cloud, precipitation, and wind

8/8/2019 Cloud, Precipitation, And Wind

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Cloud Typescommon cloud classifications

Clouds are classified into a system that uses Latin words to describe the appearance of clouds as

seen by an observer on the ground. The table below summarizes the four principal components

of this classification system (Ahrens, 1994).

Latin Root Translation Example

cumulus

stratuscirrus

nimbus

heap

layercurl of hair

rain

fair weather cumulus

altostratuscirrus

cumulonimbus

Further classification identifies clouds by height of cloud base. For example, cloud namescontaining the prefix "cirr-", as in cirrus clouds, are located at high levels while cloud names

with the prefix "alto-", as in altostratus, are found at middle levels. This module introducesseveral cloud groups. The first three groups are identified based upon their height above the

ground. The fourth group consists of vertically developed clouds, while the final group consistsof a collection of miscellaneous cloud types.

Photograph by: Knupp

High-Level Clouds

High-level clouds form above 20,000 feet (6,000 meters)and since the temperatures are so cold at such high

elevations, these clouds are primarily composed of ice

crystals. High-level clouds are typically thin and white inappearance, but can appear in a magnificent array of colors

when the sun is low on the horizon.
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Photograph by:Holle

Mid-Level CloudsThe bases of mid-level clouds typically appear between

6,500 to 20,000 feet (2,000 to 6,000 meters). Because of

their lower altitudes, they are composed primarily of

water droplets, however, they can also be composed ofice crystals when temperatures are cold enough.

Low-level CloudsLow clouds are of mostly composed of water droplets since their bases generally lie below 6,500

feet (2,000 meters). However, when temperatures are cold enough, these clouds may also contain

ice particles and snow.

Photograph by:Holle

Vertically Developed Clouds

Probably the most familiar of the classified clouds is the cumulus cloud. Generated mostcommonly through eitherthermal convectionorfrontal lifting, these clouds can grow to heights

in excess of 39,000 feet (12,000 meters), releasing incredible amounts of energy through the

condensationof water vapor within the cloud itself.
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Photograph by:Holle

Other Cloud TypesFinally, we will introduce a collection of miscellaneous cloud types which do not fit into the

previous four groups.

ClassificationsLast Update: 07/09/97

High-Level Clouds

Cloud types include: cirrus andcirrostratus.

Mid-Level CloudsCloud types include: altocumulus, altostratus.

Low-Level Clouds

Cloud types include: nimbostratus and stratocumulus.

Clouds with Vertical Development

Cloud types include: fair weather cumulus and cumulonimbus.

Other Cloud Types

Cloud types include: contrails,billow clouds, mammatus,orographic and

pileus clouds.

Cloud Classification

The classification of clouds was first conceptualized by French naturalist Jean Lamarck in 1801.

Two years later, in 1803, the English scientist Luke Howard created a classification which was

later adopted by the International Meteorological Commission in 1929.

The first scientific study of clouds began in 1803, when a method of cloud classification was

devised by the British meteorologist Luke Howard. The next development was the publication in

1887 of a classification system that later formed the basis for the noted International Cloud Atlas(1896). This atlas, considerably revised and modified through the years (most recently in 1956),

is now used throughout the world.
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Cloud types

Clouds are generally classified according to genera in which Latin words are used to describe the

appearance of clouds as seen by an observer on the ground. The table below summarizes the four

principal components of this classification system.Latin Root cumulus stratus cirrus nimbus

Translation heap layer curl of hair rain

Cloud altitude

Clouds are further categorized according to their height above the ground (etages). These are:

High-Level Clouds

Forms above 20,000 feet (6,000 meters) and are primarily composed of ice crystals.

Denoted by the prefix cirro- orcirrus and includes cirrus, cirrocumulus, and cirrostratus.

Mid-Level Clouds

Their bases appear between 6,500 to 20,000 feet (2,000 to 6,000 meters). Composed

primarily of water droplets although they can also be composed of ice crystals when

temperatures are cold enough. Denoted by the prefix alto- and includes altostratus,altocumulus and nimbostratus.

Low-level Clouds

Their bases generally lie below 6,500 feet (2,000 meters). Mostly composed of water

droplets but may also contain ice particles and snow. Includes stratus, stratocumulus,cumulus and cumulonimbus.

When cloud particles become too heavy to remain suspended in the air, they fall to the earth as

precipitation. Precipitation occurs in a variety of forms; hail, rain, freezing rain, sleet or snow.

This portion of the Clouds and Precipitation module focuses on precipitation and has beenorganized into the following sections.

SectionsLatest Update: 07/21/97

Rain and Hail

Atmospheric conditions that lead to the development of rain and hail.

Freezing Rain

A detailed look at freezing rain, associated dangers and the conditions thatlead to its development.

Sleet

Atmospheric conditions that lead to the development of sleet.

Snow
http://kidlat.pagasa.dost.gov.ph/genmet/clouds/c_highclouds.htmlhttp://kidlat.pagasa.dost.gov.ph/genmet/clouds/c_middleclouds.htmlhttp://kidlat.pagasa.dost.gov.ph/genmet/clouds/c_lowclouds.htmlhttp://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/cld/prcp/rnhl.rxmlhttp://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/cld/prcp/zr/frz.rxmlhttp://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/cld/prcp/slt.rxmlhttp://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/cld/prcp/snow.rxmlhttp://kidlat.pagasa.dost.gov.ph/genmet/clouds/c_highclouds.htmlhttp://kidlat.pagasa.dost.gov.ph/genmet/clouds/c_middleclouds.htmlhttp://kidlat.pagasa.dost.gov.ph/genmet/clouds/c_lowclouds.htmlhttp://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/cld/prcp/rnhl.rxmlhttp://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/cld/prcp/zr/frz.rxmlhttp://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/cld/prcp/slt.rxmlhttp://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/cld/prcp/snow.rxml


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warmer temperature regimes due to the process of its formation. Precipitation may occur on

other celestial bodies, e.g. when it gets cold, Mars has precipitation which most likely takes the

form of ice needles, rather than rain or snow.[3]

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, includingwetter conditions across easternNorth Americaand drier conditions in the tropics. Precipitation

is a major component of the water cycle, and is responsible for depositing most of the fresh wateron theplanet. Approximately 505,000 cubic kilometres (121,000 cu mi) of water falls as

precipitation each year; 398,000 cubic kilometres (95,000 cu mi) of it over the oceans.[4] Given

the Earth's surface area, that means the globally-averaged annual precipitation is 990 millimetres(39 in). Climate classification systems such as the Kppen climate classification system use

average annual rainfall to help differentiate between differing climate regimes.

Part of the Natureseries on

Weather

Calendar Seasons

Spring Summer

Autumn Winter

Tropical Seasons

Dry seasonWet season

Storms

ThunderstormSupercell

Downburst Lightning

TornadoWaterspout

Tropical cyclone (Hurricane)

Extratropical cyclone

Winter storm BlizzardIce storm

Dust storm Firestorm Cloud

Precipitation

Drizzle Rain Snow GraupelFreezing rain Ice pelletsHail

Topics

Meteorology Climate

Weather forecasting

Heat wave Air pollution
http://en.wikipedia.org/wiki/Marshttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#cite_note-mars-2http://en.wikipedia.org/wiki/Urban_heat_islandhttp://en.wikipedia.org/wiki/Global_warminghttp://en.wikipedia.org/wiki/North_Americahttp://en.wikipedia.org/wiki/North_Americahttp://en.wikipedia.org/wiki/Water_cyclehttp://en.wikipedia.org/wiki/Water_cyclehttp://en.wikipedia.org/wiki/Fresh_waterhttp://en.wikipedia.org/wiki/Planethttp://en.wikipedia.org/wiki/Oceanhttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#cite_note-chow-3http://en.wikipedia.org/wiki/Precipitation_(meteorology)#cite_note-chow-3http://en.wikipedia.org/wiki/Earthhttp://en.wikipedia.org/wiki/Earthhttp://en.wikipedia.org/wiki/Climatehttp://en.wikipedia.org/wiki/K%C3%B6ppen_climate_classificationhttp://en.wikipedia.org/wiki/Naturehttp://en.wikipedia.org/wiki/Naturehttp://en.wikipedia.org/wiki/Weatherhttp://en.wikipedia.org/wiki/Seasonhttp://en.wikipedia.org/wiki/Spring_(season)http://en.wikipedia.org/wiki/Summerhttp://en.wikipedia.org/wiki/Autumnhttp://en.wikipedia.org/wiki/Winterhttp://en.wikipedia.org/wiki/Tropicalhttp://en.wikipedia.org/wiki/Dry_seasonhttp://en.wikipedia.org/wiki/Dry_seasonhttp://en.wikipedia.org/wiki/Wet_seasonhttp://en.wikipedia.org/wiki/Wet_seasonhttp://en.wikipedia.org/wiki/Stormhttp://en.wikipedia.org/wiki/Thunderstormhttp://en.wikipedia.org/wiki/Thunderstormhttp://en.wikipedia.org/wiki/Supercellhttp://en.wikipedia.org/wiki/Supercellhttp://en.wikipedia.org/wiki/Downbursthttp://en.wikipedia.org/wiki/Lightninghttp://en.wikipedia.org/wiki/Tornadohttp://en.wikipedia.org/wiki/Tornadohttp://en.wikipedia.org/wiki/Waterspouthttp://en.wikipedia.org/wiki/Waterspouthttp://en.wikipedia.org/wiki/Tropical_cyclonehttp://en.wikipedia.org/wiki/Extratropical_cyclonehttp://en.wikipedia.org/wiki/Winter_stormhttp://en.wikipedia.org/wiki/Blizzardhttp://en.wikipedia.org/wiki/Blizzardhttp://en.wikipedia.org/wiki/Ice_stormhttp://en.wikipedia.org/wiki/Ice_stormhttp://en.wikipedia.org/wiki/Dust_stormhttp://en.wikipedia.org/wiki/Firestormhttp://en.wikipedia.org/wiki/Cloudhttp://en.wikipedia.org/wiki/Drizzlehttp://en.wikipedia.org/wiki/Rainhttp://en.wikipedia.org/wiki/Snowhttp://en.wikipedia.org/wiki/Graupelhttp://en.wikipedia.org/wiki/Freezing_rainhttp://en.wikipedia.org/wiki/Ice_pelletshttp://en.wikipedia.org/wiki/Ice_pelletshttp://en.wikipedia.org/wiki/Ice_pelletshttp://en.wikipedia.org/wiki/Hailhttp://en.wikipedia.org/wiki/Hailhttp://en.wikipedia.org/wiki/List_of_meteorology_topicshttp://en.wikipedia.org/wiki/Meteorologyhttp://en.wikipedia.org/wiki/Climatehttp://en.wikipedia.org/wiki/Weather_forecastinghttp://en.wikipedia.org/wiki/Heat_wavehttp://en.wikipedia.org/wiki/Air_pollutionhttp://en.wikipedia.org/wiki/Marshttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#cite_note-mars-2http://en.wikipedia.org/wiki/Urban_heat_islandhttp://en.wikipedia.org/wiki/Global_warminghttp://en.wikipedia.org/wiki/North_Americahttp://en.wikipedia.org/wiki/Water_cyclehttp://en.wikipedia.org/wiki/Fresh_waterhttp://en.wikipedia.org/wiki/Planethttp://en.wikipedia.org/wiki/Oceanhttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#cite_note-chow-3http://en.wikipedia.org/wiki/Earthhttp://en.wikipedia.org/wiki/Climatehttp://en.wikipedia.org/wiki/K%C3%B6ppen_climate_classificationhttp://en.wikipedia.org/wiki/Naturehttp://en.wikipedia.org/wiki/Weatherhttp://en.wikipedia.org/wiki/Seasonhttp://en.wikipedia.org/wiki/Spring_(season)http://en.wikipedia.org/wiki/Summerhttp://en.wikipedia.org/wiki/Autumnhttp://en.wikipedia.org/wiki/Winterhttp://en.wikipedia.org/wiki/Tropicalhttp://en.wikipedia.org/wiki/Dry_seasonhttp://en.wikipedia.org/wiki/Wet_seasonhttp://en.wikipedia.org/wiki/Stormhttp://en.wikipedia.org/wiki/Thunderstormhttp://en.wikipedia.org/wiki/Supercellhttp://en.wikipedia.org/wiki/Downbursthttp://en.wikipedia.org/wiki/Lightninghttp://en.wikipedia.org/wiki/Tornadohttp://en.wikipedia.org/wiki/Waterspouthttp://en.wikipedia.org/wiki/Tropical_cyclonehttp://en.wikipedia.org/wiki/Extratropical_cyclonehttp://en.wikipedia.org/wiki/Winter_stormhttp://en.wikipedia.org/wiki/Blizzardhttp://en.wikipedia.org/wiki/Ice_stormhttp://en.wikipedia.org/wiki/Dust_stormhttp://en.wikipedia.org/wiki/Firestormhttp://en.wikipedia.org/wiki/Cloudhttp://en.wikipedia.org/wiki/Drizzlehttp://en.wikipedia.org/wiki/Rainhttp://en.wikipedia.org/wiki/Snowhttp://en.wikipedia.org/wiki/Graupelhttp://en.wikipedia.org/wiki/Freezing_rainhttp://en.wikipedia.org/wiki/Ice_pelletshttp://en.wikipedia.org/wiki/Hailhttp://en.wikipedia.org/wiki/List_of_meteorology_topicshttp://en.wikipedia.org/wiki/Meteorologyhttp://en.wikipedia.org/wiki/Climatehttp://en.wikipedia.org/wiki/Weather_forecastinghttp://en.wikipedia.org/wiki/Heat_wavehttp://en.wikipedia.org/wiki/Air_pollution


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Weather Portal

vde

Contents

[hide]

1 Hydrometeor 2 Types 3 How the air becomes saturated

o 3.1 Cooling air to its dew pointo 3.2 Adding moisture to the air

4 Formationo 4.1 Raindropso 4.2 Ice pelletso 4.3 Hail

o 4.4 Snowflakeso 4.5 Diamond dust

5 Causeso 5.1 Frontal activityo 5.2 Convectiono 5.3 Orographic effectso 5.4 Snowo 5.5 Within the tropics

6 Measurement 7 Return period 8 Role in Kppen climate classification 9 Effect on agriculture

10 Changes due to global warming 11 Changes due to urban heat island 12 Forecasting 13 See also 14 References

15 External links

[edit] Hydrometeor
http://en.wikipedia.org/wiki/Portal:Weatherhttp://en.wikipedia.org/wiki/Template:Weatherhttp://en.wikipedia.org/wiki/Template:Weatherhttp://en.wikipedia.org/wiki/Template_talk:Weatherhttp://en.wikipedia.org/wiki/Template_talk:Weatherhttp://en.wikipedia.org/wiki/Template_talk:Weatherhttp://en.wikipedia.org/w/index.php?title=Template:Weather&action=edithttp://en.wikipedia.org/wiki/Precipitation_(meteorology)http://en.wikipedia.org/wiki/Precipitation_(meteorology)#Hydrometeorhttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#Typeshttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#How_the_air_becomes_saturatedhttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#Cooling_air_to_its_dew_pointhttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#Adding_moisture_to_the_airhttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#Formationhttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#Raindropshttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#Ice_pelletshttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#Hailhttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#Hailhttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#Snowflakeshttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#Diamond_dusthttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#Causeshttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#Frontal_activityhttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#Convectionhttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#Orographic_effectshttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#Snowhttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#Within_the_tropicshttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#Measurementhttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#Return_periodhttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#Role_in_K.C3.B6ppen_climate_classificationhttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#Effect_on_agriculturehttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#Changes_due_to_global_warminghttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#Changes_due_to_urban_heat_islandhttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#Forecastinghttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#See_alsohttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#Referenceshttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#External_linkshttp://en.wikipedia.org/w/index.php?title=Precipitation_(meteorology)&action=edit&section=1http://en.wikipedia.org/wiki/File:Anvil_cumulus_feb_2007.jpghttp://en.wikipedia.org/wiki/File:Anvil_cumulus_feb_2007.jpghttp://en.wikipedia.org/wiki/Portal:Weatherhttp://en.wikipedia.org/wiki/Template:Weatherhttp://en.wikipedia.org/wiki/Template_talk:Weatherhttp://en.wikipedia.org/w/index.php?title=Template:Weather&action=edithttp://en.wikipedia.org/wiki/Precipitation_(meteorology)http://en.wikipedia.org/wiki/Precipitation_(meteorology)#Hydrometeorhttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#Typeshttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#How_the_air_becomes_saturatedhttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#Cooling_air_to_its_dew_pointhttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#Adding_moisture_to_the_airhttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#Formationhttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#Raindropshttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#Ice_pelletshttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#Hailhttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#Snowflakeshttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#Diamond_dusthttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#Causeshttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#Frontal_activityhttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#Convectionhttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#Orographic_effectshttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#Snowhttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#Within_the_tropicshttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#Measurementhttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#Return_periodhttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#Role_in_K.C3.B6ppen_climate_classificationhttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#Effect_on_agriculturehttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#Changes_due_to_global_warminghttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#Changes_due_to_urban_heat_islandhttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#Forecastinghttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#See_alsohttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#Referenceshttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#External_linkshttp://en.wikipedia.org/w/index.php?title=Precipitation_(meteorology)&action=edit&section=1


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This anvil-shaped Cumulonimbus incus cloud is composed of hydrometeors.

The term meteordescribes an object fromouter space which has entered the Earth's atmosphereand produces a light phenomenon.[5] In contrast, any phenomenon which was at some point

produced due to condensation or precipitation of moisture within the Earth's atmosphere is

known as a hydrometeor. Particles composed of fallen precipitation which fell onto the Earth'ssurface can become hydrometeors if blown off the landscape by wind. Formations due tocondensation such as clouds,haze,fog, and mist are composed of hydrometeors. All

precipitation types are hydrometeors by definition, including virga, which is precipitation which

evaporates before reaching the ground. Particles removed from the Earth's surface by wind suchas blowing snow and blowing sea spray are also hydrometeors.[6]

[edit] TypesSee also: Precipitation types (meteorology)

A thunderstorm with heavy precipitation

Precipitation is a major component of thewater cycle, and is responsible for depositing most of

the fresh wateron theplanet. Approximately 505,000 km3 (121,000 cu mi) of water falls asprecipitation each year, 398,000 km3 (95,000 cu mi) of it over the oceans.[4] Given theEarth'ssurface area, that means the globally-averaged annual precipitation is 990 millimetres (39 in).

Mechanisms of producing precipitation include convective, stratiform,[7] and orographic rainfall.[8] Convective processes involve strong vertical motions that can cause the overturning of the

atmosphere in that location within an hour and cause heavy precipitation,[9] while stratiformprocesses involve weaker upward motions and less intense precipitation. Precipitation can be

divided into three categories, based on whether it falls as liquid water, liquid water that freezes

on contact with the surface, or ice. Mixtures of different types of precipitation, including types indifferent categories, can fall simultaneously. Liquid forms of precipitation include rain and

drizzle. Rain or drizzle that freezes on contact within a subfreezingair mass is called "freezingrain" or "freezing drizzle". Frozen forms of precipitation includesnow, ice needles, ice pellets,hail, andgraupel.[10]
http://en.wikipedia.org/wiki/Meteoroid#Meteorhttp://en.wikipedia.org/wiki/Outer_spacehttp://en.wikipedia.org/wiki/Outer_spacehttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#cite_note-4http://en.wikipedia.org/wiki/Hazehttp://en.wikipedia.org/wiki/Hazehttp://en.wikipedia.org/wiki/Foghttp://en.wikipedia.org/wiki/Foghttp://en.wikipedia.org/wiki/Misthttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#cite_note-5http://en.wikipedia.org/wiki/Precipitation_(meteorology)#cite_note-5http://en.wikipedia.org/w/index.php?title=Precipitation_(meteorology)&action=edit&section=2http://en.wikipedia.org/wiki/Precipitation_types_(meteorology)http://en.wikipedia.org/wiki/Water_cyclehttp://en.wikipedia.org/wiki/Water_cyclehttp://en.wikipedia.org/wiki/Fresh_waterhttp://en.wikipedia.org/wiki/Fresh_waterhttp://en.wikipedia.org/wiki/Planethttp://en.wikipedia.org/wiki/Planethttp://en.wikipedia.org/wiki/Oceanhttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#cite_note-chow-3http://en.wikipedia.org/wiki/Precipitation_(meteorology)#cite_note-chow-3http://en.wikipedia.org/wiki/Earthhttp://en.wikipedia.org/wiki/Earthhttp://en.wikipedia.org/wiki/Earthhttp://en.wikipedia.org/wiki/Stratus_cloudhttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#cite_note-6http://en.wikipedia.org/wiki/Precipitation_(meteorology)#cite_note-6http://en.wikipedia.org/wiki/Orographic_lifthttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#cite_note-7http://en.wikipedia.org/wiki/Precipitation_(meteorology)#cite_note-convection-8http://en.wikipedia.org/wiki/Precipitation_(meteorology)#cite_note-convection-8http://en.wikipedia.org/wiki/Air_masshttp://en.wikipedia.org/wiki/Air_masshttp://en.wikipedia.org/wiki/Snowhttp://en.wikipedia.org/wiki/Snowhttp://en.wikipedia.org/wiki/Diamond_dusthttp://en.wikipedia.org/wiki/Ice_pellethttp://en.wikipedia.org/wiki/Ice_pellethttp://en.wikipedia.org/wiki/Hailhttp://en.wikipedia.org/wiki/Graupelhttp://en.wikipedia.org/wiki/Graupelhttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#cite_note-9http://en.wikipedia.org/wiki/Precipitation_(meteorology)#cite_note-9http://en.wikipedia.org/wiki/File:FoggDam-NT.jpghttp://en.wikipedia.org/wiki/File:FoggDam-NT.jpghttp://en.wikipedia.org/wiki/Meteoroid#Meteorhttp://en.wikipedia.org/wiki/Outer_spacehttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#cite_note-4http://en.wikipedia.org/wiki/Hazehttp://en.wikipedia.org/wiki/Foghttp://en.wikipedia.org/wiki/Misthttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#cite_note-5http://en.wikipedia.org/w/index.php?title=Precipitation_(meteorology)&action=edit&section=2http://en.wikipedia.org/wiki/Precipitation_types_(meteorology)http://en.wikipedia.org/wiki/Water_cyclehttp://en.wikipedia.org/wiki/Fresh_waterhttp://en.wikipedia.org/wiki/Planethttp://en.wikipedia.org/wiki/Oceanhttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#cite_note-chow-3http://en.wikipedia.org/wiki/Earthhttp://en.wikipedia.org/wiki/Stratus_cloudhttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#cite_note-6http://en.wikipedia.org/wiki/Orographic_lifthttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#cite_note-7http://en.wikipedia.org/wiki/Precipitation_(meteorology)#cite_note-convection-8http://en.wikipedia.org/wiki/Air_masshttp://en.wikipedia.org/wiki/Snowhttp://en.wikipedia.org/wiki/Diamond_dusthttp://en.wikipedia.org/wiki/Ice_pellethttp://en.wikipedia.org/wiki/Hailhttp://en.wikipedia.org/wiki/Graupelhttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#cite_note-9


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[edit] How the air becomes saturated

[edit] Cooling air to its dew point

Late-summer rainstorm in Denmark

Air contains water vapour, measured in grams of water per kilogram of dry air (g/kg), [11] 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. Therefore,

one way to saturate a parcel of air is to cool it. Thedew pointis the temperature to which a

parcel must be cooled in order to become saturated.[12]Water vapour normally begins to

condense on condensation nucleisuch as dust, ice, and salt in order to form clouds. An elevatedportion 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. It can also form due to the lifting ofadvection fog duringbreezy conditions.[13]

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.[14] The air can rise due to convection, large-scale atmospheric motions, or aphysical barrier such as a mountain (orographic lift). Conductive cooling occurs when the air

comes into contact with a colder surface,[15] usually by being blown from one surface to another,

for example from a liquid water surface to colder land. Radiational cooling occurs due to theemission ofinfrared radiation, either by the air or by the surface underneath.[16]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.[17]
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Lenticular cloud forming due to mountains over Wyoming

[edit] Adding moisture to the air

The main ways water vapour is added to the air are: wind convergence into areas of upward

motion,[9]

precipitation or virga falling from above,[18]

daytime heating evaporating water fromthe surface of oceans, water bodies or wet land,[19] transpiration from plants,[20] cool or dry air

moving over warmer water,[21] and lifting air over mountains.[22]

[edit] FormationMain article: Water cycle

Condensation and coalescence are important parts of the water cycle.

[edit] Raindrops

Coalescence occurs when water droplets fuse to create larger water droplets, or when waterdroplets 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. In clouds below

freezing, when ice crystals gain enough mass they begin to fall. This generally requires more
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mass than coalescence when occurring between the crystal and neighboring water droplets. 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 andground level, these ice crystals may melt as they fall and become rain.[23]

Raindrops have sizes ranging from 0.1 millimetres (0.0039 in) to 9 millimetres (0.35 in) meandiameter, 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 largestcross-section facing the oncoming airflow. Contrary to the cartoon pictures of raindrops, their

shape does not resemble a teardrop.[24] 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 canhave a long duration.[25][26] Rain drops associated with melting hail tend to be larger than other

rain drops.[27] The METAR code for rain is RA, while the coding for rain showers is SHRA.[28]

[edit] Ice pellets

See also: Ice pellets

An accumulation of ice pellets

Ice pellets are a form of precipitation consisting of small,translucentballs of ice. This form of

precipitation is also known as sleetin the United States.[29]Ice pellets are usually (but notalways) smaller than hailstones.[30] They often bounce when they hit the ground, and generally do

not freeze into a solid mass unless mixed with freezing rain. The METARcode for ice pellets is

PL.[28]

Ice pellets form when a layer of above-freezing air is located between 1,500 metres (4,900 ft)and 3,000 metres (9,800 ft) above the ground, with sub-freezing air both above and below it.

This causes the partial or complete melting of any snowflakes falling through the warm layer. Asthey fall back into the sub-freezing layer closer to the surface, they re-freeze into ice pellets.However, if the sub-freezing layer beneath the warm layer is too small, the precipitation will not

have time to re-freeze, and freezing rainwill be the result at the surface. A temperature profile

showing a warm layer above the ground is most likely to be found in advance of a warm frontduring the cold season [31], but can occasionally be found behind a passingcold front.

[edit] Hail
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See also: Hail

A large hailstone, about 6 cm (2.36 in) in diameter

Like other precipitation, hail forms in storm cloudswhen supercooledwaterdroplets freeze oncontact with condensation nuclei, such as dust ordirt. The storm's updraft blows the hailstones to

the upper part of the cloud. The updraft dissipates and the hailstones fall down, back into the

updraft, and are lifted up again. Hail has a diameter of 5 millimetres (0.20 in) or more.[32]

WithinMETAR code, GR is used to indicate larger hail, of a diameter of at least 6.4 millimetres (0.25in). GR is derived from the French word grle. Smaller-sized hail, as well as snow pellets, use

the coding of GS, which is short for the French word grsil. [28] Stones just larger than golf ball-

sized are one of the most frequently reported hail sizes.[33] Hailstones can grow to 15 centimetres(6 in) and weigh more than .5 kilograms (1.1 lb).[34]In large hailstones, latent heat released by

further freezing may melt the outer shell of the hailstone. The hailstone then may undergo 'wet

growth', where the liquid outer shell collects other smaller hailstones.[35] The hailstone gains anice layer and grows increasingly larger with each ascent. Once a hailstone becomes too heavy to

be supported by the storm's updraft, it falls from the cloud. [36]

Hail forms in strong thunderstorm clouds, particularly those with intense updrafts, high liquidwater content, great vertical extent, large water droplets, and where a good portion of the cloudlayer is below freezing 0 C (32 F).[32] Hail-producing clouds are often identifiable by their

green coloration.[37][38] The growth rate is maximized at about 13 C (9 F), and becomes

vanishingly small much below 30 C (22 F) as supercooled water droplets become rare. For

this reason, hail is most common within continental interiors of the mid-latitudes, as hailformation is considerably more likely when the freezing level is below the altitude of 11,000 feet

(3,400 m).[39]Entrainmentof dry air into strong thunderstorms over continents can increase the

frequency of hail by promoting evaporational cooling which lowers the freezing level ofthunderstorm clouds giving hail a larger volume to grow in. Accordingly, hail is actually less

common in the tropics despite a much higher frequency of thunderstorms than in the mid-

latitudes because the atmosphere over the tropics tends to be warmer over a much greater depth.Hail in the tropics occurs mainly at higher elevations.[40]

[edit] Snowflakes

Main article: Snowflake
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Snowflake viewed in an optical microscope

Snow crystals form when tiny supercooled cloud droplets (about 10 m in diameter) freeze.

These droplets are able to remain liquid at temperatures lower than 18 C (0 F), because tofreeze, a fewmoleculesin the droplet need to get together by chance to form an arrangement

similar to that in an ice lattice; then the droplet freezes around this "nucleus." Experiments show

that this "homogeneous" nucleation of cloud droplets only occurs at temperatures lower than

35 C (31 F).[41] In warmer clouds an aerosol particle or "ice nucleus" must be present in (orin contact with) the droplet to act as a nucleus. Our understanding of what particles make

efficient ice nuclei is poor what we do know is they are very rare compared to that cloud

condensation nuclei on which liquid droplets form. Clays, desert dust and biological particlesmay be effective,[42] although to what extent is unclear. Artificial nuclei include particles ofsilver

iodide anddry ice, and these are used to stimulate precipitation in cloud seeding.[43]

Once a droplet has frozen, it grows in the supersaturated environment, which is one where air issaturated with respect to ice when the temperature is below the freezing point. The droplet thengrows by diffusion of water molecules in the air (vapor) onto the ice crystal surface where they

are collected. Because water droplets are so much more numerous than the ice crystals due to

their sheer abundance, the crystals are able to grow to hundreds ofmicrometers or millimeters insize at the expense of the water droplets. This process is known as the Wegner-Bergeron-

Findeison process. The corresponding depletion of water vapor causes the droplets to evaporate,

meaning that the ice crystals grow at the droplets' expense. These large crystals are an efficientsource of precipitation, since they fall through the atmosphere due to their mass, and may collide

and stick together in clusters, or aggregates. These aggregates are snowflakes, and are usually the

type of ice particle that falls to the ground.[44] Guinness World Records list the worlds largest

snowflakes as those of January 1887 at Fort Keogh, Montana; allegedly one measured 38 cm(15 inches) wide.[45]

The exact details of the sticking mechanism remain controversial. Possibilities include

mechanical interlocking,sintering, electrostatic attraction as well as the existence of a "sticky"liquid-like layer on the crystal surface. The individual ice crystals often havehexagonal

symmetry. Although the ice is clear, scattering of light by the crystal facets and

hollows/imperfections mean that the crystals often appear white in color due todiffuse reflection
http://en.wikipedia.org/wiki/Supercoolhttp://en.wikipedia.org/wiki/%CE%9Cmhttp://en.wikipedia.org/wiki/Freezinghttp://en.wikipedia.org/wiki/Celsiushttp://en.wikipedia.org/wiki/Fahrenheithttp://en.wikipedia.org/wiki/Moleculeshttp://en.wikipedia.org/wiki/Moleculeshttp://en.wikipedia.org/wiki/Moleculeshttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#cite_note-Mason-40http://en.wikipedia.org/wiki/Precipitation_(meteorology)#cite_note-Christner2008-41http://en.wikipedia.org/wiki/Silver_iodidehttp://en.wikipedia.org/wiki/Silver_iodidehttp://en.wikipedia.org/wiki/Dry_icehttp://en.wikipedia.org/wiki/Dry_icehttp://en.wikipedia.org/wiki/Cloud_seedinghttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#cite_note-42http://en.wikipedia.org/wiki/Precipitation_(meteorology)#cite_note-42http://en.wikipedia.org/wiki/Micrometerhttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#cite_note-natgeojan07-43http://en.wikipedia.org/wiki/Precipitation_(meteorology)#cite_note-44http://en.wikipedia.org/wiki/Sinteringhttp://en.wikipedia.org/wiki/Sinteringhttp://en.wikipedia.org/wiki/Hexagonal_symmetryhttp://en.wikipedia.org/wiki/Hexagonal_symmetryhttp://en.wikipedia.org/wiki/Hexagonal_symmetryhttp://en.wikipedia.org/wiki/Diffuse_reflectionhttp://en.wikipedia.org/wiki/Diffuse_reflectionhttp://en.wikipedia.org/wiki/File:Snowflake_-_Microphotograph_by_artgeek.jpghttp://en.wikipedia.org/wiki/File:Snowflake_-_Microphotograph_by_artgeek.jpghttp://en.wikipedia.org/wiki/Supercoolhttp://en.wikipedia.org/wiki/%CE%9Cmhttp://en.wikipedia.org/wiki/Freezinghttp://en.wikipedia.org/wiki/Celsiushttp://en.wikipedia.org/wiki/Fahrenheithttp://en.wikipedia.org/wiki/Moleculeshttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#cite_note-Mason-40http://en.wikipedia.org/wiki/Precipitation_(meteorology)#cite_note-Christner2008-41http://en.wikipedia.org/wiki/Silver_iodidehttp://en.wikipedia.org/wiki/Silver_iodidehttp://en.wikipedia.org/wiki/Dry_icehttp://en.wikipedia.org/wiki/Cloud_seedinghttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#cite_note-42http://en.wikipedia.org/wiki/Micrometerhttp://en.wikipedia.org/wiki/Precipitation_(meteorology)#cite_note-natgeojan07-43http://en.wikipedia.org/wiki/Precipitation_(meteorology)#cite_note-44http://en.wikipedia.org/wiki/Sinteringhttp://en.wikipedia.org/wiki/Hexagonal_symmetryhttp://en.wikipedia.org/wiki/Hexagonal_symmetryhttp://en.wikipedia.org/wiki/Diffuse_reflection


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of the whole spectrum oflight by the small ice particles.[46] The shape of the snowflake is

determined broadly by the temperature and humidity at which it is formed.[44]Rarely, at a

temperature of around 2 C (28 F), snowflakes can form in threefold symmetry triangularsnowflakes.[47] The most common snow particles are visibly irregular, although near-perfect

snowflakes may be more common in pictures because they are more visually appealing. No two

snowflakes are alike due to the 10,000,000,000,000,000,000 water molecules which make up asnowflake,[48] which grow at different rates and in different patterns depending on the changing

temperature and humidity within the atmosphere that the snowflake falls through on its way to

the ground.[49]The METAR code for snow is SN, while snow showers are coded SHSN.[28]

[edit] Diamond dust

See also: Diamond dust

Diamond dust, also known as ice needles or ice crystals, forms at temperatures approaching

40 F (40 C) due to air with slightly higher moisture from aloft mixing with colder, surface

based air.[50]

They are made of simple ice crystals that are hexagonal in shape.[51]

The METARidentifier for diamond dust within international hourly weather reports is IC.[28]

[edit] Causes

[edit] Frontal activity

Main article: Weather fronts

Stratiform or dynamic precipitation occurs as a consequence of slow ascent of air in synopticsystems (on the order of cm/s), such as over surfacecold fronts, and over and ahead ofwarm

fronts. Similar ascent is seen around tropical cyclones outside of the eyewall, and in comma-head

precipitation patterns around mid-latitude cyclones.[52]

A wide variety of weather can be foundalong an occluded front, with thunderstorms possible, but usually their passage is associated witha drying of the air mass. Occluded fronts usually form around mature low-pressure areas.[53]

Precipitation may occur on celestial bodies other than Earth. When it gets cold, Mars has

precipitation that most likely takes the form of ice needles, rather than rain or snow.[3]

[edit] Convection

Convective precipitation
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Convective rain, or showery precipitation, occurs from convective clouds, e.g., cumulonimbusor

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 horizontalextent. Most precipitation in thetropicsappears to be convective; however, it has been suggested

that stratiform precipitation also occurs.[52][54]Graupel and hail indicate convection.[55] In mid-

latitudes, convective precipitation is intermittent and often associated with baroclinic boundariessuch as cold fronts, squall lines, and warm fronts.[56]

[edit] Orographic effects

Main articles: Orographic lift, Precipitation types (meteorology), and United States

rainfall climatology

Orographic precipitation

Orographic precipitation occurs on the windwardside of mountains and is caused by the risingair 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 consistentwinds (for example, the trade winds), a more moist climate usually prevails on the windwardside of a mountain than on the leewardor downwind side. 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.[22]

In Hawaii, Mount Wai ale ale , on the island of Kauai, is notable for its extreme rainfall, as it hasthe second highest average annual rainfall on Earth, with 460 inches (12,000 mm).[57] Storm

systems affect the state with heavy rains between October and March. Local climates vary

considerably on each island due to their topography, divisible into windward (Koolau) and

leeward (Kona) regions based upon location relative to the higher mountains. Windward sides

face the east to northeasttrade windsand receive much more rainfall; leeward sides are drier andsunnier, with less rain and less cloud cover.[58]

In South America, the Andes mountain range blocks Pacificmoisture that arrives in that

continent, resulting in a desertlike climate just downwind across western Argentina.[59]The SierraNevada range creates the same effect in North America forming the Great BasinandMojave

Deserts.[60][61]
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[edit] Snow

See also: Snow

Preferred region of heavy snowfall ("Banded Snowfall") around the comma head of a

wintertime low pressure area, shaded in green

Lake-effect snow bands near the Korean Peninsula

Extratropical cyclones can bring cold and dangerous conditions with heavy rain and snow withwinds exceeding 119 km/h (74 mph),[62] (sometimes referred to aswindstorms in Europe). The

band of precipitation that is associated with theirwarm frontis often extensive, forced by weak

upward vertical motion of air over the frontal boundary which condenses as it cools andproduces precipitation within an elongated band,[63] which is wide andstratiform, meaning falling

out ofnimbostratus clouds.[64]When moist air tries to dislodge an arctic air mass, overrunning

snow can result within the poleward side of the elongatedprecipitation band. In theNorthern

Hemisphere, poleward is towards theNorth Pole, or north. Within the Southern Hemisphere,

poleward is towards the South Pole, or south.

Within the cold sector, poleward and west of the cyclone center, small scaleormesoscale bands

of heavy snow can occur within a cyclone's comma-head pattern. This pattern is a comma-

shaped area of clouds and precipitation found around mature extratropical cyclones. These snowbands typically have a width of 20 miles (32 km) to 50 miles (80 km).[65] The bands in the

comma head are associated with areas offrontogenesis, or zones of strengthening temperature

contrast.[66]
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Southwest of extratropical cyclones, curved cyclonic flow bringing cold air across the relatively

warm water bodies can lead to narrow lake-effect snow bands. Those bands bring strong

localized snowfall which can be understood as follows: Large water bodies such as lakesefficiently store heat that results in significant temperature differences (larger than 13 C or

23 F) between the water surface and the air above.[67]Because of this temperature difference,

warmth and moisture are transported upward, condensing into vertically oriented clouds (seesatellite picture) which produce snow showers. The temperature decrease with height and cloud

depth are directly affected by both the water temperature and the large-scale environment. The

stronger the temperature decrease with height, the deeper the clouds get, and the greater theprecipitation rate becomes.[68]

In mountainous areas, heavy snowfall accumulates when air is forced to ascend the mountains

and squeeze out precipitation along their windward slopes, which in cold conditions, falls in the

form of snow. Because of the ruggedness of terrain, forecasting the location of heavy snowfallremains a significant challenge.[69]

[edit] Within the tropics

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

location

See also: Monsoon andTropical cyclone

Main article: Wet season

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.[70] The termgreen season is also sometimes used as a

euphemismby tourist authorities.[71]

Areas with wet seasons are dispersed across portions of thetropics and subtropics.[72]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.[73] Some areas with pronounced rainy seasons willsee a break in rainfall mid-season when theintertropical convergence zone ormonsoon trough

move poleward of their location during the middle of the warm season.[25] When the wet season

occurs during the warm season, orsummer, rain falls mainly during the late afternoon and earlyevening hours. The wet season is a time when air qualityimproves,[74] freshwater quality
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improves,[75][76] and vegetation grows significantly.Soil nutrients diminish and erosion increases.[25] Animals have adaptation and survival strategies for the wetter regime. Unfortunately, the

previous dry season leads to food shortages into the wet season, as the crops have yet to mature.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.[77]

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 ineither a clockwise direction (southern hemisphere) or counterclockwise (northern hemisphere).[78]

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.[79] Areas in their path can receive a year's worth of

rainfall from a tropical cyclone passage.[80]

[edit] Measurement

Standard rain gauge

See also: Rain gauge, Disdrometer, and Snow 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.[81] The inner cylinder is filledby 25 mm (1 in) of rain, with overflow flowing into the outer cylinder. Plastic gauges 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
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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. These gauges are used in the winter by removing the funnel and inner cylinderand allowing snow and freezing rain to collect inside the outer cylinder. Some add anti-freeze to

their gauge so they do not have to melt the snow or ice that falls into the gauge.[82] Once the

snowfall/ice is finished accumulating, or as you approach 300 mm (12 in), one can either bring itinside to melt, or use luke warm water to fill the inner cylinder with in order to melt the frozen

precipitation in the outer cylinder, keeping track of the warm fluid added, which is subsequently

subtracted from the overall total once all the ice/snow is melted.[83]

Other types of gauges include the popular wedge gauge (the cheapest rain gauge and mostfragile), the tipping bucket rain gauge, and the weighing rain gauge.[84] The wedge and tipping

bucket gauges will have problems with snow. Attempts to compensate for snow/ice by warming

the tipping bucket meet with limited success, since snow may sublimate if the gauge is keptmuch above freezing. Weighing gauges with antifreeze should do fine with snow, but again, the

funnel needs to be removed before the event begins. 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 outin the open, but its accuracy will depend on what ruler you use to measure the rain with. Any ofthe above rain gauges can be made at home, with enough know-how.[85]

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 asCoCoRAHS or GLOBE.[86][87]If a network is not available in the area where one lives, the

nearest local weather office will likely be interested in the measurement.[88]

[edit] Return periodSee also: 100-year flood

The likelihood or probability of an event with a specified intensity and duration, is called thereturn periodor frequency.[89] The intensity of a storm can be predicted for any return period and

storm duration, from charts based on historic data for the location.[90] The term 1 in 10 yearstorm 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. The rainfall will be greater and the flooding will beworse than the worst storm expected in any single year. 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 andflooding to be worse than a 1 in 10 year event. As with all probability events, it is possible to

have multiple "1 in 100 Year Storms" in a single year. [91]
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cloud, precipitation, and wind

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