By Brianna Shevlin

Adiabatic Temperature Changes and Expansion and CoolingTemperature changes, even without

adding or subtracting heat is called adiabatic temperature changes.

When air expands, it cools and when compressed, it warms.

Moving upward the air expands and cools due to passing regions of low pressure.

Cooling generates clouds and precipitation

Unsaturated air cools at 10 degrees Celsius every 1000 meters upward.

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Orographic LiftingElevated land, like mountains, that blocks air

flow proves orographic lifting is occuring.More rain occurs on the windward side.An example is the Great Basin Desert is cut

off by the Sierra Nevada Mountains.

examiner.com

Frontal WedgingWarm air colliding with cool air produces a

front.Cool dense air is a barrier to the warm air

that rises.

geo.hunter.cuny.edu

ConvergenceWhen air in the lower atmosphere flows

together, lifting occurs. This is called convergence.

Air flows from more then one direction and when it can’t go down, it goes up.

Convergence causes clouds and precipitation.

ww2010.atmos.uiuc.edu

Localized Collective LiftingUnequal heating of Earth’s

surface may cause pockets of air to be warmer then the surrounding air.

Rising parcels of warm air are called thermals.

Process that makes parcels is localized collective lifting.

Parcels that rise above condensation level results in the formation of clouds and possible rain showers.

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StabilityStability is when the air is cooler then its

surroundings.Air is dense and sinks to original position

resisting vertical movement.Difference:Stable air remains in the same position while

unstable air rises.Stability and Daily Weather:Stable air is forced upward by other

processesClouds are widespread and have little

vertical thickness.Lifting of unstable air results in thunder

storms and possible tornados.On overcast, dreary days stable air has been

forced upPuffy clouds means unstable air rose.

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Condensation Happens when water vapor in

the air changes to a liquid.Forms dew, fog, or clouds.Must be at a surface for the

water vapor to condense on.Clouds occur when water

vapor uses condensation nuclei as its surface.

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Types of CloudsClouds are classified

based on form and height.Cirrus: High, white, and

thin.Cumulus: Rounded and

individuals.Stratus: Sheets cover most

or all of the sky. There are no individual clouds.

Three levels of clouds: high, middle, and low.

eo.ucar.edu

High CloudsBases are above 6000 meters.Cirrocumulus:

fluffy.Cirrostratus :

flat layer, thin, white, and made up of ice crystals.

Due to low temperature (the higher, the cooler) and the small amount of water vapor there is no rain.

High clouds show warning of stormy weather

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Middle CloudsBases are 2000-6000 meters high.Altocumulous:

rounded, large, and dense.Altostratus:

White or gray sheet that covers the sky. Produce light snow drizzle.

bigbranch.net

Low CloudsBases are 2000 meters or below.Stratus:

Foggy layer that covers the skyProduce occasional precipitation

Stratocumulous: appear in patchesDevelop at the bottom of a stratus cloud.

Nimbostratus: They are the most common precipitation makersThey form during stable conditionsIt’s a rainy cloud that covers the sky.

eo.ucar.edu

Clouds of Vertical DevelopmentSome clouds don’t fit into

the three categories. Their base is at a low range

but extend upward into the middle and higher range.

Due to unstable air.One cloud is called

cumulonimbus which causes rain and thunderstorms.

Cumulus clouds fit in this category.

bigbranch.net

FogFog:Clouds with bases near the ground.Happens due to radiation cooling or movement or air over a

cool surface.Cooling:Cools rapidly by radiation on cool, clear nights.A thin layer of air near the ground is cooled below dewpoint.Air cools and becomes dense, draining into low areas.Evaporation:There is a steaming appearance.When cool air is over warm water there may be enough

moisture to evaporate and produce saturationIncrease in water vapor.

brainharmonycenter.com

Cold Cloud PrecipitationBergeron process relies on two

processes: supercooling and supersaturation.

Water below 0 degrees Celcuis is supercooled.

Ice crystals grow as cloud droplets do, when they are big enough they will fall.

When the surface temperature is above 4 degrees Celcuis, snowflakes will melt before reaching the ground.

rst.gsfc.nasa.gov

Warm Cloud PrecipitationIn warm clouds, the formation of raindrops is

called collision-coalescence process.Water absorbing particles remove water

vapor from air at relative humidity's less than 100% forming large drops that collide and join with smaller, slower droplets

apollo.lsc.vsc.edu

Rain and SnowRain means drops of water that

fall from a cloud.Small drops are called a drizzle.Snow turns to rain before even

hitting the ground when the surface temperature is above 4 degrees celcuis.

At low temperatures, light, fluffy snow made of ice crystals form.

At temperatures warmer than 5 degrees celcuis,I ice crystals are larger clumps.

roymiller.hubpages.com

itunes.apple.com

Sleet, Glaze, and HailSleet:The fall of small particles of clear ice.Forms when a layer of air with temperatures

above freezing over lay a subfreezing layer near the ground.

Glaze:Freezing rainHappens when raindrops become supercooled.Turn solid when impacting objects.Hail:Produces in cumulonimbus clouds.Small ice pelets grow by collection of supercooeld water droplets as they fall

through clouds.

wunderground.com

sercc.com

rufinope.comlu.com

Bri’s Presentation on Clouds and Precipitation!

The End!