CLOUDS AND PRECIPITATION

By: Jorge Rodriguez

Adiabatic temperature changes and expansion and cooling

When temperature is changing even though heat isn't being given or taken away

When air expands it cools and when air is compressed it gets warm, when this happens this is called dry adiabatic rate

When cooling is at a slower rate because of heat is being added it is called wet adiabatic

Orographic lifting

Mountains act as barriers to air flow As air goes up the mountain slope

adiabatic cooling begins to make clouds and precipitation

When the air reaches the leeward side of he mountain most of its moisture has been lost and condensation and precipitation is less likely to happen

http://www.sci.uidaho.edu/scripter/geog100/lect/05-atmos-water-wx/05-part-7-atmos-lifting-fronts/ch5-part-7a-atmos-liftin.htm

Frontal wedging When masses of warm air and cold air

collide producing a front Cool denser air act as a barrier over the

less denser air. Weather producing fronts are associated

with specific storm systems which is called middle latitude cyclones

Convergence

When air flows in from more than one direction it begins to flow upward because it cant go down

Causes cloud development and precipitation

Air movement and the rise of it is helped by solar heating of the land

Stability(density difference and stability and daily weather

When the volume of air was forced to rise, its temperature will drop because of its expansion

The warm air that is less dense in its surrounding air, will keep going upward until it reaches a altitude where its temperature equals its surrounding air

When stable air is moved above the earth surface, the clouds that form are widespread and have little vertical thickness.

Condensation

When water vapor in the air changes to a liquid

When condensation happens in the air above the ground, tiny bits of particulate matter called condensation nuclei are used as a surface for water vapor condensation

When condensation happens the growth rate of cloud droplets is very rapid

Types of clouds

All clouds are one of these basic forms: cirrus, cumulus and stratus

Cirrus clouds are high white and thin, they have a feathery appearance also occur as delicate veil like sheets

Cumulus clouds normally have a flat base and look like rising domes or towers, they clouds are describe of having a cauliflower structure

Stratus clouds are layers that cover up most of the sky

High clouds

Normally have a bases of 6000 meters Three could types make up the family of

the high clouds, cirrus, cirrostratus and cirrocumulus

All high clouds are thin and white and are often made up of crystal ice

High clouds are not consider precipitation makers

Middle clouds

Middle clouds occupy heights from 2000 to 6000 meters, have the prefix alto in their name

Altocumulus clouds are larger and denser than cirrocumulus clouds

Altostratus clouds a white and grayish sheet covering the sky with the sun or moon

Light snow or drizzle may accompany these clouds

Low clouds Low clouds form below 2000 meters there are three members of the low cloud family

they are stratus, stratocumulus and nimbostratus

Stratus clouds are a fog like layers of clouds the cover up most of the sky

Stratocumulus clouds are when stratus clouds create a scalloped bottom that appear long parallel rolls

Nimbostratus clouds form during stable air, this cloud is one of the main precipitation makers

Clouds of vertical development

These clouds aren’t in any of the other three height categories, they are in the low height range

Often extend to middle or high altitude They are all related to unstable air except

the cumulus cloud, that is connected to fair weather

Fog(by cooling and by evaporation

Fogs are the result of radiation cooling or the movement of air over a cooled surface

Fogs can also form by cool air because of the earth surface cools rapidly by radiation

Fog also is caused by evaporation because when rising water vapor meets cold air it begins to condense and rise with the air that is being warmed from below

Cold cloud precipitation(bergeron process) The bergeron process relies on two

physical process which is super cooling and supersaturated

Super cooling is when water is in the liquid state but under 0 degrees Celsius

Supersaturated is when air is 100 percent relative humidity

Warm cloud precipitation(collision-coalescene process)

salt the water absorbing particle can remove water vapor from the air even if the relative humidity is less than 100 percent

Large water droplets form the humidity that is being taken away as these droplets move through the clouds they begin to collide

Rain and snow

The term rain means water that falls from clouds and that a diameter of .5 mm

When temperature is above 4 degrees Celsius snow flakes will melt and turn into rain before they hit the ground

When temperatures are warmer than -5 degrees Celsius ice crystals join together a become bigger clumps

Sleet, glaze and hail

Sleet is small particles of clear translucent that form from temperatures above freezing overlie a subfreezing ground

Glaze is also known as freezing rain but they form when rain drops become super cold as they fall through subfreezing air

Hail is produced in the cumulonimbus cloud they are in the shape of small ice pellets that grow as they collect super cooled rain drops