However, fog can form at lower humidities, and can fail to form with relative humidity at 100%. At 100% relative humidity, the air cannot hold additional moisture, thus, Fog can form suddenly and can dissipate just as rapidly. The sudden formation of fog is known as flash fog, Fog commonly produces precipitation in the form of drizzle or very light snow. Drizzle occurs when the humidity of fog attains 100% and the cloud droplets begin to coalesce into larger droplets. This can occur when the fog layer is lifted and cooled sufficiently, drizzle becomes freezing drizzle when the temperature at the surface drops below the freezing point. The inversion boundary varies its altitude primarily in response to the weight of the air above it, the marine layer, and any fogbank it may contain, will be squashed when the pressure is high, and conversely, may expand upwards when the pressure above it is lowering. Fog can form in a number of ways, depending on how the cooling that caused the condensation occurred, radiation fog is formed by the cooling of land after sunset by thermal radiation in calm conditions with clear sky. The warm ground produces condensation in the air by heat conduction. In perfect calm the fog layer can be less than a meter deep, radiation fogs occur at night, and usually do not last long after sunrise, but they can persist all day in the winter months especially in areas bounded by high ground. Radiation fog is most common in autumn and early winter, examples of this phenomenon include the Tule fog. Ground fog is fog that obscures less than 60% of the sky, advection fog occurs when moist air passes over a cool surface by advection and is cooled
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Infrared
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It extends from the nominal red edge of the visible spectrum at 700 nanometers, to 1000000 nm. Most of the radiation emitted by objects near room temperature is infrared. Like all EMR, IR carries radiant energy, and behaves both like a wave and like its quantum particle, the photon, slightly more than half of the total energy from the Sun was eventually found to arrive on Earth in the form of infrared. The balance between absorbed and emitted infrared radiation has an effect on Earths climate. Infrared radiation is emitted or absorbed by molecules when they change their rotational-vibrational movements and it excites vibrational modes in a molecule through a change in the dipole moment, making it a useful frequency range for study of these energy states for molecules of the proper symmetry. Infrared spectroscopy examines absorption and transmission of photons in the infrared range, Infrared radiation is used in industrial, scientific, and medical applications. Night-vision devices using active near-infrared illumination allow people or animals to be observed without the observer being detected, Infrared thermal-imaging cameras are used to detect heat loss in insulated systems, to observe changing blood flow in the skin, and to detect overheating of electrical apparatuses. Thermal-infrared imaging is used extensively for military and civilian purposes, military applications include target acquisition, surveillance, night vision, homing, and tracking. Humans at normal body temperature radiate chiefly at wavelengths around 10 μm, Infrared radiation extends from the nominal red edge of the visible spectrum at 700 nanometers to 1 mm. This range of wavelengths corresponds to a range of approximately 430 THz down to 300 GHz. Below infrared is the portion of the electromagnetic spectrum. Sunlight, at a temperature of 5,780 kelvins, is composed of near thermal-spectrum radiation that is slightly more than half infrared. At zenith, sunlight provides an irradiance of just over 1 kilowatt per square meter at sea level, of this energy,527 watts is infrared radiation,445 watts is visible light, and 32 watts is ultraviolet radiation. Nearly all the radiation in sunlight is near infrared, shorter than 4 micrometers. On the surface of Earth, at far lower temperatures than the surface of the Sun, almost all thermal radiation consists of infrared in mid-infrared region, much longer than in sunlight. Of these natural thermal radiation processes only lightning and natural fires are hot enough to produce much visible energy, thermal infrared radiation also has a maximum emission wavelength, which is inversely proportional to the absolute temperature of object, in accordance with Wiens displacement law. Therefore, the band is often subdivided into smaller sections. Due to the nature of the blackbody radiation curves, typical hot objects, such as exhaust pipes, the three regions are used for observation of different temperature ranges, and hence different environments in space
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Radiation
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In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or through a material medium. Radiation is often categorized as either ionizing or non-ionizing depending on the energy of the radiated particles, Ionizing radiation carries more than 10 eV, which is enough to ionize atoms and molecules, and break chemical bonds. This is an important distinction due to the difference in harmfulness to living organisms. A common source of ionizing radiation is radioactive materials that emit α, β, or γ radiation, consisting of helium nuclei, electrons or positrons, gamma rays, X-rays and the higher energy range of ultraviolet light constitute the ionizing part of the electromagnetic spectrum. The lower-energy, longer-wavelength part of the spectrum including visible light, infrared light, microwaves and this type of radiation only damages cells if the intensity is high enough to cause excessive heating. Ultraviolet radiation has some features of both ionizing and non-ionizing radiation and these properties derive from ultraviolets power to alter chemical bonds, even without having quite enough energy to ionize atoms. The word radiation arises from the phenomenon of waves radiating from a source and this aspect leads to a system of measurements and physical units that are applicable to all types of radiation. This law does not apply close to a source of radiation or for focused beams. Radiation with sufficiently high energy can ionize atoms, that is to say it can knock electrons off atoms, ionization occurs when an electron is stripped from an electron shell of the atom, which leaves the atom with a net positive charge. Because living cells and, more importantly, the DNA in those cells can be damaged by this ionization, thus ionizing radiation is somewhat artificially separated from particle radiation and electromagnetic radiation, simply due to its great potential for biological damage. While an individual cell is made of trillions of atoms, only a fraction of those will be ionized at low to moderate radiation powers. If the source of the radiation is a radioactive material or a nuclear process such as fission or fusion. Particle radiation is subatomic particles accelerated to relativistic speeds by nuclear reactions, because of their momenta they are quite capable of knocking out electrons and ionizing materials, but since most have an electrical charge, they dont have the penetrating power of ionizing radiation. The exception is neutron particles, see below, there are several different kinds of these particles, but the majority are alpha particles, beta particles, neutrons, and protons. Roughly speaking, photons and particles with energies above about 10 electron volts are ionizing, particle radiation from radioactive material or cosmic rays almost invariably carries enough energy to be ionizing. The radiation is invisible and not directly detectable by human senses, as a result, in some cases, it may lead to secondary emission of visible light upon its interaction with matter, as in the case of Cherenkov radiation and radio-luminescence. Ionizing radiation has many uses in medicine, research and construction. Ultraviolet, of wavelengths from 10 nm to 125 nm, ionizes air molecules, causing it to be absorbed by air
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Solar radiation
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Solar irradiance is the power per unit area received from the Sun in the form of electromagnetic radiation in the wavelength range of the measuring instrument. Irradiance may be measured in space or at the Earths surface after atmospheric absorption and it is measured perpendicular to the incoming sunlight. Total solar irradiance, is a measure of the power over all wavelengths per unit area incident on the Earths upper atmosphere. The solar constant is a measure of mean TSI at a distance of one astronomical Unit. Irradiance is a function of distance from the Sun, the solar cycle, Irradiance on Earth is also measured perpendicular to the incoming sunlight. Insolation is the received on Earth per unit area on a horizontal surface. It depends on the height of the Sun above the horizon, the solar irradiance integrated over time is called solar irradiation, solar exposure or insolation. However, insolation is often used interchangeably with irradiance in practice, the SI unit of irradiance is watt per square meter. An alternate unit of measure is the Langley per unit time, the solar energy industry uses watt-hour per square metre per unit time, the relation to the SI unit is thus 1 kW/m2 =24 kWh/m2/day =8760 kWh/m2/year. Irradiance can also be expressed in Suns, where one Sun equals 1000 W/m2 at the point of arrival, part of the radiation reaching an object is absorbed and the remainder reflected. Usually the absorbed radiation is converted to energy, increasing the objects temperature. Manmade or natural systems, however, can convert part of the radiation into another form such as electricity or chemical bonds. The proportion of reflected radiation is the objects reflectivity or albedo, insolation onto a surface is largest when the surface directly faces the sun. As the angle between the surface and the Sun moves from normal, the insolation is reduced in proportion to the angles cosine, see effect of sun angle on climate. In the figure, the angle shown is between the ground and the rather than between the vertical direction and the sunbeam, hence the sine rather than the cosine is appropriate. A sunbeam one mile wide arrives from directly overhead, and another at a 30° angle to the horizontal, the sine of a 30° angle is 1/2, whereas the sine of a 90° angle is 1. Therefore, the angled sunbeam spreads the light over twice the area, consequently, half as much light falls on each square mile. This projection effect is the reason why Earths polar regions are much colder than equatorial regions
32.
Thermal conductivity
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In physics, thermal conductivity is the property of a material to conduct heat. It is evaluated primarily in terms of Fouriers Law for heat conduction, heat transfer occurs at a lower rate across materials of low thermal conductivity than across materials of high thermal conductivity. Correspondingly, materials of high thermal conductivity are used in heat sink applications. The thermal conductivity of a material may depend on temperature, the reciprocal of thermal conductivity is called thermal resistivity. Thermal conductivity is actually a tensor, which means it is possible to have different values in different directions, in SI units, thermal conductivity is measured in watts per meter-kelvin. The dimension of thermal conductivity is M1L1T−3Θ−1 and these variables are mass, length, time, and temperature. In Imperial units, thermal conductivity is measured in BTU/, other units which are closely related to the thermal conductivity are in common use in the construction and textile industries. The construction industry makes use of such as the R-value. Although related to the conductivity of a material used in an insulation product, R-. Likewise the textile industry has several units including the tog and the clo which express thermal resistance of a material in a way analogous to the R-values used in the construction industry, there are a number of ways to measure thermal conductivity. Each of these is suitable for a range of materials, depending on the thermal properties. There is a distinction between steady-state and transient techniques, in general, steady-state techniques are useful when the temperature of the material does not change with time. This makes the signal analysis straightforward, the disadvantage is that a well-engineered experimental setup is usually needed. The Divided Bar is the most common used for consolidated rock solids. Thermal conductivity is important in science, research, electronics, building insulation and related fields. Several materials are shown in the list of thermal conductivities and these should be considered approximate due to the uncertainties related to material definitions. High energy generation rates within electronics or turbines require the use of materials with high thermal conductivity such as copper, aluminium, the reciprocal of thermal conductivity is thermal resistivity, usually expressed in kelvin-meters per watt. For a given thickness of a material, that particular constructions thermal resistance, unfortunately, there are differing definitions for these terms
33.
Distillation
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Distillation is a process of separating the component or substances from a liquid mixture by selective evaporation and condensation. Distillation may result in complete separation, or it may be a partial separation that increases the concentration of selected components of the mixture. In either case the process exploits differences in the volatility of the mixtures components, in industrial chemistry, distillation is a unit operation of practically universal importance, but it is a physical separation process and not a chemical reaction. For example, In the fossil fuel industry distillation is a class of operation in obtaining materials from crude oil for fuels. Distillation permits separation of air into its components — notably oxygen, nitrogen, Distillation of fermented products produces distilled beverages with a high alcohol content, or separates out other fermentation products of commercial value. An installation for distillation, especially of alcohol, is a distillery, the distillation equipment is a still. Distillation is an old method of artificial desalination. Aristotle wrote about the process in his Meteorologica and even that ordinary wine possesses a kind of exhalation, later evidence of distillation comes from Greek alchemists working in Alexandria in the 1st century AD. Distilled water has been known since at least c,200, when Alexander of Aphrodisias described the process. Work on distilling other liquids continued in early Byzantine Egypt under the Greek-Egyptian Zosimus of Panopolis, Distillation in China could have begun during the Eastern Han Dynasty, but archaeological evidence indicates that actual distillation of beverages began in the Jin and Southern Song dynasties. A still was found in a site in Qinglong, Hebei province dating to the 12th century. Distilled beverages were more common during the Yuan dynasty, arabs learned the process from the Alexandrians and used it extensively in their chemical experiments. Clear evidence of the distillation of alcohol comes from the School of Salerno in the 12th century, fractional distillation was developed by Tadeo Alderotti in the 13th century. In 1500, German alchemist Hieronymus Braunschweig published Liber de arte destillandi the first book dedicated to the subject of distillation. In 1651, John French published The Art of Distillation the first major English compendium of practice and this includes diagrams with people in them showing the industrial rather than bench scale of the operation. As alchemy evolved into the science of chemistry, vessels called retorts became used for distillations, riveted joints were often kept tight by using various mixtures, for instance a dough made of rye flour. These alembics often featured a system around the beak, using cold water for instance. Today, the retorts and pot stills have largely supplanted by more efficient distillation methods in most industrial processes
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Lysimeter
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A lysimeter is a measuring device which can be used to measure the amount of actual evapotranspiration which is released by plants. By recording the amount of precipitation that an area receives and the amount lost through the soil, lysimeters are of two types, weighing and non-weighing. A lysimeter is most accurate when vegetation is grown in a large soil tank which allows the rainfall input, the amount of water lost by evapotranspiration can be worked out by calculating the difference between the weight before and after the precipitation input. But for farm crops, a lysimeter can represent field conditions well since the device is installed and used outside the laboratory. A weighing lysimeter, for example, reveals the amount of crops use by constantly weighing a huge block of soil in a field to detect losses of soil moisture. In 1875 Edward Lewis Sturtevant, a botanist from Massachusetts, built the first lysimeter in the United States
35.
Earth's energy budget
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Earths energy budget accounts for the energy Earth receives from the Sun. Much of this energy is lost when the earth re-radiates it back into space. This system is made up of water, ice, atmosphere, rocky crust. Quantifying changes in these amounts is required to model the Earths climate. Received radiation is distributed over the planet, because the Sun heats equatorial regions more than polar regions. When the incoming energy is balanced by an equal flow of heat to space. Disturbances of Earths radiative equilibrium, such as an increase of greenhouse gases, however, Earths energy balance and heat fluxes depend on many factors, such as atmospheric composition, the albedo of surface properties, cloud cover and vegetation and land use patterns. Changes in surface temperature due to Earths energy budget do not occur instantaneously, due to the inertia of the oceans and the cryosphere. The net heat flux is buffered primarily by becoming part of the heat content. To quantify Earths heat budget or heat balance, let the insolation received at the top of the atmosphere be 100 units, as shown in the accompanying illustration. Called the albedo of Earth, around 35 units are reflected back to space,27 from the top of clouds,2 from snow and ice-covered areas, the 65 remaining units are absorbed,14 within the atmosphere and 51 by the Earth’s surface. These 51 units are radiated to space in the form of radiation,17 directly radiated to space and 34 absorbed by the atmosphere. The 48 units absorbed by the atmosphere are finally radiated back to space and these 65 units balance the 65 units absorbed from the sun, thereby demonstrating no net gain of energy by the Earth. The total amount of energy received per second at the top of Earths atmosphere is measured in watts and is given by the solar constant times the area of the Earth. Because the surface area of a sphere is four times the surface area of a sphere. Since the absorption varies with location as well as with diurnal, seasonal and annual variations and this gives the earth a mean net albedo of 0.29. The geothermal heat flux from the Earths interior is estimated to be 47 terawatts and this comes to 0.087 watt/square metre, which represents only 0. 027% of Earths total energy budget at the surface, which is dominated by 173,000 terawatts of incoming solar radiation. Earlier, Joseph Fourier had claimed that deep space radiation was significant in an often cited as the first on the greenhouse effect
36.
Atacama Desert
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The Atacama Desert is a plateau in South America, covering a 1, 000-kilometre strip of land on the Pacific coast, west of the Andes mountains. It is the driest non-polar desert in the world, according to estimates, the Atacama Desert proper occupies 105,000 square kilometres, or 128,000 square kilometres if the barren lower slopes of the Andes are included. Most of the desert is composed of terrain, salt lakes, sand. The National Geographic Society considers the area of southern Peru to be part of the Atacama Desert. Peru borders it on the north and the Chilean Matorral ecoregion borders it on the south, to the east lies the less arid Central Andean dry puna ecoregion. The drier portion of this ecoregion is located south of the Loa River between the parallel Sierra Vicuña Mackenna and Cordillera Domeyko, to the north of the Loa lies the Pampa del Tamarugal. The Coastal Cliff of northern Chile west of the Chilean Coast Range is the topographic feature of the coast. The geomorphology of the Atacama Desert has been characterized as a low-relief bench similar to a giant uplifted terrace by Armijo and co-workers. The intermediate depression forms a series of basins in much of Atacama Desert south of latitude 19°30’ S. North of this latitude the intermediate depression drains into the Pacific Ocean. Although the almost total lack of precipitation is the most prominent characteristic of the Atacama Desert, in 2012, the altiplano winter brought floods to San Pedro de Atacama. On 25 March 2015, heavy rainfall affected the part of the Atacama desert. Resulting floods triggered mudflows that affected the cities of Copiapo, Tierra Amarilla, Chile, Chanaral, the Atacama Desert is commonly known as the driest non-polar place in the world, especially the surroundings of the abandoned Yungay town. The average rainfall is about 15 mm per year, although some locations, such as Arica and Iquique, moreover, some weather stations in the Atacama have never received rain. Periods of up to four years have been registered with no rainfall in the sector, delimited by the cities of Antofagasta, Calama and Copiapó. Evidence suggests that the Atacama may not have had any significant rainfall from 1570 to 1971, the Atacama Desert may be the oldest desert on earth, and has experienced extreme hyperaridity for at least 3 million years, making it the oldest continuously arid region on earth. The long history of aridity raises the possibility that supergene mineralisation, under the conditions, can form in arid environments. This desert is so arid, many mountains higher than 6,000 m are free of glaciers. Only the highest peaks have some permanent snow coverage, the southern part of the desert, between 25 and 27°S, may have been glacier-free throughout the Quaternary, though permafrost extends down to an altitude of 4,400 m and is continuous above 5,600 m
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Namib
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The Namib is a coastal desert in southern Africa. The name Namib is of Nama origin and means vast place, the Namibs northernmost portion, which extends 450 kilometres from the Angola-Namibia border, is known as Moçâmedes Desert, while its southern portion approaches the neighboring Kalahari Desert. From the Atlantic coast eastward, the Namib gradually ascends in elevation, annual precipitation ranges from 2 millimetres in the most arid regions to 200 millimetres at the escarpment, making the Namib the only true desert in southern Africa. Having endured arid or semi-arid conditions for roughly 55–80 million years, the desert geology consists of sand seas near the coast, while gravel plains and scattered mountain outcrops occur further inland. The sand dunes, some of which are 300 metres high, fogs that originate offshore from the collision of the cold Benguela Current and warm air from the Hadley Cell create a fog belt that frequently envelops parts of the desert. Coastal regions can experience more than 180 days of fog a year. While this has proved a hazard to ships—more than a thousand wrecks litter the Skeleton Coast—it is a vital source of moisture for desert life. Owing to its antiquity, the Namib may be home to endemic species than any other desert in the world. Most of the wildlife is arthropods and other small animals that live on little water. Near the coast, the ocean water is rich in fishery resources and supports populations of brown fur seals and shorebirds. Further inland, the Namib-Naukluft National Park, the largest game park in Africa, supports populations of African Bush Elephants, Mountain Zebras, and other large mammals. Although the outer Namib is largely barren of vegetation, lichens and succulents are found in areas, while grasses, shrubs. A few types of trees are able to survive the extremely arid climate. The Namib Desert is one of the 500 distinct physiographic provinces of the South African Platform physiographic division and it occupies an area of around 80,950 km², stretching from the[Usiab River to the town of Lüderitz and from the Atlantic Ocean to the Namib Escarpment. It is about 1,000 miles long north to south. To the south, the Namib borders on the South African Karoo semi-desert, southern Namib comprises a vast dune sea with some of the tallest and most spectacular dunes of the world, ranging in color from pink to vivid orange. In the Sossusvlei area, several dunes exceed 300 meters in height, the complexity and regularity of dune patterns in its dune sea have attracted the attention of geologists for decades, but it remains poorly understood. Moving north from Sossusvlei, the sand gradually gives way to a desert that extends all the way from Sossusvlei to the Swakop river
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Parasola plicatilis
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Parasola plicatilis is a small saprotrophic mushroom with a plicate cap. It is a widely distributed species in Europe and North America and this ink cap species is a decomposer which can be found in grassy areas, alone, scattered or in small groups. The fruiting bodies grow at night after rain, and will self decompose after spore dispersion is achieved, otherwise, they are quickly dried up in morning sunlight, or will eventually collapse beneath the weight of their caps. Media related to Parasola plicatilis at Wikimedia Commons
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Phytophthora infestans
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Phytophthora infestans is an oomycete that causes the serious potato disease known as late blight or potato blight. Late blight was a culprit in the 1840s European, the 1845 Irish. The organism can also infect tomatoes and some members of the Solanaceae. At first, the spots are gray-green and water-soaked, but they soon enlarge and turn brown and firm. The genus name Phytophthora comes from the Greek φυτό-, meaning plant, plus the Greek φθορά, meaning destruction, the species name infestans is the present participle of the Latin verb infestare, meaning attacking, destroying. The asexual life cycle of Phytophthora infestans is characterized by alternating phases of growth, sporulation, sporangia germination. There is also a cycle, which occurs when isolates of opposite mating type meet. Hormonal communication triggers the formation of the spores, called oospores. The different types of spores play major roles in the dissemination, sporangia are spread by wind or water and enable the movement of P. infestans between different host plants. The zoospores released from sporangia are biflagellated and chemotactic, allowing movement of P. infestans on water films found on leaves or soils. Both sporangia and zoospores are short-lived, in contrast to oospores which can persist in a form for many years. Under ideal conditions, the cycle can be completed on potato or tomato foliage in about five days. Sporangia develop on the leaves, spreading through the crop when temperatures are above 10 °C, rain can wash spores into the soil where they infect young tubers, and the spores can also travel long distances on the wind. The early stages of blight are easily missed, symptoms include the appearance of dark blotches on leaf tips and plant stems. White mould will appear under the leaves in humid conditions and the plant may quickly collapse. Infected tubers develop grey or dark patches that are reddish brown beneath the skin, seemingly healthy tubers may rot later when in store. P. infestans survives poorly in nature apart from its plant hosts, under most conditions, the hyphae and asexual sporangia can survive for only brief periods in plant debris or soil, and are generally killed off during frosts or very warm weather. The exceptions involve oospores, and hyphae present within tubers, the persistence of viable pathogen within tubers, such as those that are left in the ground after the previous years harvest or left in cull piles is a major problem in disease management
40.
Hebrew language
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Hebrew is a language native to Israel, spoken by over 9 million people worldwide, of whom over 5 million are in Israel. Historically, it is regarded as the language of the Israelites and their ancestors, the earliest examples of written Paleo-Hebrew date from the 10th century BCE. Hebrew belongs to the West Semitic branch of the Afroasiatic language family, Hebrew is the only living Canaanite language left, and the only truly successful example of a revived dead language. Hebrew had ceased to be a spoken language somewhere between 200 and 400 CE, declining since the aftermath of the Bar Kokhba revolt. Aramaic and to a lesser extent Greek were already in use as international languages, especially among elites and it survived into the medieval period as the language of Jewish liturgy, rabbinic literature, intra-Jewish commerce, and poetry. Then, in the 19th century, it was revived as a spoken and literary language, and, according to Ethnologue, had become, as of 1998, the language of 5 million people worldwide. After Israel, the United States has the second largest Hebrew-speaking population, with 220,000 fluent speakers, Modern Hebrew is one of the two official languages of the State of Israel, while premodern Hebrew is used for prayer or study in Jewish communities around the world today. Ancient Hebrew is also the tongue of the Samaritans, while modern Hebrew or Arabic is their vernacular. For this reason, Hebrew has been referred to by Jews as Leshon Hakodesh, the modern word Hebrew is derived from the word Ivri, one of several names for the Israelite people. It is traditionally understood to be a based on the name of Abrahams ancestor, Eber. This name is based upon the root ʕ-b-r meaning to cross over. Interpretations of the term ʕibrim link it to this verb, cross over, in the Bible, the Hebrew language is called Yәhudit because Judah was the surviving kingdom at the time of the quotation. In Isaiah 19,18 it is called the Language of Canaan, Hebrew belongs to the Canaanite group of languages. In turn, the Canaanite languages are a branch of the Northwest Semitic family of languages, according to Avraham ben-Yosef, Hebrew flourished as a spoken language in the Kingdoms of Israel and Judah during about 1200 to 586 BCE. Scholars debate the degree to which Hebrew was a vernacular in ancient times following the Babylonian exile. In July 2008 Israeli archaeologist Yossi Garfinkel discovered a ceramic shard at Khirbet Qeiyafa which he claimed may be the earliest Hebrew writing yet discovered, dating around 3000 years ago. The Gezer calendar also dates back to the 10th century BCE at the beginning of the Monarchic Period, classified as Archaic Biblical Hebrew, the calendar presents a list of seasons and related agricultural activities. The Gezer calendar is written in an old Semitic script, akin to the Phoenician one that through the Greeks, the Gezer calendar is written without any vowels, and it does not use consonants to imply vowels even in the places where later Hebrew spelling requires it
