Clouds and PrecipitationBy: Jessica Keller

Period 4

Adiabatic Temperature Changes and Expansion and CoolingThese are the temperature changes that happen even though

heat is not added or subtracted, the result is when the air is compressed.

When the air is allowed to expand, it cools, and when the air is compressed, it warms.

The latent heat works against the adiabatic cooling process, even though the air will continue to cool.

Orographic LiftingWhen there are elevated terrains, like mountains, they act

like a barrier to the air flow.When the air goes up a slope on a mountain, the adiabatic

cooling makes clouds and precipitation.An example of this would be, the Great Basin, it lies a few

hundred kilometers from the Pacific Ocean, and it is cut off from the ocean’s moisture by the Sierra Nevada Mountains.

Frontal WedgingOccurs when the masses of warm air, and the

masses of cold air collide a form a front.The cooler and denser air acts like a barrier

over the warm, less dense air, which rises.These weather producing fronts coordinate

with storms called middle latitude cyclones.

ConvergenceWhen air masses collide , it makes the air rise

and whenever air is in the lower atmosphere, the result is lifting.

When air flows in from more than one direction, the air rises.

And example of this would be the Florida Peninsula, on warm days the flow of air is from the ocean to the land, causing a pileup of air along the coasts and causes convergence over the peninsula.

Localized Convective LiftingThe uneven heating of the Earth’s surface may cause

pockets of air to be heated more than the air around them.The process of convective lifting produces thermals, which

is the rising air.Also, when the warm air rises above the condensation level,

this is clouds form using convective lifting.

Stability (Density Differences & Stability & Daily Weather) When air rises, its temperature drops because it is expanding, but

if it was cooler than the air surrounding it then it would sink. This is called stable air, which resists vertical movement. Stability Movements- The stability of the air is determined by

measuring the temperature at different heights. Degrees of Stability- Air is considered stable when the

temperature decreases with increasing altitude. Stability and Daily Weather- Has to do with the creation of

clouds using orographic lifting, frontal wedging, and convergence.

CondensationCondensation is when the water vapor in the

air changes to a liquid.It can occur in a form of fog, dew or clouds.For these condensation to occur, however, the

air must be saturated, which is when the air is cooled to its dew point.

Types of Clouds There are three types of clouds, these include:

Cirrus Clouds- These are high, white, and thin clouds. They occur as patches or fibers and have a feather like appearance.

Cumulus Clouds- These clouds are clouds that consist of round, big cloud masses. They normally have a flat base and tend to be very big.

Stratus Clouds- These clouds look like sheets because they are in layers and cover most of the sky.

High CloudsThe high clouds are made up of three

different types of clouds: Cirrus, Cirrostratus, and Cirrocumulus.

The high clouds are often thin and white and made up of ice crystals, which form because of the very low temperatures.

These clouds are not usually precipitation makers.

Middle CloudsThe middle clouds appear in the sky in the

middle range, usually between 2000 to 6000 meters.

Made up of Altocumulus clouds, which are composed of rounded cloud masses. These clouds are also larger and denser then most.

These clouds may experience infrequent light snow, or drizzle.

Low Clouds The low clouds are made up of three different

types of clouds: Stratus, Stratocumulus, and Nimbostratus.

These clouds cover most of the sky, and may produce some precipitation.

However Nimbostratus clouds are one of the main precipitation makers, and form during stable conditions.

Clouds of Vertical DevelopmentSome of the clouds have their bases in the low height range

but they often extend up into the middle or even high altitudes, however they all relate to stable air.

Whenever there is a upward movement, the acceleration is powerful and what forms is clouds with great vertical range.

The end result is a Cumulonimbus cloud that produces rain and thunderstorms.

Fog (By Cooling and By Evaporation)Fog is defined as a cloud with its base at or near the

ground.Fog cause by cooling is formed on cool, clear nights when

the Earth’s surface is cooled by radiation. When the air comes in contact with the ground it is cooled below its dew point, which creates fog.

Fog cause by evaporation when cool air moves over warm water and the moisture is evaporated to produce saturation. When the rising water meets the cold air, it condenses and causes fog.

Cold Cloud Precipitation (Bergeron Process)Cold cloud precipitation relies on two

physical processes: super cooling and super saturation.

When water is in the liquid state below zero degrees Celsius it is super cooled.

When the air is saturated, it is considered super saturated.

Warm Cloud Precipitation (Collision-Coalescence Process)In a warm cloud, the Collision- Coalescence

Process is what forms raindrops.When water absorbing particles, like salt,

remove water vapor from the air, at relative humidities less than 100%, this forms large raindrops.

As these large raindrops move throughout the cloud they collide and join together with smaller droplets.

Rain and SnowThe definition of rain is drops of water that

fall from a cloud and have a diameter of 0.5 mm.

Also, when the surface temperature is 4 degrees Celsius, the snowflakes usually melt and fall as rain.

At very low temperatures, snow occurs, which is light, fluffy, and made up of six sided ice crystals.

Sleet, Glaze and HailSleet is small particles that are clear, and

form a layer of air with temperatures above freezing.

Glaze is like a freezing rain, and happens when raindrops get super cooled as they go through subfreezing air.

Hail is made in Cumulonimbus clouds, and begin as only small ice particles, but grow by collecting super cooled water droplets.

Works Cited (Pictures) http://www.kidsgeo.com/geography-for-kids/0070-adiabatic-temperature-ch

anges.php

Adiabatic Temperature Changes and Expansion and Cooling http://ocw.usu.edu/Forest__Range__and_Wildlife_Sciences/Wildland_Fire_M

anagement_and_Planning/Unit_7__Atmospheric_Stability_and_Instability_3.html

Orographic Lifting http://www.geo.hunter.cuny.edu/~tbw/wc.notes/4.moisture.atm.stability/fro

ntal_wedging.htm

Frontal Wedging http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/cld/dvlp/cnvrg.rxml

Convergence https://www.meted.ucar.edu/sign_in.php?go_back_to=http%253A%252F%2

52Fwww.meted.ucar.edu%252Fnorlat%252Fsnow%252Flake_effect%252Fprint_whole.htm

Localized Convective Lifting

Works Cited Cont. (Pictures) http://www.fas.org/irp/imint/docs/rst/Sect14/Sect14_1b.html

Stability http://keep3.sjfc.edu/students/kes00898/e-port/condensation%20page%20f

or%20unit.html

Condensation http://www.enchantedlearning.com/subjects/astronomy/planets/earth/cloud

s/

Types Of Clouds http://cimss.ssec.wisc.edu/satmet/modules/clouds/highclouds.html

High Clouds http://www.climate4you.com/ClimateAndClouds.htm

Middle Clouds http://www.atmos.illinois.edu/earths_atmosphere/clouds.html

Low Clouds

Works Cited Cont. (Pictures) http://

www.free-online-private-pilot-ground-school.com/Aviation-Weather-Principles.html

Clouds of Vertical Development http://www.google.com/imgres?

q=fog&hl=en&safe=active&biw=1365&bih=559&gbv=2&tbm=isch&tbnid=VvVXTe2iWya2PM:&imgrefurl=http://www.brainharmonycenter.com/brain-fog.html&docid=uZKGt4B2tjgIaM&imgurl=http://www.brainharmonycenter.com/images/brain-fog.jpg&w=800&h=600&ei=-6z0TsmVKqje0QHK5b2wAg&zoom=1&iact=rc&dur=218&sig=115237740818284051629&page=1&tbnh=119&tbnw=160&start=0&ndsp=23&ved=1t:429,r:4,s:0&tx=53&ty=62

Fog http://dnr.wi.gov/org/caer/ce/eek/earth/groundwater/precip.htm

Cold Cloud Precipitation http://

all-free-download.com/free-vector/vector-clip-art/rain_cloud_clip_art_17461.html

Warm Cloud Precipitation

Works Cited Cont. (Pictures) http://www.windows2universe.org/earth/Atmosphere/precipitation.html

Rain and Snow http://www.edupic.net/weather_gr.htm

Sleet, Glaze, and Hail