Mammatus cloud
Mammatus, meaning "mammary cloud", is a cellular pattern of pouches hanging underneath the base of a cloud cumulonimbus rainclouds, although they may be attached to other classes of parent clouds. The name mammatus is derived from the Latin mamma. According to the WMO International Cloud Atlas, mamma is a cloud supplementary feature rather than a genus, species or variety of cloud, they are formed by cold air sinking down to form the pockets contrary to the puffs of clouds rising through the convection of warm air. These formations were first described in 1894 by William Clement Ley. Mammatus are most associated with anvil clouds and severe thunderstorms, they extend from the base of a cumulonimbus, but may be found under altocumulus, altostratus and cirrus clouds, as well as volcanic ash clouds. When occurring in cumulonimbus, mammatus are indicative of a strong storm or maybe a tornadic storm. Due to the intensely sheared environment in which mammatus form, aviators are cautioned to avoid cumulonimbus with mammatus as they indicate convectively induced turbulence.
Contrails may produce lobes but these are incorrectly termed as mammatus. Mammatus may be opaque or translucent; because mammatus occur as a grouping of lobes, the way they clump together can vary from an isolated cluster to a field of mammae that spread over hundreds of kilometers to being organized along a line, may be composed of unequal or similarly-sized lobes. The individual mammatus lobe average diameters of 1 -- lengths on average of 0.5 km. A lobe can last an average of 10 minutes, but a whole cluster of mamma can range from 15 minutes to a few hours, they are composed of ice, but can be a mixture of ice and liquid water or be composed of entirely liquid water. True to their ominous appearance, mammatus clouds are harbingers of a coming storm or other extreme weather system. Composed of ice, they can extend for hundreds of miles in each direction and individual formations can remain visibly static for ten to fifteen minutes at a time. While they may appear foreboding they are the messengers - appearing around, before or after severe weather.
The existence of many different types of mammatus clouds, each with distinct properties and occurring in distinct environments, has given rise to multiple hypotheses on their formation, which are relevant to other cloud forms. One environmental trend is shared by all of the formation mechanisms hypothesized for mammatus clouds: sharp gradients in temperature and momentum across the anvil cloud/sub-cloud air boundary, which influence interactions therein; the following are the proposed mechanisms, each described with its shortcomings: The anvil of a cumulonimbus cloud subsides as it spreads out from its source cloud. As air descends, it warms. However, the cloudy air will warm more than the sub-cloud, dry air; because of the differential warming, the cloud/sub-cloud layer destabilizes and convective overturning can occur, creating a lumpy cloud-base. The problems with this theory are that there are observations of mammatus lobes that do not support the presence of strong subsidence in the lobes, that it is difficult to separate the processes of hydrometeor fallout and cloud-base subsidence, thus rendering it unclear as to whether either process is occurring.
Cooling due to hydrometeor fallout is a second proposed formation mechanism. As hydrometeors fall into the dry sub-cloud air, the air containing the precipitation cools due to evaporation or sublimation. Being now cooler than the environmental air and unstable, they descend until in static equilibrium, at which point a restoring force curves the edges of the fallout back up, creating the lobed appearance. One problem with this theory is that observations show that cloud-base evaporation does not always produce mammatus; this mechanism could be responsible for the earliest stage of development, but other processes may come into play as the lobes are formed and mature. There may be destabilization at cloud base due to melting. If the cloud base exists near the freezing line the cooling in the immediate air caused by melting can lead to convective overturning, just as in the processes above. However, this strict temperature environment is not always present; the above processes relied on the destabilization of the sub-cloud layer due to adiabatic or latent heating effects.
Discounting the thermodynamical effects of hydrometeor fallout, another mechanism proposes that dynamics of the fallout alone are enough to create the lobes. Inhomogeneities in the masses of the hydrometeors along the cloud-base may cause inhomogeneous descent along the base. Frictional drag and associated eddy-like structures create the lobed appearance of the fallout; the main shortcoming of this theory is that vertical velocities in the lobes have been observed to be greater than the fall speeds of the hydrometeors within them. Another method, first proposed by Kerry Emanuel, is called cloud-base detrainment instability, which acts much like convective cloud-top entrainment. In CDI, cloudy air is mixed into the dry sub-cloud air rather than precipitating into it; the cloudy layer destabilizes due to evaporative cooling and mammatus are formed. Clouds undergo thermal reorganization due to radiative effects. There are a couple of ideas as to. One is that, b
Kelvin–Helmholtz instability
The Kelvin–Helmholtz instability can occur when there is velocity shear in a single continuous fluid, or where there is a velocity difference across the interface between two fluids. An example is wind blowing over water: The instability manifests in waves on the water surface. More clouds, the ocean, Saturn's bands, Jupiter's Red Spot, the sun's corona show this instability; the theory predicts the onset of instability and transition to turbulent flow in fluids of different densities moving at various speeds. Helmholtz studied the dynamics of two fluids of different densities when a small disturbance, such as a wave, was introduced at the boundary connecting the fluids. For some short enough wavelengths, if surface tension is ignored, two fluids in parallel motion with different velocities and densities yield an interface, unstable for all speeds. Surface tension stabilises the short wavelength instability however, theory predicts stability until a velocity threshold is reached; the theory, with surface tension included, broadly predicts the onset of wave formation in the important case of wind over water.
It was discovered that the fluid equations governing the linear dynamics of the system admit a parity-time symmetry, the Kelvin-Helmholtz instability occurs when and only when the parity-time symmetry breaks spontaneously. For a continuously varying distribution of density and velocity, the dynamics of the KH instability is described by the Taylor–Goldstein equation and its onset is given by the Richardson number R i; the layer is unstable for R i < 0.25. These effects are common in cloud layers; the study of this instability is applicable in plasma physics, for example in inertial confinement fusion and the plasma–beryllium interface. Numerically, the KH instability is simulated in a spatial approach. In the temporal approach, experimenters consider the flow in a periodic box "moving" at mean speed. In the spatial approach, experimenters simulate a lab experiment with natural inlet and outlet conditions. Rayleigh–Taylor instability Richtmyer–Meshkov instability Mushroom cloud Plateau–Rayleigh instability Kármán vortex street Taylor–Couette flow Fluid mechanics Fluid dynamics Lord Kelvin.
"Hydrokinetic solutions and observations". Philosophical Magazine. 42: 362–377. Hermann von Helmholtz. "Über discontinuierliche Flüssigkeits-Bewegungen ". Monatsberichte der Königlichen Preussische Akademie der Wissenschaften zu Berlin. 23: 215–228. Article describing discovery of K-H waves in deep ocean: Broad, William J.. "In Deep Sea, Waves With a Familiar Curl". New York Times. Retrieved April 23, 2010. Hwang, K.-J.. "The first in situ observation of Kelvin-Helmholtz waves at high-latitude magnetopause during dawnward interplanetary magnetic field conditions". J. Geophys. Res. 117: n/a. Bibcode:2012JGRA..117.8233H. Doi:10.1029/2011JA017256. Giant Tsunami-Shaped Clouds Roll Across Alabama Sky - Natalie Wolchover, Livescience via Yahoo.com Tsunami Cloud Hits Florida Coastline Vortex formation in free jet - YouTube video showing Kelvin Helmholtz waves on the edge of a free jet visualised in a scientific experiment. Wave clouds over Christchurch City Kelvin-Helmholtz clouds, in Barmouth, Gwynedd, on 18 February 2017
Pileus (meteorology)
A pileus called scarf cloud or cap cloud, is a small, lenticular cloud appearing above a cumulus or cumulonimbus cloud. Pileus clouds are short-lived, with the main cloud beneath them rising through convection to absorb them, they are formed by strong updraft at lower altitudes, acting upon moist air above, causing the air to cool to its dew point. As such, they are indicators of severe weather, a pileus found atop a cumulus cloud foreshadows transformation into a cumulonimbus cloud, as it indicates a strong updraft within the cloud. Pilei can form above mountains, ash clouds, pyrocumulus clouds from erupting volcanoes. Pilei form above some mushroom clouds of high-yield nuclear detonations. Sometimes several pileus clouds are observed above each other; the bright iridescent colors seen in pileus are sunlight diffracted in water vapor. Iridescent colors are strongest when the diffracting droplets are similar in size; the newly formed pileus droplet. When sheet of altostratus cloud is seen lower down and skirting a cumulonimbus cloud, it is classified as a velum cloud.
Pilei clouds indicate the parent cloud is growing has plenty of moisture, is unstable. This means the parent cloud could grow to become a cumulonimbus cloud and continue to grow into a cumulonimbus incus cloud. Atmospheric convection Lenticular cloud Helm Wind Video – Video of pileus clouds
Mountain
A mountain is a large landform that rises above the surrounding land in a limited area in the form of a peak. A mountain is steeper than a hill. Mountains are formed through tectonic forces or volcanism; these forces can locally raise the surface of the earth. Mountains erode through the action of rivers, weather conditions, glaciers. A few mountains are isolated summits. High elevations on mountains produce colder climates than at sea level; these colder climates affect the ecosystems of mountains: different elevations have different plants and animals. Because of the less hospitable terrain and climate, mountains tend to be used less for agriculture and more for resource extraction and recreation, such as mountain climbing; the highest mountain on Earth is Mount Everest in the Himalayas of Asia, whose summit is 8,850 m above mean sea level. The highest known mountain on any planet in the Solar System is Olympus Mons on Mars at 21,171 m. There is no universally accepted definition of a mountain.
Elevation, relief, steepness and continuity have been used as criteria for defining a mountain. In the Oxford English Dictionary a mountain is defined as "a natural elevation of the earth surface rising more or less abruptly from the surrounding level and attaining an altitude which to the adjacent elevation, is impressive or notable."Whether a landform is called a mountain may depend on local usage. Mount Scott outside Lawton, Oklahoma, USA, is only 251 m from its base to its highest point. Whittow's Dictionary of Physical Geography states "Some authorities regard eminences above 600 metres as mountains, those below being referred to as hills." In the United Kingdom and the Republic of Ireland, a mountain is defined as any summit at least 2,000 feet high, whilst the official UK government's definition of a mountain, for the purposes of access, is a summit of 600 metres or higher. In addition, some definitions include a topographical prominence requirement 100 or 500 feet. At one time the U.
S. Board on Geographic Names defined a mountain as being 1,000 feet or taller, but has abandoned the definition since the 1970s. Any similar landform lower. However, the United States Geological Survey concludes that these terms do not have technical definitions in the US; the UN Environmental Programme's definition of "mountainous environment" includes any of the following: Elevation of at least 2,500 m. Using these definitions, mountains cover 33% of Eurasia, 19% of South America, 24% of North America, 14% of Africa; as a whole, 24% of the Earth's land mass is mountainous. There are three main types of mountains: volcanic and block. All three types are formed from plate tectonics: when portions of the Earth's crust move and dive. Compressional forces, isostatic uplift and intrusion of igneous matter forces surface rock upward, creating a landform higher than the surrounding features; the height of the feature makes it either a hill or, if steeper, a mountain. Major mountains tend to occur in long linear arcs, indicating tectonic plate boundaries and activity.
Volcanoes are formed when a plate is pushed at a mid-ocean ridge or hotspot. At a depth of around 100 km, melting occurs in rock above the slab, forms magma that reaches the surface; when the magma reaches the surface, it builds a volcanic mountain, such as a shield volcano or a stratovolcano. Examples of volcanoes include Mount Pinatubo in the Philippines; the magma does not have to reach the surface in order to create a mountain: magma that solidifies below ground can still form dome mountains, such as Navajo Mountain in the US. Fold mountains occur when two plates collide: shortening occurs along thrust faults and the crust is overthickened. Since the less dense continental crust "floats" on the denser mantle rocks beneath, the weight of any crustal material forced upward to form hills, plateaus or mountains must be balanced by the buoyancy force of a much greater volume forced downward into the mantle, thus the continental crust is much thicker under mountains, compared to lower lying areas.
Rock can fold either asymmetrically. The upfolds are anticlines and the downfolds are synclines: in asymmetric folding there may be recumbent and overturned folds; the Balkan Mountains and the Jura Mountains are examples of fold mountains. Block mountains are caused by faults in the crust: a plane; when rocks on one side of a fault rise relative to the other, it can form a mountain. The uplifted blocks are block horsts; the intervening dropped blocks are termed graben: these can be small or form extensive rift valley systems. This form of landscape can be seen in East Africa, the Vosges, the Basin and Range Province of Western North America and the Rhine valley; these areas occur when the regional stress is extensional and the crust is thinned. During and following uplift, mountains are subjected to the agents of erosion which wear the uplifted area down. Erosion causes the surface of mountains to be younger than the rocks that form the mountains themselves. Glacial processes produce characteristic landforms, such as pyramidal peaks, knife-edge arêtes, bowl-shaped cirques that can contai
Cumulus mediocris cloud
Cumulus mediocris is a low to middle level cloud with some vertical extent of the genus cumulus, larger in vertical development than Cumulus humilis. It may exhibit small protuberances from the top and may show the cauliflower form characteristic of cumulus clouds. Cumulus mediocris clouds do not produce precipitation of more than light intensity, but can further advance into clouds such as Cumulus congestus or Cumulonimbus, which do produce precipitation. Cumulus mediocris is classified as a low cloud and is coded CL2 by the World Meteorological Organization. Cumulus mediocris is brilliantly white when sunlit, is dark underneath. A single pattern-based variety, Cumulus radiatus, is sometime seen when the individual clouds are arranged into parallel rows; the resulting formations are aligned nearly parallel to the wind. Cumulus mediocris may have precipitation-based features like virga, may form Cumulus praecipitato clouds; the pannus supplementary feature is sometimes seen with precipitating Cumulus mediocris, but in this case the CL7 reporting code used with to identify pannus is superseded by CL2, since there is significant vertical development.
Pileus, velum and tuba features are occasionally seen with cumulus mediocris. Cumulus mediocris may form as a result of a partial transformation of stratocumulus; this genus and species type may be the result of a complete transformation of stratocumulus or stratus. These clouds are common in the advance of a cold front or in unstable atmospheric conditions such as an area of low pressure, they can grow into larger Cumulus congestus which could bring rain, winds and in worse cases and lightning. If these clouds are present in the morning or early afternoon they show a significant instability in the atmosphere leading to storms in the day; these clouds occur. Like any cumulus cloud, this cloud requires convection before developing; this occurs when pockets of air around them begin to rise. As the air rises, it condenses forming a Cumulus humilis cloud as it continues to rise, a Cumulus mediocris. Atmospheric convection Cumulus congestus
Fractus cloud
Fractus clouds are small, ragged cloud fragments that are found under an ambient cloud base. They form or have broken off from a larger cloud, are sheared by strong winds, giving them a jagged, shredded appearance. Fractus have irregular patterns, they change often forming and dissipating rapidly. They do not have defined bases. Sometimes they are persistent and form near the surface. Common kinds include cloud tags. Fractus are accessory clouds, named for the type of cloud from; the two principal forms are cumulus stratus fractus. Fractus clouds may develop into cumulus. Stratus fractus is distinguishable from cumulus fractus by its smaller vertical extent, darker color, by the greater dispersion of its particles. Cumulus fractus clouds look like ragged cumulus clouds, they may originate from dissipated cumulus clouds, appearing in this case as white ragged clouds located at significant distances from each other. Cumulus fractus in particular form on the leading and trailing edges of summer storms in warm and humid conditions.
Observing fractus gives an indication of wind movements under the parent cloud. Masses of multiple fractus clouds, located under a main cloud, are called pannus. Fractonimbus are a form of stratus fractus, developing under precipitation clouds due to turbulent air movement, they are ragged in appearance. Fractonimbus exist only under precipitation clouds, don't produce precipitation themselves. Fractonimbus may merge with overlying nimbostratus clouds. In rainstorms, scud form in the updraft area where the air has been cooled by precipitation from the downdraft, thus condensation occurs below the ambient cloud deck. If scud are rising and moving towards the main updraft, sometimes marked by a rain-free base or wall cloud the thunderstorm is still developing from rising scud. In addition to forming in inflow, fractus form in outflow. Scud are common on the leading edge of a thunderstorm where warm, moist air is lifted by the gust front. Scud are found under shelf clouds. List of cloud types
Cloud
In meteorology, a cloud is an aerosol consisting of a visible mass of minute liquid droplets, frozen crystals, or other particles suspended in the atmosphere of a planetary body or similar space. Water or various other chemicals may compose the crystals. On Earth, clouds are formed as a result of saturation of the air when it is cooled to its dew point, or when it gains sufficient moisture from an adjacent source to raise the dew point to the ambient temperature, they are seen in the Earth's homosphere. Nephology is the science of clouds, undertaken in the cloud physics branch of meteorology. There are two methods of naming clouds in their respective layers of the atmosphere. Cloud types in the troposphere, the atmospheric layer closest to Earth's surface, have Latin names due to the universal adaptation of Luke Howard's nomenclature. Formally proposed in 1802, it became the basis of a modern international system that divides clouds into five physical forms that appear in any or all of three altitude levels.
These physical types, in approximate ascending order of convective activity, include stratiform sheets, cirriform wisps and patches, stratocumuliform layers, cumuliform heaps, large cumulonimbiform heaps that show complex structure. The physical forms are divided by altitude level into ten basic genus-types; the Latin names for applicable high-level genera carry a cirro- prefix, an alto- prefix is added to the names of the mid-level genus-types. Most of the genera can be further subdivided into varieties. Low stratiform clouds that extend down to the Earth's surface are given the common names fog and mist, but have no Latin names. Several clouds that form higher up in the stratosphere and mesosphere have common names for their main types, they are seen infrequently in the polar regions of Earth. Clouds have been observed in the atmospheres of other planets and moons in the Solar System and beyond. However, due to their different temperature characteristics, they are composed of other substances such as methane and sulfuric acid as well as water.
Taken as a whole, homospheric clouds can be cross-classified by form and level to derive the ten tropospheric genera, the fog and mist that forms at surface level, several additional major types above the troposphere. The cumulus genus includes three species. Clouds with sufficient vertical extent to occupy more than one altitude level are classified as low- or mid-level according to the altitude range at which each forms; however they are more informally classified as multi-level or vertical. The origin of the term cloud can be found in the old English clud or clod, meaning a hill or a mass of rock. Around the beginning of the 13th century, the word came to be used as a metaphor for rain clouds, because of the similarity in appearance between a mass of rock and cumulus heap cloud. Over time, the metaphoric usage of the word supplanted the old English weolcan, the literal term for clouds in general. Ancient cloud studies were not made in isolation, but were observed in combination with other weather elements and other natural sciences.
In about 340 BC the Greek philosopher Aristotle wrote Meteorologica, a work which represented the sum of knowledge of the time about natural science, including weather and climate. For the first time and the clouds from which precipitation fell were called meteors, which originate from the Greek word meteoros, meaning'high in the sky'. From that word came the modern term meteorology, the study of clouds and weather. Meteorologica was based on intuition and simple observation, but not on what is now considered the scientific method, it was the first known work that attempted to treat a broad range of meteorological topics. After centuries of speculative theories about the formation and behavior of clouds, the first scientific studies were undertaken by Luke Howard in England and Jean-Baptiste Lamarck in France. Howard was a methodical observer with a strong grounding in the Latin language and used his background to classify the various tropospheric cloud types during 1802, he believed. Lamarck had worked independently on cloud classification the same year and had come up with a different naming scheme that failed to make an impression in his home country of France because it used unusual French names for cloud types.
His system of nomenclature included twelve categories of clouds, with such names as hazy clouds, dappled clouds and broom-like clouds. By contrast, Howard used universally accepted Latin, which caught on after it was published in 1803; as a sign of the popularity of the naming scheme, the German dramatist and poet Johann Wolfgang von Goethe composed four poems about clouds, dedicating them to Howard. An elaboration of Howard's system was formally adopted by the International Meteorological Conference in 1891; this system covered only the tropospheric cloud types, but the discovery of clouds above the troposphere during the late 19th century led to the creation separate classification schemes for these high clouds. Terrestrial clouds can be found throughout most of the homosphere, which includes the troposphere and mesosphere. Within these layers of the atmosphere, air can become saturated as a result of being cooled to its dew point or by having moisture added from an adjacent source. In the latter case, saturation occurs when the dew po
