Adiabatic Temperature Changes and Expansion and Cooling • The slower rate of cooling caused by the addition of latent heat is called the wet adiabatic rate, and the rate of cooling or heating applies to unsaturated air and is called the dry adiabatic rate. • When air is allowed to expand, it cools, and when it is compressed, it warms. • The amount of latent heathttp://apollo.lsc.vsc.edu/classes/met130/notes/chapter6/adiab_cool.html released depends on the quantity of moisture present in the air.
Orographic Lifting • When elevated terrains, such as mountains, act as barriers to air flow, orographic lifting occurs. • By the time air reaches the leeward side of a mountain, much of its moisture has been lost. • Many of the rainiest places on Earth are located on these windward mountainhttps://earthscience-in-the- slopes.nationalparks.wikispaces.com/Death+Valley
Frontal Wedging• In central North America, masses of warm air and cold air collide, producing a front.• Weather-producing fronts are associated with specific storm system called middle- latitude cyclones.• The cooler, denser air acts as a barrier over which the warmer, less http://www.harding.edu/lmurray/113_files/HT dense air rises. ML/d2_Earth%20Revised/sld046.htm
Convergence• Convergence can cause cloud development and precipitation.• The pattern of air movement and the uplift that results is helped along by intense solar heating of the land.• Convergence is whenever air in the lower atmosphere flows together, lifting https://commons.wikimedia.org/wiki/File:Oce results. anic- continental_convergence_Fig21oceancont_itali an.svg
Localized Convective Lifting • Unequal heating of Earth’s surface may cause pockets o air to be warmed more then surrounding air. • Rising parcels of warmer air are called thermals. • Birds, such as hawks and eagles, use thermals to carry them to great heights.http://www.richhoffmanclass.com/chapter4.html
Stability • Stable air tends to remain in its original position, while unstable air tends to rise • When air temperature actually increases with height, it is called temperature inversion. (an inversion is created because the ground and the air immediately above the ground will cool more rapidly than air higher above the ground. • When stable air is forced above Earth’s surface, the clouds that form are widespread and have little vertical thickness.http://deved.meted.ucar.edu/marine/mbl/print.htm
Condensation• Condensation happens when water vapor in the air changes to a liquid.• For any of these forms of condensation to occur, the air must be saturated.• When condensation occurs in the air above the ground, tiny bits of particulate matter, called condensation nuclei, serve as http://www.weatherquestions.com/What_is_c surfaces for water- ondensation.htm vapor condensation.
Types of Clouds • Clouds are classified on the basis of their form and height. • There are three cloud groups- Cirrus, Cumulus, and Stratum.http://eo.ucar.edu/webweather/cloud3.html
High Clouds• Three types of clouds make up the high cloud family- Cirrus, Cirrostratus, and Cirrocumulus.• All high clouds are thin and white and often made up of ice crystals.• High clouds are considered to be precipitation makers.http://scienceprep.org/clouds.htm
Middle Clouds • Middle clouds are clouds that appear to be middle range. • They create a uniform white to grayish sheet covering the sky with the sun or moon visible as a bright spot.http://www.odu.edu/~tmmathew/geol442/clo • Infrequent lightuds.shtml snow or drizzle may accompany these clouds.
Low Clouds• There are three members of the low cloud family- Stratus, Stratocumulus, and Nimbostratus.• These clouds are a uniform, fog-like layer that frequently covers much of the sky.• Low clouds are one http://www.scienceinschool.org/print/1940 of the main precipitation makers.
Clouds of Vertical Development • Some clouds do not fit into any of the three categories. • They are all related to one another and are associated with unstable air. • Cumulus clouds that are often connected with fair weather, may grow dramatically under the proper circumstances.http://www.richhoffmanclass.com/chapter5.html
Fog• Fog is defined as a cloud with its base at or very near the ground.• When fog is dense, visibility may be only a few dozen meters or less, making travel difficult and dangerous.• When cool air moves over warm water, enough moisture may evaporate from the water surface to http://www.crh.noaa.gov/jkl/?n=fog_types produce saturation.
Cold Cloud Precipitation • Water in the liquid state below 0 degrees Celsius is said to be “super cooled”. • The Bergon process. • When air is saturated withhttp://www.srh.noaa.gov/lzk/?n=mar2011.ht respect to water,m it is super saturated.
Warm Cloud Precipitation• In warm clouds, the mechanism that forms raindrops is the collision-coalescence process.• Much rainfall can be associated with clouds located well below the freezing level.• Some water- absorbing particles can remove water vapor from the air at relative humiditys https://www.meted.ucar.edu/sign_in.php?go_ less then 100% back_to=http%253A%252F%252Fwww.meted. forming droplets that ucar.edu%252Ftropical%252Ftextbook_2nd_ed ition%252Fnavmenu.php%253Ftab%253D6%2 are quite large. 526page%253D3.0.0
Sleet, Glaze, and Hail • Sleet is the fall of small particles of clear-to-translucent ice. • Hail is produced by Cumulonimbus clouds. • If the ice pellets encounter a strong updraft, they may behttp://www.ksl.com/?nid=367&sid=1150322 carried upward and begin the downward journey once more.
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