Rain 1

Rain

A rain shaft at the base of a thunderstorm Torrential rain in Greece.

Part of the nature series

WeatherCalendar seasons

Spring Summer Autumn Winter

Tropical seasons

Dry season Wet season

Storms

Thunderstorm (Thundersnow) Supercell Downburst Lightning Tornado Waterspout Tropical cyclone (Hurricane) Extratropical cyclone Winter storm Blizzard Ice storm Dust storm Firestorm Cloud

Precipitation

Drizzle (Freezing drizzle) Rain (Freezing rain) Snow (Rain and snow mixed Snow grains Snow roller) Graupel Ice pellets Hail

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Rain 2

Topics

Meteorology Climate Weather forecasting Heat wave Air pollution Cold wave

Weather portal

Rain is liquid water in the form of droplets that have condensed from atmospheric water vapor and thenprecipitatedthat is, become heavy enough to fall under gravity. Rain is a major component of the water cycle andis responsible for depositing most of the fresh water on the Earth. It provides suitable conditions for many types ofecosystem, as well as water for hydroelectric power plants and crop irrigation.The major cause of rain production is moisture moving along three-dimensional zones of temperature and moisturecontrasts known as weather fronts. If enough moisture and upward motion is present, precipitation falls fromconvective clouds (those with strong upward vertical motion) such as cumulonimbus (thunder clouds) which canorganize into narrow rainbands. In mountainous areas, heavy precipitation is possible where upslope flow ismaximized within windward sides of the terrain at elevation which forces moist air to condense and fall out asrainfall along the sides of mountains. On the leeward side of mountains, desert climates can exist due to the dry aircaused by downslope flow which causes heating and drying of the air mass. The movement of the monsoon trough,or intertropical convergence zone, brings rainy seasons to savannah climes.The urban heat island effect leads to increased rainfall, both in amounts and intensity, downwind of cities. Globalwarming is also causing changes in the precipitation pattern globally, including wetter conditions across easternNorth America and drier conditions in the tropics.[citation needed] Antarctica is the driest continent. The globallyaveraged annual precipitation over land is 715 millimetres (28.1in), but over the whole Earth it is much higher at990 millimetres (39in).[1] Climate classification systems such as the Kppen climate classification system useaverage annual rainfall to help differentiate between differing climate regimes. Rainfall is measured using raingauges. Rainfall amounts can be estimated by weather radar.Rain is also known or suspected on other planets, where it may be composed of methane, neon, sulfuric acid or eveniron rather than water.

Formation

Water-saturated airAir contains water vapor and the amount of water in a given mass of dry air, known as the mixing ratio, is measuredin grams of water per kilogram of dry air (g/kg).[2][3] The amount of moisture in air is also commonly reported asrelative humidity; which is the percentage of the total water vapor air can hold at a particular air temperature.[4] Howmuch water vapor a parcel of air can contain before it becomes saturated (100%relative humidity) and forms into acloud (a group of visible and tiny water and ice particles suspended above the Earth's surface)[5] depends on itstemperature. Warmer air can contain more water vapor than cooler air before becoming saturated. Therefore, oneway to saturate a parcel of air is to cool it. The dew point is the temperature to which a parcel must be cooled inorder to become saturated.[6]

There are four main mechanisms for cooling the air to its dew point: adiabatic cooling, conductive cooling, radiational cooling, and evaporative cooling. Adiabatic cooling occurs when air rises and expands.[7] The air can rise due to convection, large-scale atmospheric motions, or a physical barrier such as a mountain (orographic lift). Conductive cooling occurs when the air comes into contact with a colder surface,[8] usually by being blown from one

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Rain 3

surface to another, for example from a liquid water surface to colder land. Radiational cooling occurs due to theemission of infrared radiation, either by the air or by the surface underneath.[9] Evaporative cooling occurs whenmoisture is added to the air through evaporation, which forces the air temperature to cool to its wet-bulb temperature,or until it reaches saturation.[10]

The main ways water vapor is added to the air are: wind convergence into areas of upward motion,[] precipitation orvirga falling from above,[11] daytime heating evaporating water from the surface of oceans, water bodies or wetland,[12] transpiration from plants,[13] cool or dry air moving over warmer water,[14] and lifting air over mountains.[]

Water vapor normally begins to condense on condensation nuclei such as dust, ice, and salt in order to form clouds.Elevated portions of weather fronts (which are three-dimensional in nature)[15] force broad areas of upward motionwithin the Earth's atmosphere which form clouds decks such as altostratus or cirrostratus.[] Stratus is a stable clouddeck which tends to form when a cool, stable air mass is trapped underneath a warm air mass. It can also form due tothe lifting of advection fog during breezy conditions.[16]

Coalescence

The shape of rain drops depend upon their size

Coalescence occurs when water droplets fuse to create larger waterdroplets. Air resistance typically causes the water droplets in a cloud toremain stationary. When air turbulence occurs, water droplets collide,producing larger droplets. As these larger water droplets descend,coalescence continues, so that drops become heavy enough toovercome air resistance and fall as rain. Coalescence generally happensmost often in clouds above freezing, and is also known as the warmrain process.[17] In clouds below freezing, when ice crystals gainenough mass they begin to fall. This generally requires more mass thancoalescence when occurring between the crystal and neighboring waterdroplets. This process is temperature dependent, as supercooled waterdroplets only exist in a cloud that is below freezing. In addition,because of the great temperature difference between cloud and groundlevel, these ice crystals may melt as they fall and become rain.[18]

Raindrops have sizes ranging from 0.1 to 9 millimetres (0.0039 to 0.35in) mean diameter, above which they tend to break up. Smaller drops are called cloud droplets, and their shape isspherical. As a raindrop increases in size, its shape becomes more oblate, with its largest cross-section facing theoncoming airflow. Large rain drops become increasingly flattened on the bottom, like hamburger buns; very largeones are shaped like parachutes.[19] Contrary to popular belief, their shape does not resemble a teardrop.[20] Thebiggest raindrops on Earth were recorded over Brazil and the Marshall Islands in 2004 some of them were aslarge as 10 millimetres (0.39in). The large size is explained by condensation on large smoke particles or bycollisions between drops in small regions with particularly high content of liquid water.[21]

Intensity and duration of rainfall are usually inversely related, i.e., high intensity storms are likely to be of shortduration and low intensity storms can have a long duration.[][22] Rain drops associated with melting hail tend to belarger than other rain drops.[23] Raindrops impact at their terminal velocity, which is greater for larger drops due totheir larger mass to drag ratio. At sea level and without wind, 0.5 millimetres (0.020in) drizzle impacts at 2 metresper second (4.5mph) (2 m/s or 6.6ft/s), while large 5 millimetres (0.20in) drops impact at around 9 metres persecond (20mph) (9 m/s or 30ft/s).[24] The sound of raindrops hitting water is caused by bubbles of air oscillatingunderwater.[25][26] The METAR code for rain is RA, while the coding for rain showers is SHRA.[]

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Rain 4

Causes

Frontal activityStratiform (a broad shield of precipitation with a relatively similar intensity) and dynamic precipitation (convectiveprecipitation which is showery in nature with large changes in intensity over short distances) occur as a consequenceof slow ascent of air in synoptic systems (on the order of cm/s), such as in the vicinity of cold fronts and near andpoleward of surface warm fronts. Similar ascent is seen around tropical cyclones outside of the eyewall, and incomma-head precipitation patterns around mid-latitude cyclones.[] A wide variety of weather can be found along anoccluded front, with thunderstorms possible, but usually their passage is associated with a drying of the air mass.Occluded fronts usually form around mature low-pressure areas.[] What separates rainfall from other precipitationtypes, such as ice pellets and snow, is the presence of a thick layer of air aloft which is above the melting point ofwater, which melts the frozen precipitation well before it reaches the ground. If there is a shallow near surface layerthat is below freezing, freezing rain (rain which freezes on contact with surfaces in subfreezing environments) willresult.[27] Hail becomes an increasingly infrequent occurrence when the freezing level within the atmosphereexceeds 11,000 feet (3,400m) above ground level.[]

Convection

Convective precipitation

Orographic precipitation

Convective rain, or showery precipitation, occurs from convectiveclouds, e.g., cumulonimbus or cumulus congestus. It falls as showerswith rapidly changing intensity. Convective precipitation falls over acertain area for a relatively short time, as convective clouds havelimited horizontal extent. Most precipitation in the tropics appears tobe convective; however, it has been suggested that stratiformprecipitation also occurs.[][28] Graupel and hail indicate convection.[29]

In mid-latitudes, convective precipitation is intermittent and oftenassociated with baroclinic boundaries such as cold fronts, squall lines,and warm fronts.[30]

Orographic effects

Orographic precipitation occurs on the windward side of mountainsand is caused by the rising air motion of a large-scale flow of moist airacross the mountain ridge, resulting in adiabatic cooling andcondensation. In mountainous parts of the world subjected to relativelyconsistent winds (for example, the trade winds), a more moist climateusually prevails on the windward side of a mountain than on theleeward or downwind side. Moisture is removed by orographic lift,leaving drier air (see katabatic wind) on the descending and generallywarming, leeward side where a rain shadow is observed.[]

In Hawaii, Mount Waialeale, on the island of Kauai, is notable for its extreme rainfall, as it has the second highestaverage annual rainfall on Earth, with 460 inches (12,000mm).[31] Systems known as Kona storms affect the statewith heavy rains between October and April.[32] Local climates vary considerably on each island due to theirtopography, divisible into windward (Koolau) and leeward (Kona) regions based upon location relative to the highermountains. Windward sides face the east to northeast trade winds and receive much more rainfall; leeward sides aredrier and sunnier, with less rain and less cloud cover.[33]

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Rain 5

In South America, the Andes mountain range blocks Pacific moisture that arrives in that continent, resulting in adesertlike climate just downwind across western Argentina.[] The Sierra Nevada range creates the same effect inNorth America forming the Great Basin and Mojave Deserts.[34][35]

Within the tropics

Rainfall distribution by month in Cairns showing the extent of thewet season at that location

The wet, or rainy, season is the time of year, coveringone or more months, when most of the average annualrainfall in a region falls.[36] The term green season isalso sometimes used as a euphemism by touristauthorities.[37] Areas with wet seasons are dispersedacross portions of the tropics and subtropics.[38]

Savanna climates and areas with monsoon regimeshave wet summers and dry winters. Tropical rainforeststechnically do not have dry or wet seasons, since theirrainfall is equally distributed through the year.[] Someareas with pronounced rainy seasons will see a break inrainfall mid-season when the intertropical convergencezone or monsoon trough move poleward of theirlocation during the middle of the warm season.[] Whenthe wet season occurs during the warm season, orsummer, rain falls mainly during the late afternoon and early evening hours. The wet season is a time when airquality improves,[39] freshwater quality improves,[40][41] and vegetation grows significantly.

Tropical cyclones, a source of very heavy rainfall, consist of large air masses several hundred miles across with lowpressure at the centre and with winds blowing inward towards the centre in either a clockwise direction (southernhemisphere) or counter clockwise (northern hemisphere).[42] Although cyclones can take an enormous toll in livesand personal property, they may be important factors in the precipitation regimes of places they impact, as they maybring much-needed precipitation to otherwise dry regions.[] Areas in their path can receive a year's worth of rainfallfrom a tropical cyclone passage.[43]

Human influence

Image of Atlanta, Georgia showing temperaturedistribution, with blue showing cool temperatures, red

warm, and hot areas appear white.

The fine particulate matter produced by car exhaust and otherhuman sources of pollution forms cloud condensation nuclei, leadsto the production of clouds and increases the likelihood of rain. Ascommuters and commercial traffic cause pollution to build up overthe course of the week, the likelihood of rain increases: it peaks bySaturday, after five days of weekday pollution has been built up.In heavily populated areas that are near the coast, such as theUnited States' Eastern Seaboard, the effect can be dramatic: thereis a 22% higher chance of rain on Saturdays than on Mondays.[44]

The urban heat island effect warms cities 0.6 C (1.1F) to 5.6 C(10.1F) above surrounding suburbs and rural areas. This extraheat leads to greater upward motion, which can induce additionalshower and thunderstorm activity. Rainfall rates downwind ofcities are increased between 48% and 116%. Partly as a result of

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Rain 6

Mean surface temperature anomalies during the period1999 to 2008 with respect to the average temperatures

from 1940 to 1980

this warming, monthly rainfall is about 28% greater between 20 to40 miles (32 to 64 km) downwind of cities, compared withupwind.[45] Some cities induce a total precipitation increase of51%.[46]

Increasing temperatures tend to increase evaporation which canlead to more precipitation. Precipitation generally increased overland north of 30N from 1900 through 2005 but has declined overthe tropics since the 1970s. Globally there has been no statisticallysignificant overall trend in precipitation over the past century,although trends have varied widely by region and over time.Eastern portions of North and South America, northern Europe,and northern and central Asia have become wetter. The Sahel, theMediterranean, southern Africa and parts of southern Asia havebecome drier. There has been an increase in the number of heavy precipitation events over many areas during thepast century, as well as an increase since the 1970s in the prevalence of droughtsespecially in the tropics andsubtropics. Changes in precipitation and evaporation over the oceans are suggested by the decreased salinity of mid-and high-latitude waters (implying more precipitation), along with increased salinity in lower latitudes (implying lessprecipitation and/or more evaporation). Over the contiguous United States, total annual precipitation increased at anaverage rate of 6.1percent since 1900, with the greatest increases within the East North Central climate region (11.6percent per century) and the South (11.1percent). Hawaii was the only region to show a decrease (-9.25percent).[47]

The most successful attempts at influencing weather involve cloud seeding which include techniques used toincrease winter precipitation over mountains and suppress hail.[]

Characteristics

Patterns

Band of thunderstorms seen on a weather radar display

Rainbands are cloud and precipitation areas which aresignificantly elongated. Rainbands can be stratiform orconvective,[48] and are generated by differences in temperature.When noted on weather radar imagery, this precipitationelongation is referred to as banded structure.[49] Rainbands inadvance of warm occluded fronts and warm fronts are associatedwith weak upward motion,[50] and tend to be wide and stratiformin nature.[51]

Rainbands spawned near and ahead of cold fronts can be squalllines which are able to produce tornadoes.[52] Rainbandsassociated with cold fronts can be warped by mountain barriersperpendicular to the front's orientation due to the formation of a low-level barrier jet.[53] Bands of thunderstorms canform with sea breeze and land breeze boundaries, if enough moisture is present. If sea breeze rainbands becomeactive enough just ahead of a cold front, they can mask the location of the cold front itself.[54]

Once a cyclone occludes, a trough of warm air aloft, or "trowal" for short, will be caused by strong southerly winds on its eastern periphery rotating aloft around its northeast, and ultimately northwestern, periphery (also known as the warm conveyor belt), forcing a surface trough to continue into the cold sector on a similar curve to the occluded front. The trowal creates the portion of an occluded cyclone known as its comma head, due to the comma-like shape of the mid-tropospheric cloudiness that accompanies the feature. It can also be the focus of locally heavy

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Rain 7

precipitation, with thunderstorms possible if the atmosphere along the trowal is unstable enough for convection.[]

Banding within the comma head precipitation pattern of an extratropical cyclone can yield significant amounts ofrain.[55] Behind extratropical cyclones during fall and winter, rainbands can form downwind of relative warm bodiesof water such as the Great Lakes. Downwind of islands, bands of showers and thunderstorms can develop due to lowlevel wind convergence downwind of the island edges. Offshore California, this has been noted in the wake of coldfronts.[56]

Rainbands within tropical cyclones are curved in orientation. Tropical cyclone rainbands contain showers andthunderstorms that, together with the eyewall and the eye, constitute a hurricane or tropical storm. The extent ofrainbands around a tropical cyclone can help determine the cyclone's intensity.[57]

Acidity

The pH of rain varies, especially due to its origin. On America's EastCoast, rain that is derived from the Atlantic Ocean typically has a pHof 5.0-5.6; rain that comes across the continental from the west has apH of 3.8-4.8; and local thunderstorms can have a pH as low as 2.0.[58]

Rain becomes acidic primarily due to the presence of two strong acids,sulfuric acid (H2SO4) and nitric acid (HNO3). Sulfuric acid is derivedfrom natural sources such as volcanoes, and wetlands (sulfate reducingbacteria); and anthropogenic sources such as the combustion of fossilfuels, and mining where H2S is present. Nitric acid is produced bynatural sources such as lightning, soil bacteria, and natural fires; while also produced anthropogenically by thecombustion of fossil fuels and from power plants. In the past 20 years the concentrations of nitric and sulfuric acidhas decreased in presence of rainwater, which may be due to the significant increase in ammonium (most likely asammonia from livestock production), which acts as a buffer in acid rain and raises the pH.[59]

Kppen climate classification

Updated Kppen-Geiger climate map (direct: Final Revised Paper)

The Kppen classification depends onaverage monthly values of temperatureand precipitation. The most commonlyused form of the Kppen classificationhas five primary types labeled Athrough E. Specifically, the primarytypes are A, tropical; B, dry; C, mildmid-latitude; D, cold mid-latitude; andE, polar. The five primaryclassifications can be further dividedinto secondary classifications such asrain forest, monsoon, tropical savanna,humid subtropical, humid continental,oceanic climate, Mediterraneanclimate, steppe, subarctic climate,tundra, polar ice cap, and desert.

Rain forests are characterized by high rainfall, with definitions setting minimum normal annual rainfall between 1,750 and 2,000 millimetres (69 and 79 in).[61] A tropical savanna is a grassland biome located in semi-arid to semi-humid climate regions of subtropical and tropical latitudes, with rainfall between 750 and 1,270 millimetres (30

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Rain 8

and 50 in) a year. They are widespread on Africa, and are also found in India, the northern parts of South America,Malaysia, and Australia.[] The humid subtropical climate zone where winter rainfall is associated with large stormsthat the westerlies steer from west to east. Most summer rainfall occurs during thunderstorms and from occasionaltropical cyclones.[62] Humid subtropical climates lie on the east side continents, roughly between latitudes 20 and40 degrees away from the equator.[63]

An oceanic (or maritime) climate is typically found along the west coasts at the middle latitudes of all the world'scontinents, bordering cool oceans, as well as southeastern Australia, and is accompanied by plentiful precipitationyear round.[64] The Mediterranean climate regime resembles the climate of the lands in the Mediterranean Basin,parts of western North America, parts of Western and South Australia, in southwestern South Africa and in parts ofcentral Chile. The climate is characterized by hot, dry summers and cool, wet winters.[65] A steppe is a drygrassland.[66] Subarctic climates are cold with continuous permafrost and little precipitation.[]

Measurement

Gauges

Standard rain gauge

Rain is measured in units of length per unit time, typically in millimeters per hour,[67] orin countries where imperial units are more common, inches per hour.[68] The "length", ormore accurately, "depth" being measured is the depth of rain water that would accumulateon a flat, horizontal and impermeable surface during a given amount of time, typically anhour.[69] One millimeter of rainfall is the equivalent of one liter of water per squaremeter.[70]

The standard way of measuring rainfall or snowfall is the standard rain gauge, which canbe found in 100-mm (4-in) plastic and 200-mm (8-in) metal varieties.[71] The innercylinder is filled by 25mm (0.98in) of rain, with overflow flowing into the outer cylinder.Plastic gauges have markings on the inner cylinder down to 0.25mm (0.0098in)resolution, while metal gauges require use of a stick designed with the appropriate0.25mm (0.0098in) markings. After the inner cylinder is filled, the amount inside it isdiscarded, then filled with the remaining rainfall in the outer cylinder until all the fluid inthe outer cylinder is gone, adding to the overall total until the outer cylinder is empty.[72]

Other types of gauges include the popular wedge gauge (the cheapest rain gauge and most fragile), the tipping bucketrain gauge, and the weighing rain gauge.[73] For those looking to measure rainfall the most inexpensively, a can thatis cylindrical with straight sides will act as a rain gauge if left out in the open, but its accuracy will depend on whatruler is used to measure the rain with. Any of the above rain gauges can be made at home, with enoughknow-how.[74]

When a precipitation measurement is made, various networks exist across the United States and elsewhere whererainfall measurements can be submitted through the Internet, such as CoCoRAHS or GLOBE.[75][76] If a network isnot available in the area where one lives, the nearest local weather or met office will likely be interested in themeasurement.[77]

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Rain 9

Remote sensing

Twenty-four hour rainfall accumulation on the Vald'Irne radar in Eastern Canada. Zones without data inthe east and southwest are caused by beam blocking

from mountains. (Source: Environment Canada)

One of the main uses of weather radar is to be able to assess theamount of precipitations fallen over large basins for hydrologicalpurposes.[78] For instance, river flood control, sewer managementand dam construction are all areas where planners use rainfallaccumulation data. Radar-derived rainfall estimates complimentsurface station data which can be used for calibration. To produceradar accumulations, rain rates over a point are estimated by usingthe value of reflectivity data at individual grid points. A radarequation is then used, which is,

,where Z represents the radar reflectivity, R represents the rainfallrate, and A and b are constants.[79] Satellite derived rainfallestimates use passive microwave instruments aboard polar orbitingas well as geostationary weather satellites to indirectly measurerainfall rates.[80] If one wants an accumulated rainfall over a time period, one has to add up all the accumulationsfrom each grid box within the images during that time.

1988 Rain in the U.S. The heaviest rain is seen in reds and yellows.

1993 Rain in the U.S.

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Rain 10

IntensityRainfall intensity is classified according to the rate of precipitation: Light rain when the precipitation rate is < 2.5 millimetres (0.098in) per hour Moderate rain when the precipitation rate is between 2.5 millimetres (0.098in) - 7.6 millimetres (0.30in) or 10

millimetres (0.39in) per hour[][]

Heavy rain when the precipitation rate is > 7.6 millimetres (0.30in) per hour,[] or between 10 millimetres(0.39in) and 50 millimetres (2.0in) per hour[]

Violent rain when the precipitation rate is > 50 millimetres (2.0in) per hour[]

Euphemisms for a heavy or violent rain include gully washer, trash-mover and toad-strangler.[81][82]

Return periodThe likelihood or probability of an event with a specified intensity and duration, is called the return period orfrequency.[83] The intensity of a storm can be predicted for any return period and storm duration, from charts basedon historic data for the location.[84] The term 1 in 10year storm describes a rainfall event which is rare and is onlylikely to occur once every 10years, so it has a 10percent likelihood any given year. The rainfall will be greater andthe flooding will be worse than the worst storm expected in any single year. The term 1 in 100year storm describes arainfall event which is extremely rare and which will occur with a likelihood of only once in a century, so has a1percent likelihood in any given year. The rainfall will be extreme and flooding to be worse than a 1 in 10yearevent. As with all probability events, it is possible, though improbable, to have multiple "1 in 100Year Storms" in asingle year.[85]

Forecasting

Example of a five-day rainfall forecast from theHydrometeorological Prediction Center

The Quantitative Precipitation Forecast (abbreviated QPF) is theexpected amount of liquid precipitation accumulated over aspecified time period over a specified area.[] A QPF will bespecified when a measurable precipitation type reaching aminimum threshold is forecast for any hour during a QPF validperiod. Precipitation forecasts tend to be bound by synoptic hourssuch as 0000, 0600, 1200 and 1800GMT. Terrain is considered inQPFs by use of topography or based upon climatologicalprecipitation patterns from observations with fine detail.[86]

Starting in the mid to late 1990s, QPFs were used withinhydrologic forecast models to simulate impact to rivers throughout the United States.[87] Forecast models showsignificant sensitivity to humidity levels within the planetary boundary layer, or in the lowest levels of theatmosphere, which decreases with height.[88] QPF can be generated on a quantitative, forecasting amounts, or aqualitative, forecasting the probability of a specific amount, basis.[89] Radar imagery forecasting techniques showhigher skill than model forecasts within 6 to 7hours of the time of the radar image. The forecasts can be verifiedthrough use of rain gauge measurements, weather radar estimates, or a combination of both. Various skill scores canbe determined to measure the value of the rainfall forecast.[]

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Rain 11

Impact

Effect on agriculturePrecipitation, especially rain, has a dramatic effect on agriculture. All plants need at least some water to survive,therefore rain (being the most effective means of watering) is important to agriculture. While a regular rain pattern isusually vital to healthy plants, too much or too little rainfall can be harmful, even devastating to crops. Drought cankill crops and increase erosion,[90] while overly wet weather can cause harmful fungus growth.[91] Plants needvarying amounts of rainfall to survive. For example, certain cacti require small amounts of water,[92] while tropicalplants may need up to hundreds of inches of rain per year to survive.In areas with wet and dry seasons, soil nutrients diminish and erosion increases during the wet season.[] Animalshave adaptation and survival strategies for the wetter regime. The previous dry season leads to food shortages intothe wet season, as the crops have yet to mature.[93] Developing countries have noted that their populations showseasonal weight fluctuations due to food shortages seen before the first harvest, which occurs late in the wetseason.[94] Rain may be harvested through the use of rainwater tanks; treated to potable use or for non-potable useindoors or for irrigation.[95] Excessive rain during short periods of time can cause flash floods.[96]

In cultureCultural attitudes towards rain differ across the world. In temperate climates, people tend to be more stressed whenthe weather is unstable or cloudy, with its impact greater on men than women.[97] Rain can also bring joy, as someconsider it to be soothing or enjoy the aesthetic appeal of it. In dry places, such as India,[98] or during periods ofdrought,[99] rain lifts people's moods. In Botswana, the Setswana word for rain, "pula", is used as the name of thenational currency, in recognition of the economic importance of rain in this desert country.[100] Several cultures havedeveloped means of dealing with rain and have developed numerous protection devices such as umbrellas andraincoats, and diversion devices such as gutters and storm drains that lead rains to sewers.[101] Many people find thescent during and immediately after rain pleasant or distinctive. The source of this scent is petrichor, an oil producedby plants, then absorbed by rocks and soil, and later released into the air during rainfall.[]

Global climatologyApproximately 505,000 cubic kilometres (121,000cumi) of water falls as precipitation each year across the globewith 398,000 cubic kilometres (95,000cumi) of it over the oceans.[] Given the Earth's surface area, that means theglobally averaged annual precipitation is 990 millimetres (39in). Deserts are defined as areas with an average annualprecipitation of less than 250 millimetres (10in) per year,[][102] or as areas where more water is lost byevapotranspiration than falls as precipitation.[]

Deserts

Largest deserts

The northern half of Africa is primarilydesert or arid, containing the Sahara. AcrossAsia, a large annual rainfall minimum,composed primarily of deserts, stretchesfrom the Gobi desert in Mongoliawest-southwest through western Pakistan(Balochistan) and Iran into the Arabiandesert in Saudi Arabia. Most of Australia is

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Rain 12

semi-arid or desert,[103] making it the world's driest inhabited continent. In South America, the Andes mountainrange blocks Pacific moisture that arrives in that continent, resulting in a desertlike climate just downwind acrosswestern Argentina.[] The drier areas of the United States are regions where the Sonoran desert overspreads the DesertSouthwest, the Great Basin and central Wyoming.[]

Polar desertSince rain only falls as liquid, in frozen temperatures, rain can not fall. As a result, very cold climates see very littlerainfall and are often known as polar deserts. A common biome in this area is the tundra which has a short summerthaw and a long frozen winter. Ice caps see no rain at all, making Antarctica the world's driest continent.

RainforestsRainforests are areas of the world with very high rainfall. Both tropical and temperate rainforests exist. Tropicalrainforests occupy a large band of the planet mostly along the equator. Most temperate rainforests are located onmountainous west coasts between 45 and 55 degrees latitude, but they are often found in other areas.Around 40-75% of all biotic life is found in rainforests. Rainforests are also responsible for 28% of the world'soxygen turnover.

MonsoonsThe equatorial region near the Intertropical Convergence Zone (ITCZ), or monsoon trough, is the wettest portion ofthe world's continents. Annually, the rain belt within the tropics marches northward by August, then moves backsouthward into the Southern Hemisphere by February and March.[104] Within Asia, rainfall is favored across itssouthern portion from India east and northeast across the Philippines and southern China into Japan due to themonsoon advecting moisture primarily from the Indian Ocean into the region.[105] The monsoon trough can reach asfar north as the 40th parallel in East Asia during August before moving southward thereafter. Its polewardprogression is accelerated by the onset of the summer monsoon which is characterized by the development of lowerair pressure (a thermal low) over the warmest part of Asia.[][106] Similar, but weaker, monsoon circulations arepresent over North America and Australia.[107][108] During the summer, the Southwest monsoon combined with Gulfof California and Gulf of Mexico moisture moving around the subtropical ridge in the Atlantic ocean bring thepromise of afternoon and evening thunderstorms to the southern tier of the United States as well as the GreatPlains.[109] The eastern half of the contiguous United States east of the 98th meridian, the mountains of the PacificNorthwest, and the Sierra Nevada range are the wetter portions of the nation, with average rainfall exceeding 30inches (760mm) per year.[110] Tropical cyclones enhance precipitation across southern sections of the UnitedStates,[111] as well as Puerto Rico, the United States Virgin Islands,[112] the Northern Mariana Islands,[113] Guam,and American Samoa.

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Rain 13

Impact of the Westerlies

Long-term mean precipitation by month

Westerly flow from the mild northAtlantic leads to wetness acrosswestern Europe, in particular Irelandand the United Kingdom, where thewestern coasts can receive between1,000mm (39in), at sea-level and2,500mm (98in), on the mountains ofrain per year. Bergen, Norway is oneof the more famous Europeanrain-cities with its yearly precipitationof 2,250mm (89in) on average.During the fall, winter, and spring,Pacific storm systems bring most ofHawaii and the western United Statesmuch of their precipitation.[109] Overthe top of the ridge, the jet stream brings a summer precipitation maximum to the Great Lakes. Large thunderstormareas known as mesoscale convective complexes move through the Plains, Midwest, and Great Lakes during thewarm season, contributing up to 10% of the annual precipitation to the region.[114]

The El Nio-Southern Oscillation affects the precipitation distribution, by altering rainfall patterns across thewestern United States,[115] Midwest,[116][117] the Southeast,[118] and throughout the tropics. There is also evidencethat global warming is leading to increased precipitation to the eastern portions of North America, while droughts arebecoming more frequent in the tropics and subtropics.

Wettest known locationsCherrapunji, situated on the southern slopes of the Eastern Himalaya in Shillong, India is the confirmed wettestplaces on Earth, with an average annual rainfall of 11,430mm (450in). The highest recorded rainfall in a single yearwas 22,987mm (905.0in) in 1861. The 38-year average at nearby Mawsynram, Meghalaya, India is 11,873mm(467.4in).[119] The wettest spot in Australia is Mount Bellenden Ker in the north-east of the country which recordsan average of 8,000 millimetres (310in) per year, with over 12,200mm (480.3in) of rain recorded during 2000.[120]

Mount Waialeale on the island of Kauai in the Hawaiian Islands averages more than 11,680 millimetres (460in) ofrain per year over the last 32 years, with a record 17,340 millimetres (683in) in 1982. Its summit is considered oneof the rainiest spots on earth. It has been promoted in tourist literature for many years as the wettest spot in theworld.[121] Llor, a town situated in Choc, Colombia, is probably the place with the largest measured rainfall in theworld, averaging 13,300mm (520in) per year.[] The Department of Choc is extraordinarily humid. Tutunendo, asmall town situated in the same department, is one of the wettest estimated places on Earth, averaging 11,394mm(448.6in) per year; in 1974 the town received 26,303mm (86ft3.6in), the largest annual rainfall measured inColombia. Unlike Cherrapunji, which receives most of its rainfall between April and September, Tutunendo receivesrain almost uniformly distributed throughout the year.[122] Quibd, the capital of Choc, receives the most rain in theworld among cities with over 100,000 inhabitants: 9,000 millimetres (350in) per year.[] Storms in Choc can drop500mm (20in) of rainfall in a day. This amount is more than falls in many cities in a year's time.

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Rain 14

Continent Highest average Place Elevation Years ofRecord

in mm ft m

South America 523.6 13,299 Llor, Colombia (estimated)[a][b] 520 158[c] 29

Asia 467.4 11,872 Mawsynram, India[a][d] 4,597 1,401 39

Oceania 460.0 11,684 Mount Waialeale, Kauai, Hawaii(USA)[a]

5,148 1,569 30

Africa 405.0 10,287 Debundscha, Cameroon 30 9.1 32

South America 354.0 8,992 Quibdo, Colombia 120 36.6 16

Australia 340.0 8,636 Mount Bellenden Ker, Queensland 5,102 1,555 9

North America 256.0 6,502 Henderson Lake, British Columbia 12 3.66 14

Europe 183.0 4,648 Crkvice, Montenegro 3,337 1,017 22

Source (without conversions): Global Measured Extremes of Temperature and Precipitation, National Climatic Data Center. August 9, 2004.[123]

Continent Place Highest rainfall

in mm

Highest average annual rainfall[] Asia Mawsynram, India 467.4 11,870

Highest in one year[] Asia Cherrapunji, India 1,042 26,470

Highest in one Calendar month[] Asia Cherrapunji, India 366 9,296

Highest in 24 hours[] Indian Ocean Foc Foc, La Reunion Island 71.8 1,820

Highest in 12 hours[] Indian Ocean Foc Foc, La Reunion Island 45.0 1,140

Highest in one minute[] North America Unionville, Maryland, USA 1.23 31.2

Outside of EarthOn Titan, Saturn's largest moon, infrequent methane rain is thought to carve the moon's numerous surfacechannels.[124] On Venus, sulfuric acid virga evaporates 25 kilometres (16mi) from the surface.[125] There is likely tobe rain of various compositions in the upper atmospheres of the gas giants, as well as precipitation of liquid neon inthe deep atmospheres.[][126] Extrasolar planet OGLE-TR-56b in the constellation Sagittarius is hypothesized to haveiron rain.[127]

Notes a b c The value given is continent's highest and possibly the world's depending on measurement practices,

procedures and period of record variations. ^ The official greatest average annual precipitation for South America is 354inches at Quibdo, Colombia. The

523.6inches average at Lloro, Colombia [14 miles SE and at a higher elevation than Quibdo] is an estimatedamount.

^ Approximate elevation. ^ Recognized as "The Wettest place on Earth" by the Guinness Book of World Records.[128]

http://en.wikipedia.org/w/index.php?title=South_Americahttp://en.wikipedia.org/w/index.php?title=Llor%C3%B3http://en.wikipedia.org/w/index.php?title=Colombiahttp://en.wikipedia.org/w/index.php?title=Asiahttp://en.wikipedia.org/w/index.php?title=Mawsynramhttp://en.wikipedia.org/w/index.php?title=Indiahttp://en.wikipedia.org/w/index.php?title=Oceaniahttp://en.wikipedia.org/w/index.php?title=Mount_Waialealehttp://en.wikipedia.org/w/index.php?title=Kauaihttp://en.wikipedia.org/w/index.php?title=Hawaii_Islandshttp://en.wikipedia.org/w/index.php?title=Hawaii_Islandshttp://en.wikipedia.org/w/index.php?title=Africahttp://en.wikipedia.org/w/index.php?title=Debundschahttp://en.wikipedia.org/w/index.php?title=Cameroonhttp://en.wikipedia.org/w/index.php?title=Quibdohttp://en.wikipedia.org/w/index.php?title=Australia_%28continent%29http://en.wikipedia.org/w/index.php?title=Mount_Bellenden_Kerhttp://en.wikipedia.org/w/index.php?title=Queenslandhttp://en.wikipedia.org/w/index.php?title=North_Americahttp://en.wikipedia.org/w/index.php?title=Henderson_Lake_%28British_Columbia%29http://en.wikipedia.org/w/index.php?title=British_Columbiahttp://en.wikipedia.org/w/index.php?title=Europehttp://en.wikipedia.org/w/index.php?title=Crkvicehttp://en.wikipedia.org/w/index.php?title=Montenegrohttp://en.wikipedia.org/w/index.php?title=National_Climatic_Data_Centerhttp://en.wikipedia.org/w/index.php?title=Mawsynram%2C_Indiahttp://en.wikipedia.org/w/index.php?title=Cherrapunji%2C_Indiahttp://en.wikipedia.org/w/index.php?title=Indian_Oceanhttp://en.wikipedia.org/w/index.php?title=La_Reunion_Islandhttp://en.wikipedia.org/w/index.php?title=Unionville%2C_Talbot_County%2C_Marylandhttp://en.wikipedia.org/w/index.php?title=Titan_%28moon%29http://en.wikipedia.org/w/index.php?title=Saturnhttp://en.wikipedia.org/w/index.php?title=Venushttp://en.wikipedia.org/w/index.php?title=Virgahttp://en.wikipedia.org/w/index.php?title=Gas_gianthttp://en.wikipedia.org/w/index.php?title=OGLE-TR-56bhttp://en.wikipedia.org/w/index.php?title=Sagittarius_%28constellation%29http://en.wikipedia.org/w/index.php?title=Guinness_Book_of_World_Records

Rain 15

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[56] Ivory J. Small (1999). An observation study of island effect bands: precipitation producers in Southern California. (http:/ / www. wrh. noaa.gov/ wrh/ 99TAs/ 9918/ index. html) Retrieved on 2008-12-26.

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Chapter%206. pdf[69] Rain gauge and cubic inches (http:/ / www. newton. dep. anl. gov/ askasci/ gen99/ gen99115. htm)[81] Gullywasher | Define Gullywasher at Dictionary.com (http:/ / dictionary. reference. com/ browse/ gullywasher)[82] toad-strangler - Wiktionary (http:/ / en. wiktionary. org/ wiki/ toad-strangler)[93] A. Roberto Frisancho (1993). Human Adaptation and Accommodation. (http:/ / books. google. com/ books?id=-K_SYHBo42MC&

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precipitation. html) Retrieved on 2008-03-09.[112] Central Intelligence Agency. The World Factbook Virgin Islands. (https:/ / www. cia. gov/ library/ publications/ the-world-factbook/

geos/ vq. html) Retrieved on 2008-03-19.[113] BBC. Weather Centre - World Weather - Country Guides - Northern Mariana Islands. (http:/ / www. bbc. co. uk/ weather/ world/

country_guides/ results. shtml?tt=TT004880) Retrieved on 2008-03-19.[114] Walker S. Ashley, Thomas L. Mote, P. Grady Dixon, Sharon L. Trotter, Emily J. Powell, Joshua D. Durkee, and Andrew J. Grundstein.

Distribution of Mesoscale Convective Complex Rainfall in the United States. (http:/ / ams. allenpress. com/ archive/ 1520-0493/ 131/ 12/ pdf/i1520-0493-131-12-3003. pdf) Retrieved on 2008-03-02.

[115] John Monteverdi and Jan Null. Western Region Technical Attachment NO. 97-37 November 21, 1997: El Nio and CaliforniaPrecipitation. (http:/ / tornado. sfsu. edu/ geosciences/ elnino/ elnino. html) Retrieved on 2008-02-28.

[118] Climate Prediction Center. El Nio (ENSO) Related Rainfall Patterns Over the Tropical Pacific. (http:/ / www. cpc. noaa. gov/ products/analysis_monitoring/ ensocycle/ ensorain. shtml) Retrieved on 2008-02-28.

[128] UFL - Dispute between Mawsynram and Cherrapunji for the rainiest place in the world (http:/ / www. clas. ufl. edu/ users/ jsouthwo/ web/6-per-page-Wettest-Mawsynram-in-India. pdf)

http://www.soest.hawaii.edu/MET/Faculty/businger/PDF/BowEchoPPR.pdfhttp://www.soest.hawaii.edu/MET/Faculty/businger/PDF/BowEchoPPR.pdfhttp://amsglossary.allenpress.com/glossary/search?p=1&query=rainband&submit=Searchhttp://amsglossary.allenpress.com/glossary/search?id=banded-structure1http://adsabs.harvard.edu/abs/1988PhDT.......110Hhttp://adsabs.harvard.edu/abs/1988PhDT.......110Hhttp://books.google.com/books?id=4KXtnQ3bDeEC&pg=PA405&lpg=PA405&dq=sea+breeze+rainbands&source=bl&ots=CL5KD0HLAJ&sig=Gz5bwKi9yu8j25EbXLD3TVNNQ68&hl=en&sa=X&oi=book_result&resnum=10&ct=resulthttp://books.google.com/books?id=4KXtnQ3bDeEC&pg=PA405&lpg=PA405&dq=sea+breeze+rainbands&source=bl&ots=CL5KD0HLAJ&sig=Gz5bwKi9yu8j25EbXLD3TVNNQ68&hl=en&sa=X&oi=book_result&resnum=10&ct=resulthttp://books.google.com/books?id=4KXtnQ3bDeEC&pg=PA405&lpg=PA405&dq=sea+breeze+rainbands&source=bl&ots=CL5KD0HLAJ&sig=Gz5bwKi9yu8j25EbXLD3TVNNQ68&hl=en&sa=X&oi=book_result&resnum=10&ct=resulthttp://amsglossary.allenpress.com/glossary/search?id=prefrontal-squall-line1http://cat.inist.fr/?aModele=afficheN&cpsidt=2721180http://cat.inist.fr/?aModele=afficheN&cpsidt=2721180http://cat.inist.fr/?aModele=afficheN&cpsidt=3570629http://cat.inist.fr/?aModele=afficheN&cpsidt=3570629http://cstar.cestm.albany.edu/CAP_Projects/Project4/Banded%20Precip/novakWAF.pdfhttp://cstar.cestm.albany.edu/CAP_Projects/Project4/Banded%20Precip/novakWAF.pdfhttp://www.wrh.noaa.gov/wrh/99TAs/9918/index.htmlhttp://www.wrh.noaa.gov/wrh/99TAs/9918/index.htmlhttp://en.wikipedia.org/w/index.php?title=University_of_Wisconsin%E2%80%93Madisonhttp://cimss.ssec.wisc.edu/tropic/research/products/dvorak/odt.htmlhttp://cimss.ssec.wisc.edu/tropic/research/products/dvorak/odt.htmlhttp://www.hydrol-earth-syst-sci.net/11/1633/2007/hess-11-1633-2007.pdfhttp://www.wmo.int/pages/prog/www/IMOP/publications/CIMO-Guide/CIMO%20Guide%207th%20Edition,%202008/Part%20I/Chapter%206.pdfhttp://www.wmo.int/pages/prog/www/IMOP/publications/CIMO-Guide/CIMO%20Guide%207th%20Edition,%202008/Part%20I/Chapter%206.pdfhttp://www.newton.dep.anl.gov/askasci/gen99/gen99115.htmhttp://dictionary.reference.com/browse/gullywasherhttp://en.wiktionary.org/wiki/toad-stranglerhttp://en.wikipedia.org/w/index.php?title=A._Roberto_Frisanchohttp://books.google.com/books?id=-K_SYHBo42MC&pg=PA388&lpg=PA388&dq=wet+season+characteristics&source=web&ots=QSA_t3uuZU&sig=iin9pzOynVHyA7x4wMYEkApeCV8&hl=en&sa=X&oi=book_result&resnum=5&ct=resulthttp://books.google.com/books?id=-K_SYHBo42MC&pg=PA388&lpg=PA388&dq=wet+season+characteristics&source=web&ots=QSA_t3uuZU&sig=iin9pzOynVHyA7x4wMYEkApeCV8&hl=en&sa=X&oi=book_result&resnum=5&ct=resulthttp://books.google.com/books?id=-K_SYHBo42MC&pg=PA388&lpg=PA388&dq=wet+season+characteristics&source=web&ots=QSA_t3uuZU&sig=iin9pzOynVHyA7x4wMYEkApeCV8&hl=en&sa=X&oi=book_result&resnum=5&ct=resulthttp://pubs.usgs.gov/gip/deserts/what/http://en.wikipedia.org/w/index.php?title=Peveril_Meigshttp://en.wikipedia.org/w/index.php?title=Bureau_of_Meteorologyhttp://www.bom.gov.au/weather/sa/giles/climate.shtmlhttp://www.met.utah.edu/jhorel/html/wx/climate/normrain.htmlhttp://www.nationalatlas.gov/printable/precipitation.htmlhttp://www.nationalatlas.gov/printable/precipitation.htmlhttp://en.wikipedia.org/w/index.php?title=Central_Intelligence_Agencyhttps://www.cia.gov/library/publications/the-world-factbook/geos/vq.htmlhttps://www.cia.gov/library/publications/the-world-factbook/geos/vq.htmlhttp://en.wikipedia.org/w/index.php?title=BBChttp://www.bbc.co.uk/weather/world/country_guides/results.shtml?tt=TT004880http://www.bbc.co.uk/weather/world/country_guides/results.shtml?tt=TT004880http://ams.allenpress.com/archive/1520-0493/131/12/pdf/i1520-0493-131-12-3003.pdfhttp://ams.allenpress.com/archive/1520-0493/131/12/pdf/i1520-0493-131-12-3003.pdfhttp://tornado.sfsu.edu/geosciences/elnino/elnino.htmlhttp://en.wikipedia.org/w/index.php?title=Climate_Prediction_Centerhttp://www.cpc.noaa.gov/products/analysis_monitoring/ensocycle/ensorain.shtmlhttp://www.cpc.noaa.gov/products/analysis_monitoring/ensocycle/ensorain.shtmlhttp://www.clas.ufl.edu/users/jsouthwo/web/6-per-page-Wettest-Mawsynram-in-India.pdfhttp://www.clas.ufl.edu/users/jsouthwo/web/6-per-page-Wettest-Mawsynram-in-India.pdf

Rain 16

External links What are clouds, and why does it rain? (http:/ / www. geography-site. co. uk/ pages/ physical/ climate/ why does

it rain. html) BBC article on the weekend rain effect (http:/ / news. bbc. co. uk/ 2/ hi/ sci/ tech/ 146120. stm) BBC article on rain-making (http:/ / news. bbc. co. uk/ 2/ hi/ asia-pacific/ 3893671. stm) BBC article on the mathematics of running in the rain (http:/ / news. bbc. co. uk/ 1/ hi/ magazine/ 4562132. stm)

http://www.geography-site.co.uk/pages/physical/climate/why%20does%20it%20rain.htmlhttp://www.geography-site.co.uk/pages/physical/climate/why%20does%20it%20rain.htmlhttp://news.bbc.co.uk/2/hi/sci/tech/146120.stmhttp://news.bbc.co.uk/2/hi/asia-pacific/3893671.stmhttp://news.bbc.co.uk/1/hi/magazine/4562132.stm

Article Sources and Contributors 17

Article Sources and ContributorsRain Source: http://en.wikipedia.org/w/index.php?oldid=560390074 Contributors: -Midorihana-, 12 Noon, 16@r, 42secondpoo, A.Z., A8UDI, ABlake, ADDFG Spy, Aarktica, AaronBrenneman, Abrech, Abscissa, Accurizer, Achurch, Acroterion, AdamNeallThompson, Adrian.benko, Aexon79, Agradman, Ahoerstemeier, Ahpook, Ahuskay, Aitias, Alex.tan, Alexbuirds,Alexnevzorov, Alice21397, Altenmann, Anaraug, Anclation, Andonic, Andycjp, Andyh144, Anetode, Angela, Angus Lepper, Animum, Aniten21, Anlace, Anonyminity9k, AnonymousDissident, Antandrus, Aphidoidea, Aquabarrel, Art and Muscle, Asa Gaston, Ashanda, Ashantifan1224, Ashlux, Aucitypops, Aurora, AvicAWB, AxelBoldt, Axpen, BD2412, Babbage,Badgernet, Barneyboo, Bazonka, Bejnar, Beland, Bento00, Beyond silence, Bfigura's puppy, Bhadani, Bidgee, Big Bird, Big Brother 1984, Bigbluefish, Binadot, Blehfu, Blim8183, Bobbarker2,Bobbytheonlyone, Bongomatic, Bongwarrior, Boothy443, BoundaryRider, Bradcraig53, Brandmeister, Brandmeister (old), Brian Pearson, Bruce1ee, Bubbles1234554321999, Buddha24,Burgercat, Buttman12, Bwbullough, CIreland, CSWarren, Caltas, Calum wray, CambridgeBayWeather, Camo lord, Canadian-Bacon, Carlwev, Carnby, Carnildo, Catcrazy5, CattleGirl,Cbrown285, Cenarium, Ceyockey, Chavando, Chris Capoccia, Chris the speller, Chriswaterguy, Chun-hian, Ciroa, Ckelsh, Clam-man2000, Cleared as filed, Clemwang, Cometstyles,CommonsDelinker, Conversion script, Cookie90, Corn cheese, Corpx, Courcelles, Cptbobobo, CrazyC83, Cserlajos, Cvene64, D, D climacus, D0nth4t3m3, DHN, DVD R W, Dac04, DanielCD,DarkFalls, Darkcyshadow, Darrenhusted, David.Mestel, Davidhorman, Dawnseeker2000, DeadlyAssassin, Demize, Den fjttrade ankan, Denni, Digikc94, Discospinster, Diyako, Djinn112, Dlae,Dlohcierekim's sock, Docu, Dodo von den Bergen, Donarreiskoffer, Drmies, Dunnob, Dv82matt, Dycedarg, Dylan Lake, Dylblad, Dysepsion, Dzubint, ESkog, Eagleamn, Earthandsky, Ed8r,Edal, Edgar181, Edison, Ego White Tray, Ehrenkater, Elassint, Elkman, Elusive...yup, Embokias, Emersoni, Emmarhian, EmoWiki, Emperorbma, Emx, Epbr123, Episcopo, Eran of Arcadia,Erpankajj, Esolbiz, Ethanbball, Evan Zeman, Everard Proudfoot, EverettColdwell, Everyking, Ewulp, Excirial, Eyreland, Falconguy4, Famartin, Fantasticxo, Farmercarlos, FastLizard4, Favonian,Faz90, Fergusq, Fetchcomms, Feydey, Fir0002, Fireice, Firsfron, Fl, FlavrSavr, Foledman, Fortdj33, Foxj, Franz-kafka, Funnyfarmofdoom, GB fan, Gaius Cornelius, Gene Nygaard, GeneralIroh,Geocachernemesis, Ghirlandajo, Giftlite, Gilgamesh, Gilliam, Giuliopp, Glenn, Gmip, Godriscoll334, Gogo Dodo, Gondaje, Gregisfat2, Grunt, Gunmetal Angel, Gurch, Gzkn, H2O, H2g2bob,Hadal, Hajjmaster5, HalfShadow, HansHermans, HarryHenryGebel, Hasek is the best, Heimstern, Hekerui, Hello32020, Henry Flower, Herbee, Herbivore, HeroGiant, Heron, Hiberniantears,Hohum, Hotdawg57, Husond, Hut 8.5, Hydrargyrum, Hydrogen Iodide, Ianisalifestyle, IceCreamAntisocial, Ikanreed, Ikariam3944, 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MBisanz, MDub2011, MER-C, MPerel, MacTire02, MacsBug, Mag7cute, Majorly, Malcolmxl5, Malinaccier, Malo, Man vyi, Mangwanani,Martarius, Massimo Catarinella, Matt5797, Maxim, Mbz1, Mechanical digger, Menchi, Metricmike, Meursault2004, Minimac, Mmdoogie, Mmoneypenny, Modulatum, Moe Epsilon, Moncrief,Monster eagle, Mr.courtney, Mrh30, Mschlindwein, Muriel Gottrop, Musicmant, Mww113, Myanw, NCurse, Nakon, Nateforthree, Nathan Johnson, NawlinWiki, Nayvik, Nburden, Nepenthes,Nerdge, Nergaal, Netknowle, Netsnipe, Never give in, NewEnglandYankee, Nibuod, Nick Number, Night Gyr, Nivix, Nk, Nlitement, Nochoje, Nod2003, Northamerica1000, Nubertuber,Nuujinn, O, Ocean Shores, Oda Mari, Oh.la.la.22, Ojigiri, Okedem, Omegatron, Omicronpersei8, Oneiros, Oowoo, Opelio, OrchDorkdotcom, Originalwana, Ouishoebean, Oxymoron83, P30Carl,Paleorthid, Paolo.dL, Paranoid, Pb30, Pbroks13, Pde, PeTeRsN, Pearle, Pedro, Perfect Proposal, Persian Poet Gal, Peruvianllama, Peter Hitchmough, Peter Horn, Peter Karlsen, Petergargano,Philip Trueman, Pinethicket, Piper Brodi, Pne, Poindexter Propellerhead, Polyamorph, Polylerus, Polynova, Possum, Prashanthns, ProfDEH, Psmith, Psym, Puchiko, Puffin, Pyrotec, Qrc2006,Quelnjim, Quercusrobur, Quicksilvre, RL0919, RTucker, Rachiddebbagh, RadRafe, Radionactive, Radon210, Ragesoss, RainbowOfLight, Raincheerleader, Raku2040, Ranemanoj, Rapparee71,Rashed, Ratiocinate, Raven42, Razorflame, Rd232, RedWolf, Reinthal, Rena2, ReqEngineer, Retiono Virginian, RexNL, Rgoodermote, Rich Farmbrough, Richardcavell, Rjd0060, Rjwilmsi, RobHooft, Rob Lindsey, Robert Sparkinton, Rojomoke, Romanm, Rpophessagr, Runner5k, Runningonbrains, Ruth-2013, RyanCross, Ryulong, Sam Li, Sanaw, Sandcherry, Sanfy, Sango123, Sanya,Scarian, Scetoaux, Schewek, Sciurin, Scm83x, Scott Roy Atwood, Sebastian.macdougal, SebastianHelm, Seishirou Sakurazuka, Senator Palpatine, Sgv 6618, Shalom Yechiel, Shanes,Shawnbird, Sherool, Shimonnyman, Shiragiku, Shizhao, Shrimppesto, Siim, SilentC, SimonP, 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Image Sources, Licenses and ContributorsFile:FoggDam-NT.jpg Source: http://en.wikipedia.org/w/index.php?title=File:FoggDam-NT.jpg License: Creative Commons Attribution 3.0 Contributors: BidgeeFile:Rain-on-Thassos.jpg Source: http://en.wikipedia.org/w/index.php?title=File:Rain-on-Thassos.jpg License: Creative Commons Attribution-Sharealike 3.0 Contributors: Edal AntonLefterovFile:Cumulus clouds in fair weather.jpeg Source: http://en.wikipedia.org/w/index.php?title=File:Cumulus_clouds_in_fair_weather.jpeg License: Creative Commons Attribution-Sharealike 2.0Contributors: Conscious, Pierre cb, Twinsday, Yarnalgo, var Arnfjr Bjarmason, 1 anonymous editsFile:Raindrops sizes.svg Source: http://en.wikipedia.org/w/index.php?title=File:Raindrops_sizes.svg License: Creative Commons Attribution 3.0 Contributors: Pbroks13File:Konvektionsregen.jpg Source: http://en.wikipedia.org/w/index.php?title=File:Konvektionsregen.jpg License: GNU Free Documentation License Contributors: Bapho, Saperaud, SeverinHeiniger, Upior polnocyFile:Steigungsregen.jpg Source: http://en.wikipedia.org/w/index.php?title=File:Steigungsregen.jpg License: GNU Free Documentation License Contributors: Dbenzhuser, Factumquintus,Saperaud, Severin HeinigerFile:Cairns climate.svg Source: http://en.wikipedia.org/w/index.php?title=File:Cairns_climate.svg License: Public Domain Contributors: Fosnez, 1 anonymous editsFile:Atlanta thermal.jpg Source: http://en.wikipedia.org/w/index.php?title=File:Atlanta_thermal.jpg License: Public Domain Contributors: Original uploader was Ryanjo at en.wikipediaFile:Global Warming Map.jpg Source: http://en.wikipedia.org/w/index.php?title=File:Global_Warming_Map.jpg License: unknown Contributors: Reynolds, R.W., N.A. Rayner, T.M. Smith,D.C. Stokes, and W. WangFile:Sturmfront auf Doppler-Radar-Schirm.jpg Source: http://en.wikipedia.org/w/index.php?title=File:Sturmfront_auf_Doppler-Radar-Schirm.jpg License: Public Domain Contributors:A.Fiebig, Pierre cb, Saperaud, Stonda, Tony WillsFile:Origins of acid rain.svg Source: http://en.wikipedia.org/w/index.php?title=File:Origins_of_acid_rain.svg License: Public Domain Contributors: Origins.gif: Original uploader wasNHSavage at en.wikipedia derivative work: Zazou (talk)File:World Koppen Map.png Source: http://en.wikipedia.org/w/index.php?title=File:World_Koppen_Map.png License: Creative Commons Attribution-Sharealike 3.0 Contributors: Peel, M.C., Finlayson, B. L., and McMahon, T. A.(University of Melbourne)File:250mm Rain Gauge.jpg Source: http://en.wikipedia.org/w/index.php?title=File:250mm_Rain_Gauge.jpg License: Creative Commons Attribution 3.0 Contributors: BidgeeFile:Radar-accumulations eng.png Source: http://en.wikipedia.org/w/index.php?title=File:Radar-accumulations_eng.png License: Copyrighted free use Contributors: Pierre cb, Tony Wills, 1anonymous editsfile:1988 US Rain.ogv Source: http://en.wikipedia.org/w/index.php?title=File:1988_US_Rain.ogv License: Public Domain Contributors: NASA/Goddard Space Flight Centerfile:1993 US Rain.ogv Source: http://en.wikipedia.org/w/index.php?title=File:1993_US_Rain.ogv License: Public Domain Contributors: NASA/Goddard Space Flight CenterFile:Rita5dayqpf.gif Source: http://en.wikipedia.org/w/index.php?title=File:Rita5dayqpf.gif License: unknown Contributors: Monkeybait, ThegreatdrFile:deserts.png Source: http://en.wikipedia.org/w/index.php?title=File:Deserts.png License: Public Domain Contributors: Original uploader was Emilfaro at en.wikipedia. Later version(s)were uploaded by Spudtater at en.wikipedia.File:MeanMonthlyP.gif Source: http://en.wikipedia.org/w/index.php?title=File:MeanMonthlyP.gif License: Creative Commons Attribution-Sharealike 3.0 Contributors: PZmaps

License 18

LicenseCreative Commons Attribution-Share Alike 3.0 Unported//creativecommons.org/licenses/by-sa/3.0/

RainFormationWater-saturated airCoalescence

CausesFrontal activityConvectionOrographic effectsWithin the tropicsHuman influence

CharacteristicsPatternsAcidityKppen climate classification

MeasurementGaugesRemote sensingIntensityReturn period

ForecastingImpactEffect on agricultureIn culture

Global climatologyDesertsPolar desertRainforestsMonsoonsImpact of the WesterliesWettest known locations

Outside of EarthNotesReferencesExternal links

License