Meteorology is a branch of the atmospheric sciences which includes atmospheric chemistry and atmospheric physics, with a major focus on weather forecasting. The study of meteorology dates back millennia, though significant progress in meteorology did not occur until the 18th century; the 19th century saw modest progress in the field after weather observation networks were formed across broad regions. Prior attempts at prediction of weather depended on historical data, it was not until after the elucidation of the laws of physics and more the development of the computer, allowing for the automated solution of a great many equations that model the weather, in the latter half of the 20th century that significant breakthroughs in weather forecasting were achieved. An important domain of weather forecasting is marine weather forecasting as it relates to maritime and coastal safety, in which weather effects include atmospheric interactions with large bodies of water. Meteorological phenomena are observable weather events that are explained by the science of meteorology.
Meteorological phenomena are described and quantified by the variables of Earth's atmosphere: temperature, air pressure, water vapour, mass flow, the variations and interactions of those variables, how they change over time. Different spatial scales are used to describe and predict weather on local and global levels. Meteorology, atmospheric physics, atmospheric chemistry are sub-disciplines of the atmospheric sciences. Meteorology and hydrology compose the interdisciplinary field of hydrometeorology; the interactions between Earth's atmosphere and its oceans are part of a coupled ocean-atmosphere system. Meteorology has application in many diverse fields such as the military, energy production, transport and construction; the word meteorology is from the Ancient Greek μετέωρος metéōros and -λογία -logia, meaning "the study of things high in the air". The ability to predict rains and floods based on annual cycles was evidently used by humans at least from the time of agricultural settlement if not earlier.
Early approaches to predicting weather were practiced by priests. Cuneiform inscriptions on Babylonian tablets included associations between rain; the Chaldeans differentiated 46 ° halos. Ancient Indian Upanishads contain mentions of seasons; the Samaveda mentions sacrifices to be performed. Varāhamihira's classical work Brihatsamhita, written about 500 AD, provides evidence of weather observation. In 350 BC, Aristotle wrote Meteorology. Aristotle is considered the founder of meteorology. One of the most impressive achievements described in the Meteorology is the description of what is now known as the hydrologic cycle; the book De Mundo noted If the flashing body is set on fire and rushes violently to the Earth it is called a thunderbolt. They are all called ` swooping bolts'. Lightning is sometimes smoky, is called'smoldering lightning". At other times, it travels in crooked lines, is called forked lightning; when it swoops down upon some object it is called'swooping lightning'. The Greek scientist Theophrastus compiled a book on weather forecasting, called the Book of Signs.
The work of Theophrastus remained a dominant influence in the study of weather and in weather forecasting for nearly 2,000 years. In 25 AD, Pomponius Mela, a geographer for the Roman Empire, formalized the climatic zone system. According to Toufic Fahd, around the 9th century, Al-Dinawari wrote the Kitab al-Nabat, in which he deals with the application of meteorology to agriculture during the Muslim Agricultural Revolution, he describes the meteorological character of the sky, the planets and constellations, the sun and moon, the lunar phases indicating seasons and rain, the anwa, atmospheric phenomena such as winds, lightning, floods, rivers, lakes. Early attempts at predicting weather were related to prophecy and divining, were sometimes based on astrological ideas. Admiral FitzRoy tried to separate scientific approaches from prophetic ones. Ptolemy wrote on the atmospheric refraction of light in the context of astronomical observations. In 1021, Alhazen showed that atmospheric refraction is responsible for twilight.
St. Albert the Great was the first to propose that each drop of falling rain had the form of a small sphere, that this form meant that the rainbow was produced by light interacting with each raindrop. Roger Bacon was the first to calculate the angular size of the rainbow, he stated. In the late 13th century and early 14th century, Kamāl al-Dīn al-Fārisī and Theodoric of Freiberg were the first to give the correct explanations for the primary rainbow phenomenon. Theoderic went further and explained the secondary rainbow. In 1716, Edmund Halley suggested that aurorae are caused by "magnetic effluvia" moving along the Earth's magnetic field lines. In 1441, King Sejong's son, Prince Munjong of Korea, invented the first standardized rain gauge; these were sent throughout the Joseon dynasty of Korea as an official tool to assess land taxes based
A tropical cyclone is a rotating storm system characterized by a low-pressure center, a closed low-level atmospheric circulation, strong winds, a spiral arrangement of thunderstorms that produce heavy rain. Depending on its location and strength, a tropical cyclone is referred to by different names, including hurricane, tropical storm, cyclonic storm, tropical depression, cyclone. A hurricane is a tropical cyclone that occurs in the Atlantic Ocean and northeastern Pacific Ocean, a typhoon occurs in the northwestern Pacific Ocean. "Cyclone" refers to their winds moving in a circle, whirling round their central clear eye, with their winds blowing counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. The opposite direction of circulation is due to the Coriolis effect. Tropical cyclones form over large bodies of warm water, they derive their energy through the evaporation of water from the ocean surface, which recondenses into clouds and rain when moist air rises and cools to saturation.
This energy source differs from that of mid-latitude cyclonic storms, such as nor'easters and European windstorms, which are fueled by horizontal temperature contrasts. Tropical cyclones are between 100 and 2,000 km in diameter; the strong rotating winds of a tropical cyclone are a result of the conservation of angular momentum imparted by the Earth's rotation as air flows inwards toward the axis of rotation. As a result, they form within 5° of the equator. Tropical cyclones are unknown in the South Atlantic due to a strong wind shear and a weak Intertropical Convergence Zone; the African easterly jet and areas of atmospheric instability which give rise to cyclones in the Atlantic Ocean and Caribbean Sea, along with the Asian monsoon and Western Pacific Warm Pool, are features of the Northern Hemisphere and Australia. Coastal regions are vulnerable to the impact of a tropical cyclone, compared to inland regions; the primary energy source for these storms is warm ocean waters, therefore these forms are strongest when over or near water, weaken quite over land.
Coastal damage may be caused by strong winds and rain, high waves, storm surges, the potential of spawning tornadoes. Tropical cyclones draw in air from a large area—which can be a vast area for the most severe cyclones—and concentrate the precipitation of the water content in that air into a much smaller area; this continual replacement of moisture-bearing air by new moisture-bearing air after its moisture has fallen as rain, which may cause heavy rain and river flooding up to 40 kilometres from the coastline, far beyond the amount of water that the local atmosphere holds at any one time. Though their effects on human populations are devastating, tropical cyclones can relieve drought conditions, they carry heat energy away from the tropics and transport it toward temperate latitudes, which may play an important role in modulating regional and global climate. Tropical cyclones are areas of low pressure in the troposphere, with the largest pressure perturbations occurring at low altitudes near the surface.
On Earth, the pressures recorded at the centers of tropical cyclones are among the lowest observed at sea level. The environment near the center of tropical cyclones is warmer than the surroundings at all altitudes, thus they are characterized as "warm core" systems; the near-surface wind field of a tropical cyclone is characterized by air rotating around a center of circulation while flowing radially inwards. At the outer edge of the storm, air may be nearly calm; as air flows radially inward, it begins to rotate cyclonically in order to conserve angular momentum. At an inner radius, air begins to ascend to the top of the troposphere; this radius is coincident with the inner radius of the eyewall, has the strongest near-surface winds of the storm. Once aloft, air flows away from the storm's center; the mentioned processes result in a wind field, nearly axisymmetric: Wind speeds are low at the center, increase moving outwards to the radius of maximum winds, decay more with radius to large radii.
However, the wind field exhibits additional spatial and temporal variability due to the effects of localized processes, such as thunderstorm activity and horizontal flow instabilities. In the vertical direction, winds are strongest near the surface and decay with height within the troposphere. At the center of a mature tropical cyclone, air sinks rather than rises. For a sufficiently strong storm, air may sink over a layer deep enough to suppress cloud formation, thereby creating a clear "eye". Weather in the eye is calm and free of clouds, although the sea may be violent; the eye is circular in shape, is 30–65 km in diameter, though eyes as small as 3 km and as large as 370 km have been observed. The cloudy outer edge of the eye is called the "eyewall"; the eyewall expands outward with height, resembling an arena foo
This article is about the image transmission mode. For the radio station, see Radiofax. Radiofax known as weatherfax and HF fax, is an analogue mode for transmitting monochrome images, it was the predecessor to slow-scan television. Prior to the advent of the commercial telephone line "fax" machine, it was known, more traditionally, by the term "radiofacsimile"; the cover of the regular NOAA publication on frequencies and schedules states "Worldwide Marine Radiofacsimile Broadcast Schedules". Facsimile machines were used in the 1950s to transmit weather charts across the United States via land-lines first and internationally via HF radio. Radio transmission of weather charts provides an enormous amount of flexibility to marine and aviation users for they now have the latest weather information and forecasts at their fingertips to use in the planning of voyages. Radiofax relies on facsimile technology where printed information is scanned line by line and encoded into an electrical signal which can be transmitted via physical line or radio waves to remote locations.
Since the amount of information transmitted per unit time is directly proportional to the bandwidth available the speed at which a weather chart can be transmitted will vary depending on the quality of the media used for transmission. Today radiofax data is available via FTP downloads from sites in the Internet such as the ones hosted by the National Oceanic and Atmospheric Administration. Radiofax transmissions are broadcast by NOAA from multiple sites in the country at regular daily schedules. Radio weatherfax transmissions are useful to shipping, where there are limited facilities for accessing the Internet; the term weatherfax was coined after the technology that allows the transmission and reception of weather charts from a transmission site to a remote site. Radiofax is transmitted in single sideband, a refinement of amplitude modulation; the signal shifts down a given amount to designate white or black pixels. A deviation less than that for a black pixel is taken to be a shade of grey.
With correct tuning, the signal shares some characteristics with SSTV, with black at 1500 Hz and peak white at 2300 Hz. 120 lines per minute are sent. A value known as the index of cooperation must be known to decode a radio fax transmission - this governs the image resolution, derives from early radio fax machines which used drum readers, is the product of the total line length and the number of lines per unit length, divided by π; the IOC is 576. APT format permits unattended monitoring of services, it is employed by most terrestrial weather facsimile stations as well as geostationary weather satellites. The start tone triggers the receiving system, it was meant to allow enough time for the drum of mechanical systems to get up to speed. It consists of rapid modulation of the video carrier; the phasing signal, consisting of a periodic pulse, synchronizes the receiver so that the image will be centered on the paper. The stop tone, optionally followed by black, marks the end of the transmission. Today, radiofax is used worldwide for the dissemination of weather charts, satellite weather images, forecasts to ships at sea.
The oceans are covered by coastal stations in various countries. In the United States, fax weather products are prepared by a number of offices and agencies within the National Weather Service of the National Oceanic and Atmospheric Administration. Tropical and hurricane products come from the Tropical Analysis and Forecast Branch, part of the Tropical Prediction Center/National Hurricane Center, they are broadcast over US Coast Guard communication stations NMG, in New Orleans, LA, NMC, the Pacific master station on Point Reyes, CA. After Hurricane Katrina damaged NMG, the Boston Coast Guard station NMF added a limited schedule of tropical warning charts. NMG is back at full capability. All other products come from the Ocean Prediction Center of the NWS, in cooperation with several other offices depending on the region and nature of information; these use NMG, NMC, NMF, plus Coast Guard station NOJ in Kodiak and Department of Defense station KVM70 in Hawaii. Since the RMS Titanic dramatized the dangers of icebergs in the North Atlantic, an International Ice Patrol has originated weather data, its charts are broadcast by the Boston station during the prime iceberg season of February through September, using the callsign NIK.
A major producer of Canadian radiofax is the Canadian Forces METOC in Halifax, NS, using the communication station CFH. Charts are sent on the hour the station switches to radioteletype for the rest of the period. CBV, Playa Ancha Radio in Valparaiso, Chile broadcasts a daily schedule of Armada de Chile weather fax for the southeastern Pacific, all the way to the Antarctic. In the Pacific, Japan has two stations, as does the Bureau of Meteorology in Australia. Most European countries have stations. Kyodo News is the only remaining news agency, it broadcasts complete newspapers in Japanese and English at 60 lines per minute instead of the more normal 120 because of the greate
National Hurricane Center
The National Hurricane Center is the division of the United States' National Weather Service responsible for tracking and predicting tropical weather systems between the Prime Meridian and the 140th meridian west poleward to the 30th parallel north in the northeast Pacific Ocean and the 31st parallel north in the northern Atlantic Ocean. The agency, co-located with the Miami branch of the National Weather Service, is situated on the campus of Florida International University in University Park, Florida; the NHC's Tropical Analysis and Forecast Branch issues marine forecasts, in the form of graphics and high seas forecasts year round, with the Ocean Prediction Center having backup responsibility for this unit. The Technology and Science Branch provides technical support for the center, which includes new infusions of technology from abroad; the Chief, Aerial Reconnaissance Coordination, All Hurricanes unit tasks planes, for research and operational purposes, to tropical cyclones during the Atlantic hurricane season and significant weather events, including snow storms, during winter and spring.
Research to improve operational forecasts is done through the Hurricane Forecast Improvement Project and Joint Hurricane Test Bed initiatives. During the Atlantic and northeast Pacific hurricane seasons, the Hurricane Specialists Unit issues routine tropical weather outlooks for the northeast Pacific and northern Atlantic oceans; when tropical storm or hurricane conditions are expected within 48 hours, the center issues watches and warnings via the news media and National Oceanic and Atmospheric Administration Weather Radio. Although the NHC is an agency of the United States, the World Meteorological Organization has designated it as the Regional Specialized Meteorological Center for the North Atlantic and eastern Pacific, making it the clearinghouse for tropical cyclone forecasts and observations occurring in these areas. If the NHC loses power or becomes incapacitated, the Central Pacific Hurricane Center backs tropical cyclone advisories and tropical weather outlooks for the northeast Pacific Ocean while the Weather Prediction Center backs up tropical cyclone advisories and tropical weather outlooks for the North Atlantic Ocean.
The first hurricane warning service was set up in the 1870s from Cuba with the work of Father Benito Viñes. After his death, hurricane warning services were assumed by the United States Signal Corps and United States Weather Bureau over the next decade, first based in Jamaica in 1898 and Cuba in 1899 before shifting to Washington, D. C. in 1902. The central office in Washington, which evolved into the National Meteorological Center and Weather Prediction Center, assumed hurricane warning/advisory responsibility at that time; this responsibility passed to regional hurricane offices in 1935, the concept of the Atlantic hurricane season was established to keep a vigilant lookout for tropical cyclones during certain times of the year. Hurricane advisories issued; the Jacksonville hurricane warning office moved to Miami, Florida, in 1943. Tropical cyclone naming began for Atlantic tropical cyclones using the Joint Army/Navy Phonetic Alphabet by 1947. In 1950, the Miami Hurricane Warning Office began to prepare the annual hurricane season summary articles.
In the 1953 Atlantic season, the United States Weather Bureau began naming storms which reach tropical storm intensity with human names. The National Hurricane Research Project, begun in the 1950s, used aircraft to study tropical cyclones and carry out experiments on mature hurricanes through its Project Stormfury. On July 1, 1956, a National Hurricane Information Center was established in Miami, which became a warehouse for all hurricane-related information from one United States Weather Bureau office; the Miami Hurricane Warning Office moved from Lindsey Hopkins Hotel to the Aviation Building 4 miles to the northwest on July 1, 1958. Forecasts within the hurricane advisories were issued one day into the future in 1954 before being extended to two days into the future in 1961, three days into the future in 1964, five days into the future in 2001; the Miami HWO moved to the campus of the University of Miami in 1964, was referred to as the NHC in 1965. The Miami HWO tropical cyclone reports were done and took on their modern format in 1964.
Beginning in 1973, the National Meteorological Center duties gained advisory responsibility for tracking and publicizing inland tropical depressions. The World Meteorological Organization assumed control of the Atlantic hurricane naming list in 1977. In 1978, the NHC's offices moved off the campus of the University of Miami across U. S. Highway 1 to the IRE Financial Building. Male names were added into the hurricane list beginning in the 1979 season; the hurricane warning offices remained active past 1983. In 1984, the NHC was separated from the Miami Weather Service Forecast Office, which meant the meteorologist in charge at Miami was no longer in a supervisory position over the hurricane center director. By 1988, the NHC gained responsibility for eastern Pacific tropical cyclones as the former Eastern Pacific Hurricane Center in San Francisco was decommissioned. In 1992, Hurricane Andrew blew the WSR-57 weather radar and the anemometer off the roof of NHC's/the Miami State Weather Forecast offices.
The radar was replaced with a WSR-88D NEXRAD system in April 1993 installed near Metro Zoo, near where Hurricane Andrew made landfall. In 1995, the NHC moved into a new hurricane-resistant facility on the campus of Florida International University, capable of wi
Weather forecasting is the application of science and technology to predict the conditions of the atmosphere for a given location and time. People have attempted to predict the weather informally for millennia and formally since the 19th century. Weather forecasts are made by collecting quantitative data about the current state of the atmosphere at a given place and using meteorology to project how the atmosphere will change. Once calculated by hand based upon changes in barometric pressure, current weather conditions, sky condition or cloud cover, weather forecasting now relies on computer-based models that take many atmospheric factors into account. Human input is still required to pick the best possible forecast model to base the forecast upon, which involves pattern recognition skills, knowledge of model performance, knowledge of model biases; the inaccuracy of forecasting is due to the chaotic nature of the atmosphere, the massive computational power required to solve the equations that describe the atmosphere, the error involved in measuring the initial conditions, an incomplete understanding of atmospheric processes.
Hence, forecasts become less accurate as the difference between current time and the time for which the forecast is being made increases. The use of ensembles and model consensus help narrow the error and pick the most outcome. There are a variety of end uses to weather forecasts. Weather warnings are important forecasts because they are used to protect property. Forecasts based on temperature and precipitation are important to agriculture, therefore to traders within commodity markets. Temperature forecasts are used by utility companies to estimate demand over coming days. On an everyday basis, people use weather forecasts to determine. Since outdoor activities are curtailed by heavy rain and wind chill, forecasts can be used to plan activities around these events, to plan ahead and survive them. In 2009, the US spent $5.1 billion on weather forecasting. For millennia people have tried to forecast the weather. In 650 BC, the Babylonians predicted the weather from cloud patterns as well as astrology.
In about 350 BC, Aristotle described weather patterns in Meteorologica. Theophrastus compiled a book on weather forecasting, called the Book of Signs. Chinese weather prediction lore extends at least as far back as 300 BC, around the same time ancient Indian astronomers developed weather-prediction methods. In New Testament times, Christ himself referred to deciphering and understanding local weather patterns, by saying, "When evening comes, you say,'It will be fair weather, for the sky is red', in the morning,'Today it will be stormy, for the sky is red and overcast.' You know how to interpret the appearance of the sky, but you cannot interpret the signs of the times."In 904 AD, Ibn Wahshiyya's Nabatean Agriculture, translated into Arabic from an earlier Aramaic work, discussed the weather forecasting of atmospheric changes and signs from the planetary astral alterations. Ancient weather forecasting methods relied on observed patterns of events termed pattern recognition. For example, it might be observed that if the sunset was red, the following day brought fair weather.
This experience accumulated over the generations to produce weather lore. However, not all of these predictions prove reliable, many of them have since been found not to stand up to rigorous statistical testing, it was not until the invention of the electric telegraph in 1835 that the modern age of weather forecasting began. Before that, the fastest that distant weather reports could travel was around 100 miles per day, but was more 40–75 miles per day. By the late 1840s, the telegraph allowed reports of weather conditions from a wide area to be received instantaneously, allowing forecasts to be made from knowledge of weather conditions further upwind; the two men credited with the birth of forecasting as a science were an officer of the Royal Navy Francis Beaufort and his protégé Robert FitzRoy. Both were influential men in British naval and governmental circles, though ridiculed in the press at the time, their work gained scientific credence, was accepted by the Royal Navy, formed the basis for all of today's weather forecasting knowledge.
Beaufort developed the Wind Force Scale and Weather Notation coding, which he was to use in his journals for the remainder of his life. He promoted the development of reliable tide tables around British shores, with his friend William Whewell, expanded weather record-keeping at 200 British Coast guard stations. Robert FitzRoy was appointed in 1854 as chief of a new department within the Board of Trade to deal with the collection of weather data at sea as a service to mariners; this was the forerunner of the modern Meteorological Office. All ship captains were tasked with collating data on the weather and computing it, with the use of tested instruments that were loaned for this purpose. A storm in 1859 that caused the loss of the Royal Charter inspired FitzRoy to develop charts to allow predictions to be made, which he called "forecasting the weather", thus coining the term "weather forecast". Fifteen land stations were established to use the telegraph to transmit to him daily reports of weather at set times leading to the first gale warning service.
His warning service for shipping was initiated in February 1861, with the use of telegraph communications. The first daily weather forecasts were published in The Times in 1861. In the following year a system was introduced of hoistin
Radio broadcasting is transmission by radio waves intended to reach a wide audience. Stations can be linked in radio networks to broadcast a common radio format, either in broadcast syndication or simulcast or both; the signal types can be digital audio. The earliest radio stations did not carry audio. For audio broadcasts to be possible, electronic detection and amplification devices had to be incorporated; the thermionic valve was invented in 1904 by the English physicist John Ambrose Fleming. He developed a device he called an "oscillation valve"; the heated filament, or cathode, was capable of thermionic emission of electrons that would flow to the plate when it was at a higher voltage. Electrons, could not pass in the reverse direction because the plate was not heated and thus not capable of thermionic emission of electrons. Known as the Fleming valve, it could be used as a rectifier of alternating current and as a radio wave detector; this improved the crystal set which rectified the radio signal using an early solid-state diode based on a crystal and a so-called cat's whisker.
However, what was still required was an amplifier. The triode was patented on March 4, 1906, by the Austrian Robert von Lieben independent from that, on October 25, 1906, Lee De Forest patented his three-element Audion, it wasn't put to practical use until 1912 when its amplifying ability became recognized by researchers. By about 1920, valve technology had matured to the point where radio broadcasting was becoming viable. However, an early audio transmission that could be termed a broadcast may have occurred on Christmas Eve in 1906 by Reginald Fessenden, although this is disputed. While many early experimenters attempted to create systems similar to radiotelephone devices by which only two parties were meant to communicate, there were others who intended to transmit to larger audiences. Charles Herrold started broadcasting in California in 1909 and was carrying audio by the next year.. In The Hague, the Netherlands, PCGG started broadcasting on November 6, 1919, making it, arguably the first commercial broadcasting station.
In 1916, Frank Conrad, an electrical engineer employed at the Westinghouse Electric Corporation, began broadcasting from his Wilkinsburg, Pennsylvania garage with the call letters 8XK. The station was moved to the top of the Westinghouse factory building in East Pittsburgh, Pennsylvania. Westinghouse relaunched the station as KDKA on November 2, 1920, as the first commercially licensed radio station in America; the commercial broadcasting designation came from the type of broadcast license. The first licensed broadcast in the United States came from KDKA itself: the results of the Harding/Cox Presidential Election; the Montreal station that became CFCF began broadcast programming on May 20, 1920, the Detroit station that became WWJ began program broadcasts beginning on August 20, 1920, although neither held a license at the time. In 1920, wireless broadcasts for entertainment began in the UK from the Marconi Research Centre 2MT at Writtle near Chelmsford, England. A famous broadcast from Marconi's New Street Works factory in Chelmsford was made by the famous soprano Dame Nellie Melba on 15 June 1920, where she sang two arias and her famous trill.
She was the first artist of international renown to participate in direct radio broadcasts. The 2MT station began to broadcast regular entertainment in 1922; the BBC was amalgamated in 1922 and received a Royal Charter in 1926, making it the first national broadcaster in the world, followed by Czech Radio and other European broadcasters in 1923. Radio Argentina began scheduled transmissions from the Teatro Coliseo in Buenos Aires on August 27, 1920, making its own priority claim; the station got its license on November 19, 1923. The delay was due to the lack of official Argentine licensing procedures before that date; this station continued regular broadcasting of entertainment and cultural fare for several decades. Radio in education soon followed and colleges across the U. S. began adding radio broadcasting courses to their curricula. Curry College in Milton, Massachusetts introduced one of the first broadcasting majors in 1932 when the college teamed up with WLOE in Boston to have students broadcast programs.
Broadcasting service is – according to Article 1.38 of the International Telecommunication Union´s Radio Regulations – defined as «A radiocommunication service in which the transmission are intended for direct reception by the general public. This service may include sound transmissions, television transmissions or other types of transmission.» Definitions identical to those contained in the Annexes to the Constitution and Convention of the International Telecommunication Union are marked "" or "" respectively. A radio broadcasting station is associated with wireless transmission, though in practice broadcasting transmission take place using both wires and radio waves; the point of this is that anyone with the appropriate receiving technology can receive the broadcast. In line to ITU Radio Regulations each broadcasting station shall be classified by the service in which it operates permanently or temporarily. Broadcasting by radio takes several forms; these include FM stations. There are several subtypes, namely commercial broadcasting, non-commercial educational public broadcasting and non-profit varieties as well as community radio, student-run campus radio stations, and
Climatology or climate science is the scientific study of climate, scientifically defined as weather conditions averaged over a period of time. This modern field of study is regarded as a branch of the atmospheric sciences and a subfield of physical geography, one of the Earth sciences. Climatology now includes aspects of biogeochemistry. Basic knowledge of climate can be used within shorter term weather forecasting using analog techniques such as the El Niño–Southern Oscillation, the Madden–Julian oscillation, the North Atlantic oscillation, the Northern Annular Mode, known as the Arctic oscillation, the Northern Pacific Index, the Pacific decadal oscillation, the Interdecadal Pacific Oscillation. Climate models are used for a variety of purposes from study of the dynamics of the weather and climate system to projections of future climate. Weather is known as the condition of the atmosphere over a period of time, while climate has to do with the atmospheric condition over an extended to indefinite period of time.
Chinese scientist Shen Kuo inferred that climates shifted over an enormous span of time, after observing petrified bamboos found underground near Yanzhou, a dry-climate area unsuitable for the growth of bamboo. Early climate researchers include Edmund Halley, who published a map of the trade winds in 1686 after a voyage to the southern hemisphere. Benjamin Franklin first mapped the course of the Gulf Stream for use in sending mail from the United States to Europe. Francis Galton invented the term anticyclone. Helmut Landsberg fostered the use of statistical analysis in climatology, which led to its evolution into a physical science; the Greeks began the formal study of climate. The first distinct climate treaties were the works of Hippocrates, who wrote Airs and Places in 400 B. C. E. Climatology is approached in various ways such as Paleoclimatology, which seeks to reconstruct past climates by examining records such as ice cores and tree rings. Paleotempestology uses these same records to help determine hurricane frequency over millennia.
The study of contemporary climates incorporates meteorological data accumulated over many years, such as records of rainfall and atmospheric composition. Knowledge of the atmosphere and its dynamics is embodied in models, either statistical or mathematical, which help by integrating different observations and testing how they fit together. Modeling is used for understanding past and potential future climates. Historical climatology is the study of climate as related to human history and thus focuses only on the last few thousand years. Climate research is made difficult by the large scale, long time periods, complex processes which govern climate. Climate is governed by physical laws; these equations are coupled and nonlinear, so that approximate solutions are obtained by using numerical methods to create global climate models. Climate is sometimes modeled as a stochastic process but this is accepted as an approximation to processes that are otherwise too complicated to analyze. Scientists use climate indices based on several climate patterns in their attempt to characterize and understand the various climate mechanisms that culminate in our daily weather.
Much in the way the Dow Jones Industrial Average, based on the stock prices of 30 companies, is used to represent the fluctuations in the stock market as a whole, climate indices are used to represent the essential elements of climate. Climate indices are devised with the twin objectives of simplicity and completeness, each index represents the status and timing of the climate factor it represents. By their nature, indices are simple, combine many details into a generalized, overall description of the atmosphere or ocean which can be used to characterize the factors which impact the global climate system. El Niño–Southern Oscillation is a global coupled ocean-atmosphere phenomenon; the Pacific Ocean signatures, El Niño and La Niña are important temperature fluctuations in surface waters of the tropical Eastern Pacific Ocean. The name El Niño, from the Spanish for "the little boy", refers to the Christ child, because the phenomenon is noticed around Christmas time in the Pacific Ocean off the west coast of South America.
La Niña means "the little girl". Their effect on climate in the subtropics and the tropics are profound; the atmospheric signature, the Southern Oscillation reflects the monthly or seasonal fluctuations in the air pressure difference between Tahiti and Darwin. The most recent occurrence of El Niño started in September 2006 and lasted until early 2007. ENSO is a set of interacting parts of a single global system of coupled ocean-atmosphere climate fluctuations that come about as a consequence of oceanic and atmospheric circulation. ENSO is the most prominent known source of inter-annual variability in weather and climate around the world; the cycle occurs every two to seven years, with El Niño lasting nine months to two years within the longer term cycle, though not all areas globally are affected. ENSO has signatures in the Pacific and Indian Oceans. In the Pacific, during major warm events, El Niño warming extends over much of the tropical Pacific and becomes linked to the SO intensity. While ENSO events are in phase between the Pacific and Indian Ocean