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A rain shaft at the base of a thunderstorm
Rain is liquid precipitation, as opposed to other kinds of precipitation such as snow, hail and sleet. .On Earth, it is the condensation of atmospheric water vapor into drops of water heavy enough to fall, often making it to the surface.^ Contrary to what is suggested in the popular media, it is water that is the most important greenhouse gas in Earth's atmosphere, not the small amount of demonized CO 2 ...

.Two processes, possibly acting together, can lead to air becoming saturated leading to rainfall: cooling the air or adding water vapour to the air.^ More over, a consensus among the countries, which are affected by the climate change, becomes essential for a pragmatic culmination of the negotiation process that is leading to the final round of climate change negotiation in the forthcoming Copenhagen summit .

Virga is precipitation that begins falling to the earth but evaporates before reaching the surface; it is one of the ways air can become saturated. Precipitation forms via collision with other rain drops or ice crystals within a cloud. .Rain drops range in size from oblate, pancake-like shapes for larger drops, to small spheres for smaller drops.^ It was not like our soft English rain that drops gently on the earth; it was unmerciful and somehow terrible; you felt in it the malignancy of the primitive powers of nature.

Unpolluted rainfall has a pH level of 5.2, making it slightly acidic.
Moisture overriding associated with weather fronts is an overall major method of rain production. If enough moisture and upward motion is present, precipitation falls from convective clouds such as cumulonimbus and can organize into narrow rainbands. In mountainous areas, heavy precipitation is possible where upslope flow is maximized within windward sides of the terrain at elevation. .On the leeward side of mountains, desert climates can exist due to the dry air caused by compressional heating.^ But this episode is generating more heat than light and is likely to lead to more public confusion over the causes of climate change .

The movement of the monsoon trough, or intertropical convergence zone, brings rainy seasons to savannah climes. .Rain is the primary source of fresh water for most areas of the world, providing suitable conditions for diverse ecosystems, as well as water for hydroelectric power plants and crop irrigation.^ Wind, water and solar technologies can provide 100 % of the world ' s energy by 2030, using only technologies that work or are close to working today on a large scale ...

The METAR code for rain is RA. Rainfall is measured through the use of rain gages. Rainfall amounts are estimated actively by weather radar and passively by weather satellites.
Part of the Nature series on
Spring · Summer
Drizzle · Rain  · Snow · Graupel
Freezing rain · Ice pellets · Hail
Weather Portal
The urban heat island effect leads to increased rainfall, both in amounts and intensity, downwind of cities. .Global warming is also causing changes in the precipitation pattern globally, including wetter conditions across eastern North America and drier conditions in the tropics.^ Volcanoes cause global warming or cause global cooling?

^ When the circulation changed so that the North got cooler, the South got warmer, and vice versa — a far cry from the current warming all around the globe.
  • Ocean Currents and Climate 10 February 2010 13:31 UTC [Source type: FILTERED WITH BAYES]

^ Peru's mountain people 'face extinction because of increasingly cold conditions' -- cold blamed on global warming!?

.Precipitation is a major component of the water cycle, and is responsible for depositing most of the fresh water on the planet.^ Black carbon wasn't even listed as a warming agent in the most recent report from the IPCC, but it may be responsible for almost one fifth of the planet ' s warming ...

The globally-averaged annual precipitation is 990 millimetres (39 in). .Climate classification systems such as the Köppen climate classification system use average annual rainfall to help differentiate between differing climate regimes.^ In a new report, scientists used seven different climate models to assess the influence of human induced land cover change on climate.

^ Obama's deal 'nothing short of climate change skepticism in action' -- 'Obama has eliminated any difference between him and Bush' .

Australia is the Earth's driest continent. Rain is also known or suspected on other worlds. On Titan, Saturn's largest moon, infrequent methane rain is thought to carve the moon's numerous surface channels. On Venus, sulfuric acid virga evaporates 25 km from the surface. There is likely to be rain of various compositions in the upper atmospheres of the gas giants, as well as precipitation of liquid neon and helium in the deep atmospheres.


How air becomes saturated

Late-summer rainstorm in Denmark
Air contains water vapour, measured in grams of water per kilogram of dry air (g/kg),[1] but most commonly reported as a relative humidity. How much water vapour a parcel of air can contain before it becomes saturated (100% relative humidity) depends on its temperature. .Warmer air can contain more water vapour than cooler air before becoming saturated.^ They noted that a warmer ocean would tend to evaporate more of its carbon dioxide gas ( CO 2 ) and also water vapor into the air, whereas a colder ocean would tend to absorb both gases.
  • Ocean Currents and Climate 10 February 2010 13:31 UTC [Source type: FILTERED WITH BAYES]

Therefore, one way to saturate a parcel of air is to cool it. The dew point is the temperature to which a parcel must be cooled in order to become saturated.[2] Water vapour normally begins to condense on condensation nuclei such as dust, ice, and salt in order to form clouds. An elevated portion of a frontal zone forces broad areas of lift, which form clouds decks such as altostratus or cirrostratus. .Stratus is a stable cloud deck which tends to form when a cool, stable air mass is trapped underneath a warm air mass.^ Applications of the Precautionary Principle tend to rest on the premise that global warming is more dangerous, or more to be feared, than global cooling.

It can also form due to the lifting of advection fog during breezy conditions.[3]
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.[4] 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,[5] usually by being blown from one surface to another, for example from a liquid water surface to colder land.^ UK Hadley Center: 'I don't think anybody is surprised that we're going to get one model that suggests it's going to cool and another that suggests it's going to warm' .

^ Water takes longer to heat up and does not cool off as easily as land ...

Radiational cooling occurs due to the emission of infrared radiation, either by the air or by the surface underneath.[6] Evaporative cooling occurs when moisture is added to the air through evaporation, which forces the air temperature to cool to its wet-bulb temperature, or until it reaches saturation.[7]
.The main ways water vapour is added to the air are: wind convergence into areas of upward motion,[8] precipitation or virga falling from above,[9] daytime heating evaporating water from the surface of oceans, water bodies or wet land,[10] transpiration from plants,[11] cool or dry air moving over warmer water,[12] and lifting air over mountains.^ They saw that the vast mass of water that gradually creeps northward near the surface of the Atlantic is as important in carrying heat as the familiar and visible Gulf Stream.
  • Ocean Currents and Climate 10 February 2010 13:31 UTC [Source type: FILTERED WITH BAYES]

^ Perhaps in earlier geological eras when the poles had been warmer, salty ocean waters had plunged in the tropics and come up near the poles.
  • Ocean Currents and Climate 10 February 2010 13:31 UTC [Source type: FILTERED WITH BAYES]

^ Arctic melting will release huge quantities of fresh water flowing into the Arctic Ocean.



Raindrops are not tear-shaped. Very small raindrops are nearly spherical As raindrops increase in size, they become flattened at the bottom due to air resistance. The largest raindrops split into smaller raindrops due to air resistance.
Coalescence occurs when water droplets fuse to create larger water droplets, or when water droplets freeze onto an ice crystal, which is known as the Bergeron process. Air resistance typically causes the water droplets in a cloud to remain 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 to overcome air resistance and fall as rain. .Coalescence generally happens most often in clouds above freezing, and is also known as the warm rain process.^ The Paleocene Eocene Thermal Maximum is one of the most dramatic bouts of global warming known to science .

[14] In clouds below freezing, when ice crystals gain enough mass they begin to fall. .This generally requires more mass than coalescence when occurring between the crystal and neighboring water droplets.^ Perhaps it was a slow sloshing of water masses that had made temperatures there, more than in many other regions, rise so noticeably until the 1940s, then dip until the 1970s ( link from above ).
  • Ocean Currents and Climate 10 February 2010 13:31 UTC [Source type: FILTERED WITH BAYES]

This process is temperature dependent, as supercooled water droplets only exist in a cloud that is below freezing. .In addition, because of the great temperature difference between cloud and ground level, these ice crystals may melt as they fall and become rain.^ Why was there an ice age in the Late Ordovician Period, when greenhouse gas levels were nearly 12 times higher then they are today ?

^ The models gave reasonably correct pictures of how sea temperatures changed when perturbed by a great volcanic eruption or even an ice age.
  • Ocean Currents and Climate 10 February 2010 13:31 UTC [Source type: FILTERED WITH BAYES]

^ You know what these natives are, they`re quite capable of storing it where the rain will beat in on it all the time."

Raindrops have sizes ranging from 0.1 millimetres (0.0039 in) to 9 millimetres (0.35 in) mean diameter, above which they tend to break up. Smaller drops are called cloud droplets, and their shape is spherical. As a raindrop increases in size, its shape becomes more oblate, with its largest cross-section facing the oncoming airflow. .Large rain drops become increasingly flattened on the bottom, like hamburger buns; very large ones are shaped like parachutes.^ It was not like our soft English rain that drops gently on the earth; it was unmerciful and somehow terrible; you felt in it the malignancy of the primitive powers of nature.

[16] Contrary to popular belief, their shape does not resemble a teardrop.[17] The biggest raindrops on Earth were recorded over Brazil and the Marshall Islands in 2004 — some of them were as large as 10 mm. The large size is explained by condensation on large smoke particles or by collisions between drops in small regions with particularly high content of liquid water.[18]
Intensity and duration of rainfall are usually inversely related, i.e., high intensity storms are likely to be of short duration and low intensity storms can have a long duration.[19][20] Rain drops associated with melting hail tend to be larger than other rain drops.[21] Raindrops impact at their terminal velocity, which is greater for larger drops due to their larger mass. At sea level and without wind, 0.5 mm drizzle impacts at about 2 m/s, while large 5 mm drops impact at around 9 m/s.[22] The sound of raindrops hitting water is caused by bubbles of air oscillating underwater. The METAR code for rain is RA, while the coding for rain showers is SHRA.[23]


Rainfall with low pH levels, or acid rain, is also a frequent risk produced by lightning within thunderstorms. .Distilled water, which contains no carbon dioxide, has a neutral pH of 7. Liquids with a pH less than 7 are acidic, and those with a pH greater than 7 are bases.^ Carbon-dioxide emissions are turning the waters of the Arctic Ocean into acid at an unprecedented rate, scientists have discovered.

^ No Rise of Atmospheric Carbon Dioxide Fraction in Past 160 Years, New Research Finds .

“Clean” or unpolluted rain has a slightly acidic pH of about .5.2, because carbon dioxide and water in the air react together to form carbonic acid, a weak acid (pH 5.6 in distilled water), but unpolluted rain also contains other chemicals.^ They noted that a warmer ocean would tend to evaporate more of its carbon dioxide gas ( CO 2 ) and also water vapor into the air, whereas a colder ocean would tend to absorb both gases.
  • Ocean Currents and Climate 10 February 2010 13:31 UTC [Source type: FILTERED WITH BAYES]

^ Other groups using carbon-14 data agreed that on average the ocean waters took at least several hundred years to turn over.
  • Ocean Currents and Climate 10 February 2010 13:31 UTC [Source type: FILTERED WITH BAYES]

^ Carbon-dioxide emissions are turning the waters of the Arctic Ocean into acid at an unprecedented rate, scientists have discovered.

[24] Nitrous oxide present during thunderstorm phenomena,[25] caused by the splitting of nitrogen molecules, can result in the production of acid rain, if nitrous oxide forms compounds with the water molecules in precipitation, thus creating acid rain. Acid rain can damage buildings and other external structures. .In ecosystems, acid rain can dissolve plant tissues of vegetation and increase acidification process in soil and bodies of water,[26] resulting in deaths of marine organisms.^ The acid might eventually dissolve the calcium-carbonate shells of plankton and other creatures important in marine food chains, with uncertain effects on seawater chemistry.
  • Ocean Currents and Climate 10 February 2010 13:31 UTC [Source type: FILTERED WITH BAYES]



Frontal activity

Stratiform or dynamic precipitation occurs as a consequence of slow ascent of air in synoptic systems (on the order of cm/s), such as over surface cold fronts, and over and ahead of warm fronts. Similar ascent is seen around tropical cyclones outside of the eyewall, and in comma-head precipitation patterns around mid-latitude cyclones.[28] A wide variety of weather can be found along an occluded 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.[29]


Convective precipitation
Convective rain, or showery precipitation, occurs from convective clouds, e.g., cumulonimbus or cumulus congestus. It falls as showers with rapidly changing intensity. Convective precipitation falls over a certain area for a relatively short time, as convective clouds have limited horizontal extent. Most precipitation in the tropics appears to be convective; however, it has been suggested that stratiform precipitation also occurs.[28][30] Graupel and hail indicate convection.[31] In mid-latitudes, convective precipitation is intermittent and often associated with baroclinic boundaries such as cold fronts, squall lines, and warm fronts.[32]

Orographic effects

Orographic precipitation
Orographic precipitation occurs on the windward side of mountains and is caused by the rising air motion of a large-scale flow of moist air across the mountain ridge, resulting in adiabatic cooling and condensation. .In mountainous parts of the world subjected to relatively consistent winds (for example, the trade winds), a more moist climate usually prevails on the windward side of a mountain than on the leeward or downwind side.^ Climate Scare Fading: 'More Americans believe in haunted houses than man-made global warming' - 37% vs. .

^ Provision 'declares a climate emergency if world greenhouse gas levels climb above 450 parts per million' .

^ Warming Establishment Crumbles: More than 140 scientists challenge UN's climate claims in open letter .

Moisture is removed by orographic lift, leaving drier air (see katabatic wind) on the descending and generally warming, leeward side where a rain shadow is observed.[13]
.In Hawaii, Mount Waiʻaleʻale, on the island of Kauai, is notable for its extreme rainfall, as it has the second highest average annual rainfall on Earth, with 460 inches (12,000 mm).^ Ice-cores reveal that Mount Kilimanjaro has been covered in glaciers for almost 12,000 years.

[33] Systems known as Kona storms affect the state with heavy rains between October and April.[34] Local climates vary considerably on each island due to their topography, divisible into windward (Koʻolau) and leeward (Kona) regions based upon location relative to the higher mountains. Windward sides face the east to northeast trade winds and receive much more rainfall; leeward sides are drier and sunnier, with less rain and less cloud cover.[35]
In South America, the Andes mountain range blocks Pacific moisture that arrives in that continent, resulting in a desertlike climate just downwind across western Argentina.[36] The Sierra Nevada range creates the same effect in North America forming the Great Basin and Mojave Deserts.[37][38]

Within the tropics

Rainfall distribution by month in Cairns showing the extent of the wet season at that location
.The wet, or rainy, season is the time of year, covering one or more months, when most of the average annual rainfall in a region falls.^ One more headache: When the drop down menues partially cover an icon, they erase that portion of the icon.
  • - themes: themes/rain 16 January 2010 19:19 UTC [Source type: General]

^ Submitted by: Dan Thursday September 18th 2003 To answer my own question @77, I tried one more time and got in with no problem.
  • - themes: themes/rain 16 January 2010 19:19 UTC [Source type: General]

^ One of the largest glaciers in Antarctica is now thinning four times faster than it was ten years ago.

[39] The term green season is also sometimes used as a euphemism by tourist authorities.[40] Areas with wet seasons are dispersed across portions of the tropics and subtropics.[41] Savanna climates and areas with monsoon regimes have wet summers and dry winters. Tropical rainforests technically do not have dry or wet seasons, since their rainfall is equally distributed through the year.[42] Some areas with pronounced rainy seasons will see a break in rainfall mid-season when the intertropical convergence zone or monsoon trough move poleward of their location during the middle of the warm season.[19] When the wet season occurs during the warm season, or summer, rain falls mainly during the late afternoon and early evening hours. The wet season is a time when air quality improves,[43] freshwater quality improves,[44][45] and vegetation grows significantly.
Tropical cyclones, a source of very heavy rainfall, consist of large air masses several hundred miles across with low pressure at the centre and with winds blowing inward towards the centre in either a clockwise direction (southern hemisphere) or counterclockwise (northern hemisphere).[46] .Although cyclones can take an enormous toll in lives and personal property, they may be important factors in the precipitation regimes of places they impact, as they may bring much-needed precipitation to otherwise dry regions.^ But I think, sidebar tab headers and browser tabs are too high, they take up too much of window space.
  • - themes: themes/rain 16 January 2010 19:19 UTC [Source type: General]

^ There are one or two traders, of course, but we take care to make them behave, and if they don`t we make the place so hot for them they`re glad to go."

[47] Areas in their path can receive a year's worth of rainfall from a tropical cyclone passage.[48]

Human influence

Image of Atlanta, Georgia showing temperature distribution, with blue showing cool temperatures, red warm, and hot areas appear white.
The fine particulate matter produced by car exhaust and other human sources of pollution forms cloud condensation nuclei, leads to the production of clouds and increases the likelihood of rain. As commuters and commercial traffic cause pollution to build up over the course of the week, the likelihood of rain increases: it peaks by Saturday, after five days of weekday pollution has been built up. In heavily populated areas that are near the coast, such as the United States' Eastern Seaboard, the effect can be dramatic: there is a 22% higher chance of rain on Saturdays than on Mondays.[49] The urban heat island effect warms cities 0.6 °C (1.1 °F) to 5.6 °C (10.1 °F) above surrounding suburbs and rural areas. This extra heat leads to greater upward motion, which can induce additional shower and thunderstorm activity. Rainfall rates downwind of cities are increased between 48% and 116%. .Partly as a result of this warming, monthly rainfall is about 28% greater between 20 miles (32 km) to 40 miles (64 km) downwind of cities, compared with upwind.^ Global warming theory 'is falling to bits': '2 recent results published by top scientists cast doubt on the UN IPCC's theory about link between atmospheric CO2 and global warming' .

[50] Some cities induce a total precipitation increase of 51%.[51]
Mean surface temperature anomalies during the period 1999 to 2008 with respect to the average temperatures from 1940 to 1980
Increasing temperatures tend to increase evaporation which leads to more precipitation. .As average global temperatures have risen, average global precipitation has also increased.^ Scientists 'puzzled as to why average global temperatures have stopped rising over the last 10 years' .

^ Update: NOAA removes web page stating 'There is no evidence that CO2 is causing an increase in global temperatures' .

^ NOAA's website: Promotes climate discussion by stating: 'There is no evidence that CO2 is causing an increase in global temperatures' .

Precipitation generally increased over land north of 30°N from 1900 through 2005 but has declined over the tropics since the 1970s. .Globally there has been no statistically significant overall trend in precipitation over the past century, although trends have varied widely by region and over time.^ Poll: Half of UK public believes there is no proof global warming caused by humans .

^ Equally significant was the time scale, which turned out to be half a millennium or so (in particular, the deep water of the North Atlantic had been down there an average of 650 years).
  • Ocean Currents and Climate 10 February 2010 13:31 UTC [Source type: FILTERED WITH BAYES]

^ Analysis: 3 of 4 measurements show no significant global warming for the last 15 years .

.Eastern portions of North and South America, northern Europe, and northern and central Asia have become wetter.^ The previous winter had been phenomenally cold and snowy in North America and Europe.
  • Ocean Currents and Climate 10 February 2010 13:31 UTC [Source type: FILTERED WITH BAYES]

The Sahel, the Mediterranean, southern Africa and parts of southern Asia have become drier. .There has been an increase in the number of heavy precipitation events over many areas during the past century, as well as an increase since the 1970s in the prevalence of droughts—especially in the tropics and subtropics.^ 'Airborne fraction of carbon dioxide has not increased either during the past 150 years or during the most recent 5 decades' .

^ It was just one of a number of studies that led to the recognition, in the 1970s, that there were ocean-atmosphere feedback oscillations on a timescale of a few years to a few decades.
  • Ocean Currents and Climate 10 February 2010 13:31 UTC [Source type: FILTERED WITH BAYES]

.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 less precipitation and/or more evaporation).^ These studies were no more than suggestive, for the models of the mid 1980s were still extremely limited.
  • Ocean Currents and Climate 10 February 2010 13:31 UTC [Source type: FILTERED WITH BAYES]

^ The upper ocean layers also seemed to mix together more in regions with many storms, and storminess was another thing that might change as the climate changed.
  • Ocean Currents and Climate 10 February 2010 13:31 UTC [Source type: FILTERED WITH BAYES]

^ Perhaps, he thought, there had been a transition in the ocean from "a relatively stagnant state" to a state where more rapid mixing brought nutrients to the surface which changed the biochemistry.
  • Ocean Currents and Climate 10 February 2010 13:31 UTC [Source type: FILTERED WITH BAYES]

.Over the contiguous United States, total annual precipitation increased at an average rate of 6.1 percent per century since 1900, with the greatest increases within the East North Central climate region (11.6 percent per century) and the South (11.1 percent).^ Yet it seemed at least an "intriguing possibility," as they put it, that global warming might shut down the North Atlantic circulation within the next century or so, with grave implications for regional climates.
  • Ocean Currents and Climate 10 February 2010 13:31 UTC [Source type: FILTERED WITH BAYES]

^ Monbiot: 'The emails extracted by a hacker from the climatic research unit at the University of East Anglia could scarcely be more damaging' .

^ A few worried that the North Atlantic region was precisely where most of the data on abrupt climate change came from, and where most of the people who thought about it lived.
  • Ocean Currents and Climate 10 February 2010 13:31 UTC [Source type: FILTERED WITH BAYES]

Hawaii was the only region to show a decrease (-9.25 percent).[52]


Band of thunderstorms seen on a weather radar display
Rainbands are cloud and precipitation areas which are significantly elongated. Rainbands can be stratiform or convective,[53] and are generated by differences in temperature. When noted on weather radar imagery, this precipitation elongation is referred to as banded structure.[54] Rainbands in advance of warm occluded fronts and warm fronts are associated with weak upward motion,[55] and tend to be wide and stratiform in nature.[56]
Rainbands spawned near and ahead of cold fronts can be squall lines which are able to produce tornadoes.[57] Rainbands associated with cold fronts can be warped by mountain barriers perpendicular to the front's orientation due to the formation of a low-level barrier jet.[58] Bands of thunderstorms can form with sea breeze and land breeze boundaries, if enough moisture is present. If sea breeze rainbands become active enough just ahead of a cold front, they can mask the location of the cold front itself.[59] Banding within the comma head precipitation pattern of an extratropical cyclone can yield significant amounts of rain.[60] Behind extratropical cyclones, rainbands can form downwind of relative warm bodies of water such as the Great Lakes. Downwind of islands, bands of showers and thunderstorms can develop due to low level wind convergence downwind of the island edges. Offshore California, this has been noted in the wake of cold fronts.[61]
Rainbands within tropical cyclones are curved in orientation. Tropical cyclone rainbands contain showers and thunderstorms that, together with the eyewall and the eye, constitute a hurricane or tropical storm. The extent of rainbands around a tropical cyclone can help determine the cyclone's intensity.[62]



Standard rain gauge
The standard way of measuring rainfall or snowfall is the standard rain gauge, which can be found in 100-mm (4-in) plastic and 200-mm (8-in) metal varieties.[63] The inner cylinder is filled by 25 mm (1 in) of rain, with overflow flowing into the outer cylinder. Plastic gages have markings on the inner cylinder down to 0.25 mm (0.01 in) resolution, while metal gauges require use of a stick designed with the appropriate 0.25 mm (0.01 in) markings. After the inner cylinder is filled, the amount inside it is discarded, then filled with the remaining rainfall in the outer cylinder until all the fluid in the outer cylinder is gone, adding to the overall total until the outer cylinder is empty.[64] Other types of gauges include the popular wedge gauge (the cheapest rain gauge and most fragile), the tipping bucket rain gauge, and the weighing rain gauge.[65] .For those looking to measure rainfall the most inexpensively, a can that is cylindrical with straight sides will act as a rain gauge if left out in the open, but its accuracy will depend on what ruler you use to measure the rain with.^ Answer is no : classic use OS X aqua ruler but every other theme I tried based on it got the same bug as "Rain".
  • - themes: themes/rain 16 January 2010 19:19 UTC [Source type: General]

Any of the above rain gauges can be made at home, with enough know-how.[66]
.When a precipitation measurement is made, various networks exist across the United States and elsewhere where rainfall measurements can be submitted through the Internet, such as CoCoRAHS or GLOBE.[67][68] If a network is not available in the area where one lives, the nearest local weather office will likely be interested in the measurement.^ "In weather like this a native hut must be a rather uncomfortable place to live in."


Remote sensing

Twenty-four hour rainfall accumulation on the Val d'Irène radar in Eastern Canada. Zones without data in the 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 the amount of precipitations fallen over large basins for hydrological purposes.[70] For instance, river flood control, sewer management and dam construction are all areas where planners use rainfall accumulation data. Radar-derived rainfall estimates compliment surface station data which can be used for calibration. To produce radar accumulations, rain rates over a point are estimated by using the value of reflectivity data at individual grid points. A radar equation is then used, which is,
Z = ARb,
where Z represents the radar reflectivity, R represents the rainfall rate, and A and b are constants.[71] Satellite derived rainfall estimates use passive microwave instruments aboard polar orbiting as well as geostationary weather satellites to indirectly measure rainfall rates.[72] .If one wants for a accumulate rainfall over a time period, one has to add up all the accumulations from each grid box within the images during that time.^ For Want of Water: Quenching Las Vegas' Thirst Desert dwellers find summer sizzle, little rainfall Desert oasis drying up Las Vegas weather can be a gamble .
  • Current Weather Conditions - Las Vegas Sun 17 January 2010 8:29 UTC [Source type: Reference]

^ The notification box shows up where it should, when it should, but there is no image in it.
  • - themes: themes/rain 16 January 2010 19:19 UTC [Source type: General]

^ Vermont sets 'all-time record for one snowstorm' .


Rainfall intensity is classified according to the rate of precipitation:
  • Light rain — when the precipitation rate is < 2.5 millimetres (0.098 in) per hour
  • Moderate rain — when the precipitation rate is between 2.5 millimetres (0.098 in) - 7.6 millimetres (0.30 in) per hour
  • Heavy rain — when the precipitation rate is > 7.6 millimetres (0.30 in) per hour[73]

Return period

The likelihood or probability of an event with a specified intensity and duration, is called the return period or frequency.[74] The intensity of a storm can be predicted for any return period and storm duration, from charts based on historic data for the location.[75] .The term 1 in 10 year storm describes a rainfall event which is rare and is only likely to occur once every 10 years, so it has a 10 percent likelihood any given year.^ National Weather Service records showed that snowfall that sticks around in the valley occurs on average every 20 years.
  • Current Weather Conditions - Las Vegas Sun 17 January 2010 8:29 UTC [Source type: Reference]

.The rainfall will be greater and the flooding will be worse than the worst storm expected in any single year.^ 'Oceans have a much greater capacity to absorb CO2 than had been previously expected' .

The term 1 in 100 year storm describes a rainfall event which is extremely rare and which will occur with a likelihood of only once in a century, so has a 1 percent likelihood in any given year. .The rainfall will be extreme and flooding to be worse than a 1 in 10 year event.^ 'Gore can't tell time – thinks most recent Climategate email is more than 10 years old' .

As with all probability events, it is possible to have multiple "1 in 100 Year Storms" in a single year.[76]

Effect on agriculture

Rainfall estimates for southern Japan and the surrounding region from July 20–27, 2009.
Precipitation, 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 is usually vital to healthy plants, too much or too little rainfall can be harmful, even devastating to crops. Drought can kill crops and increase erosion,[77] while overly wet weather can cause harmful fungus growth.[78] Plants need varying amounts of rainfall to survive. .For example, certain cacti require small amounts of water,[79] while tropical plants may need up to hundreds of inches of rain per year to survive.^ We have three hundred inches in the year.

^ UN climate treaty may need extra year .

^ 'Hundreds of tiny LEDs that light up, depending on the amount of CO2 in the air' .

In areas with wet and dry seasons, soil nutrients diminish and erosion increases during the wet season.[19] Animals have adaptation and survival strategies for the wetter regime. The previous dry season leads to food shortages into the wet season, as the crops have yet to mature.[80] Developing countries have noted that their populations show seasonal weight fluctuations due to food shortages seen before the first harvest, which occurs late in the wet season.[81] Rain may be harvested through the use of rainwater tanks or for non-potable use indoors or for irrigation,[82] as a form of greywater. Excessive rain during short periods of time can cause flash floods.[83]


Cultural attitudes towards rain differ across the world. .In temperate climates, people tend to be more stressed when the weather is unstable or cloudy, with its impact greater on men than women.^ Climate Scare Fading: 'More Americans believe in haunted houses than man-made global warming' - 37% vs. .

^ Warming Establishment Crumbles: More than 140 scientists challenge UN's climate claims in open letter .

^ Climate of Change: Gore speech draws more than 200 protesters in Florida -- 'Boos and chants could be heard' during talk .

[84] Rain can also bring joy, as some consider it to be soothing or enjoy the aesthetic appeal of it. In dry places, such as India,[85] or during periods of drought,[86] rain lifts people's moods. In Botswana, the Setswana word for rain, "pula," is used as the name of the national currency, in recognition of the economic importance of rain in this desert country.[87] .Several cultures have developed means of dealing with rain and have developed numerous protection devices such as umbrellas and raincoats, and diversion devices such as gutters and storm drains that lead rains to sewers.^ Asian Development Bank warns failure to 'reach climate deal could lead to a collapse of carbon market' .

[88] Many people find the scent during and immediately after rain pleasant or distinctive. The source of this scent is petrichor, an oil produced by plants, then absorbed by rocks and soil, and later released into the air during rainfall.[89]


Example of a five day rainfall forecast from the Hydrometeorological Prediction Center
The Quantitative Precipitation Forecast (abbreviated QPF) is the expected amount of liquid precipitation accumulated over a specified time period over a specified area.[90] A QPF will be specified when a measurable precipitation type reaching a minimum threshold is forecast for any hour during a QPF valid period. Precipitation forecasts tend to be bound by synoptic hours such as 0000, 0600, 1200 and 1800 GMT. Terrain is considered in QPFs by use of topography or based upon climatological precipitation patterns from observations with fine detail.[91] Starting in the mid to late 1990s, QPFs were used within hydrologic forecast models to simulate impact to rivers throughout the United States.[92] Forecast models show significant sensitivity to humidity levels within the planetary boundary layer, or in the lowest levels of the atmosphere, which decreases with height.[93] QPF can be generated on a quantitative, forecasting amounts, or a qualitative, forecasting the probability of a specific amount, basis.[94] .Radar imagery forecasting techniques show higher skill than model forecasts within 6 to 7 hours of the time of the radar image.^ Peer-Research Determines Gulf of Mexico Medieval Warming Had Higher Temperatures Than Modern Times .

The forecasts can be verified through use of rain gage measurements, weather radar estimates, or a combination of both. Various skill scores can be determined to measure the value of the rainfall forecast.[95]

Role in Köppen climate classification

Updated Köppen-Geiger climate map[96]
     Af      Am      Aw      BWh      BWk      BSh      BSk      Csa      Csb      Cwa      Cwb      Cfa      Cfb      Cfc      Dsa      Dsb      Dsc      Dsd      Dwa      Dwb      Dwc      Dwd      Dfa      Dfb      Dfc      Dfd      ET      EF
The Köppen classification depends on average monthly values of temperature and precipitation. The most commonly used form of the Köppen classification has five primary types labeled A through E. Specifically, the primary types are A, tropical; B, dry; C, mild mid-latitude; D, cold mid-latitude; and E, polar. The five primary classifications can be further divided into secondary classifications such as rain forest, monsoon, tropical savanna, humid subtropical, humid continental, oceanic climate, Mediterranean climate, 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 millimetres (69 in) and 2,000 millimetres (79 in).[97] .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 millimetres (30 in) and 1,270 millimetres (50 in) a year.^ Peer-reviewed study shakes climate debate: '50 years of global cooling predicted' -- Finds CO2 NOT 'major culprit' in temps .

They are widespread on Africa, and are also found in India, the northern parts of South America, Malaysia, and Australia.[98] The humid subtropical climate zone where winter rainfall (and sometimes snowfall) is associated with large storms that the westerlies steer from west to east. Most summer rainfall occurs during thunderstorms and from occasional tropical cyclones.[99] Humid subtropical climates lie on the east side continents, roughly between latitudes 20° and 40° degrees away from the equator.[100]
An oceanic (or maritime) climate is typically found along the west coasts at the middle latitudes of all the world's continents, bordering cool oceans, as well as southeastern Australia, and is accompanied by plentiful precipitation year round.[101] 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 of central Chile. The climate is characterized by hot, dry summers and cool, wet winters.[102] A steppe is a dry grassland.[103] .Subarctic climates are cold with continuous permafrost and little precipitation.^ Chris Mooney: 'The Continuing, Unfortunate Effectiveness of Climate Depot's Morano...a leading nemesis of climate progress...there is, in my mind, little effective counter' .

^ Climate Depot Exclusive - Continuously Updated 'ClimateGate' News Round Up Obama Spokesman Gibbs Blames Record Cold On Global Warming!


Global climatology

Approximately 505,000 cubic kilometres (121,000 cu mi) of water falls as precipitation each year across the globe with 398,000 cubic kilometres (95,000 cu mi) of it over the oceans.[105] .Given the Earth's surface area, that means the globally-averaged annual precipitation is 990 millimetres (39 in).^ Plus: 'Global-average sea surface temps in October continued fall from peak in July, despite El Nino conditions' .

.Deserts are defined as areas with an average annual precipitation of less than 250 millimetres (10 in) per year,[106][107] or as areas where more water is lost by evapotranspiration than falls as precipitation.^ Scientists 'puzzled as to why average global temperatures have stopped rising over the last 10 years' .

^ Aussie Scientist: 'More evidence CO2 not culprit -- 'Climate sensitivity associated with CO2 is less than that used in present climate modelling, by a factor of about 3' .

^ 'Gore can't tell time – thinks most recent Climategate email is more than 10 years old' .



Largest deserts
The northern half of Africa is primarily desert or arid, containing the Sahara. Across Asia, a large annual rainfall minimum, composed primarily of deserts, stretches from the Gobi desert in Mongolia west-southwest through Pakistan and Iran into the Arabian desert in Saudi Arabia. Most of Australia is semi-arid or desert,[109] making it the world's driest continent. In South America, the Andes mountain range blocks Pacific moisture that arrives in that continent, resulting in a desertlike climate just downwind across western Argentina.[36] The drier areas of the United States are regions where the Sonoran desert overspreads the Desert Southwest, the Great Basin, central Wyoming, and the Willamette Valley.[110]


The equatorial region near the Intertropical Convergence Zone (ITCZ), or monsoon trough, is the wettest portion of the world's continents. Annually, the rain belt within the tropics marches northward by August, then moves back southward into the Southern Hemisphere by February and March.[111] Within Asia, rainfall is favored across its southern portion from India east and northeast across the Philippines and southern China into Japan due to the monsoon advecting moisture primarily from the Indian Ocean into the region.[112] The monsoon trough can reach as far north as the 40th parallel in East Asia during August before moving southward thereafter. Its poleward progression is accelerated by the onset of the summer monsoon which is characterized by the development of lower air pressure (a thermal low) over the warmest part of Asia.[113][114][115] Similar, but weaker, monsoon circulations are present over North America and Australia.[116][117] .During the summer, the Southwest monsoon combined with Gulf of California and Gulf of Mexico moisture moving around the subtropical ridge in the Atlantic ocean bring the promise of afternoon and evening thunderstorms to the southern tier of the United States as well as the Great Plains.^ New Peer-Reviewed Research: Atlantic Ocean Was 2.7°C Warmer During Roman Warm Period, 2.2°C Warmer During MWP .

[118] The eastern half of the contiguous United States east of the 98th meridian, the mountains of the Pacific Northwest, and the Sierra Nevada range are the wetter portions of the nation, with average rainfall exceeding 30 inches (760 mm) per year.[110] Equatorward of the subtropical ridge, tropical cyclones enhance precipitation across southern and eastern sections of the United States, as well as Puerto Rico, the United States Virgin Islands,[119] the Northern Mariana Islands,[120] Guam, and American Samoa.

Impact of the Westerlies

Long-term mean precipitation by month
.Westerly flow from the mild north Atlantic leads to wetness across western Europe, in particular the United Kingdom, where the western coasts can receive between 1000 mm (40 in, at sea-level) and 2500 mm (100 in, on the mountains) of rain per year.^ North Carolina Sea Levels Rising 3mm a year?

^ Amusing: North Carolina sea levels rose at the 'wrong' time .

.In Bergen, Norway is one of the more famous European rain-cities with its yearly precipitation of 2250 mm (88 in) on average.^ 'On average each day in 1855 more than 50 tons of horse excrement was removed from only one street' .

During the fall, winter, and spring, Pacific storm systems bring most of Hawaii and the western United States much of their precipitation.[118] Over the top of the ridge, the jet stream brings a summer precipitation maximum to the Great Lakes. .Large thunderstorm areas known as mesoscale convective complexes move through the Plains, Midwest, and Great Lakes during the warm season, contributing up to 10% of the annual precipitation to the region.^ Rush Limbaugh Praises Climate Depot: 'It's a great place to keep up on the global warming debate' .

The El Niño-Southern Oscillation affects the precipitation distribution, by altering rainfall patterns across the western United States,[122] Midwest,[123][124] the Southeast,[125] and throughout the tropics. .There is also evidence that global warming is leading to increased precipitation to the eastern portions of North America, while droughts are becoming more frequent in the tropics and subtropics.^ 'Global warming leads to too many polar bears' .

^ Chinese debate positive side of global warming: 'Dynasties were more prosperous' when weather was warm' .

^ More Data Questions: 'There is at least one temp station where trend has been artificially increased to give a false warming where raw data shows cooling' .

Wettest known locations

.Cherrapunji, situated on the southern slopes of the Eastern Himalaya in Shillong, India is one of the wettest places on Earth, with an average annual rainfall of 11,430 mm (450 in).^ 'A hypocrite as well as a liar': IPCC's Pachauri resides in 'one of the most expensive places to live in India' .

.The highest recorded rainfall in a single year was 22,987 mm (904.9 in) in 1861. The 38-year average at nearby Mawsynram, Meghalaya, India is 11,873 mm (467.4 in).^ National Weather Service records showed that snowfall that sticks around in the valley occurs on average every 20 years.
  • Current Weather Conditions - Las Vegas Sun 17 January 2010 8:29 UTC [Source type: Reference]

[126] .The wettest spot in Australia is Mount Bellenden Ker in the north-east of the country records an average of 8,000 millimetres (310 in) per year, with over 1,200 millimetres (47 in) of rain recorded in the year 2000.[127] Mount Waialeale on the island of Kauaʻi in the Hawaiian Islands averages more than 11,680 millimetres (460 in) of rain over the last 32 years, with a record 17,340 millimetres (683 in) in 1982. Its summit is considered one of the rainiest spots on earth.^ After many years of married life he had learned that it was more conducive to peace to leave his wife with the last word.

^ Developing countries now emit more 'greenhouse gas' than rich countries .

^ Climate of Change: Gore speech draws more than 200 protesters in Florida -- 'Boos and chants could be heard' during talk .

It has been promoted in tourist literature for many years as the wettest spot in the world.[128] Lloró, a town situated in Chocó, Colombia, is probably the place with the largest measured rainfall in the world, averaging 13,300 mm per year (523.6 in).[129] The Department of Chocó is extraordinarily humid. Tutunendo, a small town situated in the same department, is one of the wettest places on earth, averaging 11,394 mm per year (448 in); in 1974 the town received 26,303 mm (86 ft 3½ in), the largest annual rainfall measured in Colombia. Unlike Cherrapunji, which receives most of its rainfall between April and September, Tutunendo receives rain almost uniformly distributed throughout the year.[130] .Quibdó, the capital of Chocó, receives the most rain in the world among cities with over 100,000 inhabitants: 9000 mm (29 ft 6 in) per year.^ 'Takes between 100 to 1,000 years for a golf ball to decompose naturally' -- '300 million balls are lost or discarded in U.S. alone' .

Storms in Chocó can drop 500 mm (19.7 in) of rainfall in a day. .This amount is more than falls in many cities in a year's time.^ After many years of married life he had learned that it was more conducive to peace to leave his wife with the last word.

^ 'Gore can't tell time – thinks most recent Climategate email is more than 10 years old' .

^ Scientist: 'For more than 90% of recent geological time Earth has been colder than today' .

Outside of Earth

On Titan, Saturn's largest moon, infrequent methane rain is thought to carve the moon's numerous surface channels.[131 ] On Venus, sulfuric acid virga evaporates 25 km from the surface. There is likely to be rain of various compositions in the upper atmospheres of the gas giants, as well as precipitation of liquid neon and helium in the deep atmospheres.

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External links

Source material

Up to date as of January 22, 2010

From Wikisource

by Alfred Francis Kreymborg
It's all very well for you
  suddenly to withdraw
  and say, I'll come again,
but what of the bruises you've left,
what of the green and the blue,
  the yellow, purple and violet?--
don't you be telling us,
  I'm innocent of these,
  irresponsible of happenings--
didn't we see you steal next to her,
  with your silver mist about you
  to hide your blandishment?--
now, what of what followed, eh?--
we saw you hover close,
  caress her,
  open her pore-cups,
  make a cross of her,
  quickly penetrate her--
she opening to you,
  engulfing you,
  every limb of her,
  bud of her, pore of her?--
don't call these things, kisses--
  mouth-kisses, hand-kisses,
  elbow, knee and toe,
and let it go at that--
  disappear and promise
  what you'll never perform:
we've known you to slink away
  until drought-time,
we've caught you crawling off
  into winter-time,
  try to cover what you've done
  with a long white scarf—
your own frozen tears
  (likely phrase!)
  and lilt your,
  I'll be back in spring!
Next spring, and you know it,
  she won't be the same,
  though she may look the same
  to you from where you are,
  and invite you down again!
PD-icon.svg This work is in the public domain in the United States because it was published before January 1, 1923.
The author died in 1966, so this work is also in the public domain in countries and areas where the copyright term is the author's life plus 30 years or less. This work may also be in the public domain in countries and areas with longer native copyright terms that apply the rule of the shorter term to foreign works.

1911 encyclopedia

Up to date as of January 14, 2010

From LoveToKnow 1911

'RAIN (O.E.' regn; the word is common to Teutonic languages, cf. Ger. Regen, Swed. and Dan. regn; it has been connected with Lat. rigare, to wet, Gr. .(3pEX€w), the water vapour of the atmosphere when condensed into drops large enough to be precipitated upon the earth.^ In the process, the sun heats large expanses of water, which causes some of the water to evaporate into vapour.
  • 16 January 2010 19:19 UTC [Source type: Original source]

^ Clouds are just big fluffy floating white things up in the sky made up of condensed water vapour 8 .
  • 16 January 2010 19:19 UTC [Source type: Original source]

^ Rain 1 , a type of weather , is droplets of water (chemically H 2 O) that form in the atmosphere from water vapour.
  • 16 January 2010 19:19 UTC [Source type: Original source]

.Hence the term is extended to signify the fall of such drops in a shower, and in the plural, "the rains," it signifies the rainy seasons in India and elsewhere where under normal climatic conditions such seasons are clearly distinguished from the dry.^ When acid rain falls it can be devastating, much like showers of vinegar, and can kill off plant life and leave forests - such as the Black Forest, Germany - in ruin.
  • 16 January 2010 19:19 UTC [Source type: Original source]

^ Moment of Clarity down under: 'Australians care less about climate change -- concern dropped 14% .

^ How can anyone who knows earth history apply such terms to climate today?

A rain-band is "a dark band in the solar spectrum, caused by the presence of water-vapour in the atmosphere" (New Engl. Diet.); a rain-gauge is an instrument used to measure the amount of rainfall (see Meteorology, where the, whole subject of precipitation is fully treated).


Up to date as of January 15, 2010

Definition from Wiktionary, a free dictionary

See also rain, and räin




Short form of Rainer and other Germanic compound given names with the first element meaning "counsel".

Proper noun

  1. A male given name.

Related terms

Bible wiki

Up to date as of January 23, 2010

From BibleWiki

There are three Hebrew words used to denote the rains of different seasons, (1.) Yoreh (Hos 6:3), or moreh (Joel 2:23), denoting the former or the early rain. (2.) Melqosh, the "latter rain" (Prov 16:15). (3.) Geshem, the winter rain, "the rains." .The heavy winter rain is mentioned in Gen 7:12; Ez 10:9; Song 2:11.^ The RAIN Report for 12-11-2009 .

^ The RAIN Report for 11-10-2006 .

^ The RAIN Report for 10-11-2007 .

.The "early" or "former" rains commence in autumn in the latter part of October or beginning of November (Deut 11:14; Joel 2:23; comp.^ The RAIN Report for 11-14-2008 .

^ The RAIN Report for 11-23-2006 .

^ This Week: Part two of "WLS - A Retrospective" with author and former RAIN reader, Scott Childers, W9CHI. (13 minutes) .

Jer 3:3), and continue to fall heavily for two months. Then the heavy "winter rains" fall from the middle of December to March. .There is no prolonged fair weather in Palestine between October and March.^ In the Copenhagen Accord there are no deadlines, no assurances, and talk of keeping below 2C makes no link between science and the reality of continued pollution.

^ THIS WEEK: Due to technical reasons beyond our control there is no RAIN Report for the week of March 13-19.

^ 'It appears from the details of the scandal that there is no relationship whatsoever between human activities and climate change' .

.The "latter" or spring rains fall in March and April, and serve to swell the grain then coming to maturity (Deut 11:14; Hos 6:3).^ The RAIN Report for 11-14-2008 .

.After this there is ordinarily no rain, the sky being bright and cloudless till October or November.^ HURRICANES The official Atlantic hurricane season generally extends from June 1 through November 30, with peaks from mid-August till mid-October.
  • Aruba Weather 17 January 2010 8:29 UTC [Source type: FILTERED WITH BAYES]

^ THIS WEEK: Due to technical reasons beyond our control there is no RAIN Report for the week of March 13-19.

Rain is referred to symbolically in Deut 32:2; Ps 726; Isa 44:3, 4; Hos 10:12.
This entry includes text from Easton's Bible Dictionary, 1897.
what mentions this? (please help by turning references to this page into wiki links)
This article needs to be merged with RAIN (Jewish Encyclopedia).
Facts about RainRDF feed

Simple English

File:22 Regen
Rain falling

Rain are droplets of water falling from clouds in the sky that are bigger than 0.5 mm. Droplets of water that are about 0.2mm to 0.5mm big are called drizzle. Rain is a kind of precipitation. Precipitation is any kind of water that falls from clouds in the sky, like rain, hail, sleet and snow. Rain is part of the water cycle.


Types of rain

Convectional rain

Convectional rain happens in places of the world that are hot and wet. Sometimes, it also takes place in tropical deserts and inland areas during summer, when temperatures are hot. During the day, the sun makes the ground very hot. Air near the ground surface is heated by conduction. The heated air expands, becoming less dense and rises in a strong upwards air current. When the temperature of the rising air falls to the dew point, water vapor shrinks into thick clouds and forms convection rain. Depending on the temperature it may fall as sleet or snow.

Relief rain

Relief rain usually happens along coastal areas where a line of hills runs along to the coast. When wet onshore wind from the sea meets a mountain, hill and barrier, it is forced to rise along the slope and cools. When the air temperature falls to its dew point, water vapor condenses to form clouds. When the clouds can no longer hold the water droplets, relief rain begins to fall on the windward slope of the mountain. On the leeward slope, air sinks, it is warmed and further dried by compression. Therefore, the leeward slope is known as rain shadow. Moist winds blow in from the sea and are forced to rise over the land. The air cools and the water vapour condenses, forming rain drops. Relief rain is also a very dense and cold mixture of precipitation.

Frontal rain/Cyclonic rain

Frontal rain is when a cold front meets a warm air front. The less dense warm air rises and condenses forming clouds. These clouds get heavier and it eventually rains. The cold air front tends to come from the north west and the warm air front comes from the south west.


A Rainstorm is a sudden heavy fall of rain. It may cause floods on land which is not much above the level of the sea for example, flat coastal land and river basins. Too much water can make rivers overflow and cause floods. Also, landslides may happen. This is bad news as people may drown. For example, over 6 million people died just last year from rainstorms.

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Citable sentences

Up to date as of December 29, 2010

Here are sentences from other pages on Climate, which are similar to those in the above article.

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