By Josh Pfleger

Adiabatic Temperature Changes and Expansion and Cooling

Temperatures that happen even when heat isn't added or subtracted.

Its caused when air is compressed or able to expand. When air is able to expand it cools, when its compressed it warms.

Orographic Lifting

• Elevated terrains act as barriers to air flow. • As air goes up a slope or mountain, adiabatic

cooling often generates clouds and precipitation.

• As air reaches the leeward side of a mountain, most of its moisture has been lost.

Frontal Wedging

• In Central North America, warm air and cool air collide producing a front.

• The cooler, denser air acts as a barrier over which warm less dense air rises which is called frontal wedging.

Convergence

• Lifting air in the lower atmosphere is called convergence.

• When air flows in from more then one direction it must go somewhere, because it can’t go down, it has to go up.

Localized Convective Lifting

• On summer days, unequal heating of Earth’s surface may cause pockets of air to be warmed more than the surrounding air.

• Rising air of parcels are called thermals• The process that produces rising thermals is

localized convective lifting.

Stability

• If a volume of air was forced to rise, its temperature would drop because of expansion.

• Stable air tends to remain in its first position, while unstable air tends to rise

• Air stability is determined by measuring the temperature of the atmosphere at various heights

• Because stable air resists upward movement, you might conclude that clouds wont form when stable conditions are present in the air.

Condensation

• Condensation happens when water vapor in the air changes to a liquid.

• Examples of condensation could be dew, fog or clouds.

• Air must be saturated for these forms to happen.

Types of clouds

• Three basic types are cirrus, cumulus and stratus

• Cirrus clouds are high, white and very thin. • Cumulus clouds consist of rounded individual

cloud masses. • Stratus clouds are sheets or layers the cover

much or all of the sky.

High clouds

• The three high clouds are cirrus, cirrostratus and cirrocumulus.

• All high clouds are thin and white • These clouds are not considered precipitation

makers

Middle clouds

• Altocumulus clouds are composed of rounded masses that differ from cirrocumulus clouds.

• Clouds that appear in the middle range, from 2000 to 6000 meters, have the prefix alto, as part of there name.

Low clouds

• The three low clouds are stratus, stratocumulus and nimbostratus.

• Stratus clouds are fog like layer of clouds that frequently cover the sky.

• Occasionally these clouds might produce light precipitation.

Clouds of vertical development.

• Some clouds do not fit into any one of the three height categories mentioned.

• Cumulus clouds may grow dramatically under the proper circumstances

• The result often is cumulonimbus cloud that may produce rain showers or a thunderstorm

Fog

• Physically there is no difference between fog and a cloud. The only difference is the method and place of formation.

• Most fog is a result of radiation cooling or the movement of air over a cold surface.

• A blanket of fog is produced in some West Coast locations when warm, moist air from the pacific ocean moves of the cold California current then is carried onshore by prevailing winds

Cold Cloud Precipitation

• The Bergeron process relies on 2 physical processes, which are supercooling and supersaturation.

• Cloud droplets do not freeze at 0 degrees Celsius as expected

• Supercooled water will readily freeze If it impacts a solid object.

Warm Cloud Precipitation

• In warm clouds, the mechanism that forms raindrops is the collision coalescence process

• A lot of the rainfall can be connected with clouds located below freezing level especially in the tropics

• As large droplets move through the cloud, they collide and join together with smaller slower droplets

Rain and Snow

• The term rain means drops of water that fall from a cloud and have a diameter of at least 0.5 millimeters.

• When surface temperature is above four degrees Celsius, snowflakes usually melt and continue their descent as rain before it reaches the ground.

• At temperatures warmer than negative five degrees Celsius, ice crystals join into larger clumps

Sleet, Glaze and Hail

• Sleet is the fall of small particles of clear to translucent ice.

• Glaze results when raindrops become supercooled as they fall through subfreezing air near they ground and turn to ice when they impact the object

• Hail is produced in cumulonimbus clouds

THE END