CLOUDS AND PRECIPITATION

By William Deming

Adiabatic Temperature Changes and expansion and cooling

When heat isn’t added or subtracted, they result in being compressed or expanding

Air expands as you elevate your position in the atmosphere

Air expands as it cools and air compresses as it warms

Orographic lifting

Elevated terrains act as barriers to air flow

Once air has moved to the leeward side of say a mountain, most of it’s moisture has been lost. This affect is why most areas may be cut off by mountains yet be completely different on both sides. Ex: wet and moist on the windward, and then hot and dry on the leeward

Frontal Wedging

It is When masses of warm air and cold air collide

Cooler denser air acts as a barrier which the warmer less dense air rises over.

Convergence

When ever air in the lower atmosphere flows together

Because the flowing air cannot go down, cloud formations may occur

Localized Convective Lifting

During summer days unequal heating of earths surface may cause small areas of air to be heated up more then the surface it surrounds

This air will move upward since it is heated, helping animals like birds or humans during activities like hang gliding

Stability (Density Differences and stability and Daily Weather)

Stable air resists vertical movement Unstable air rises freely Clouds formed from the forced movement

of this stable air are typically widespread and have little chance of precipitation. Clouds of unstable air typically tower and can cause thunderstorms

Condensation

When water vapor in the air changes into a liquid or a gas turning into a liquid state

Ex: rain, dew, fog, or clouds Occurs when a vapor is cooled or

compressed to its’ saturation limit

Types of Clouds

Cirrus – Clouds in the atmosphere that are shown and are explained as thin wispy strands

Cumulus – More vertical in their development, they have edges that are easily visible

Stratus - Flat and hazy feature less clouds that may produce a drizzle of rain

High Clouds

Ex: Cirrus, Cirrostratus, and cirrocumulus – 6000 meters

Not considered precipitation making clouds

Middle Clouds

Altocumulus – 4000 meters A light snow or drizzle may happen with

these clouds

Low clouds

Stratus, stratocumulus, and nimbostratus – 2000 meters

May produce light precipitation

Clouds of Vertical development

Bases in low height range, but they often reach upwards to the middle or high ranges

Can produce very strong rain showers or thunderstorms

Fog (By cooling and evaporation)

No physical difference between fog and a cloud, just height

Can form on cool nights where earths surface is cooled very fast by radiation . Later in the night a thin layer of air is cooled before dew point and becomes denser, thus fog

Cool air over warm water may evaporate and help create saturation , when this meets cold air, it condenses with warm air below

Cold cloud precipitation (Bergeron process)

The creation of precipitation in the cold mid to upper layer clouds.

Creates cold rain or ice crystals Super cooled water droplets or ice

crystals must be in the cloud together for the BP to occur

Warm cloud precipitation (collision-coalescence process) Water absorbing particles like salt can

remove the water vapor from the air and help create large raindrops

When these droplets move through a cloud, they form together with smaller droplets.

Rain and Snow

Rain – Requires a think layer of the atmosphere that is above freezing and is caused by condensation of water vapors turned into droplets

Snow – Forms in a motion of upward air near a low pressure system where the temperature must be below freezing

Sleet, Glaze, and Hail

Sleet – clear ice formed by a layer of air above freezing temperatures that lays over a subfreezing layer near the ground

Glaze – occurs when freezing rain hits a surface and creates a formation or sheet of ice around or on an object

Hail – A solid precipitation, which forms in strong thunderstorms, mainly ones with very strong updrafts

The End