Meteorology Regents Earth Science St. Martin de Porres School Mrs. Canfield

Meteorology vs. Weather  Meteorology is the study of atmospheric phenomenon  Weather is the current state of the atmosphere in a given area

Air Masses  An air mass is a large body of air that takes on the characteristics of the area over which it forms.  Classification of air masses considers whether the air mass is cold or warm, dry or humid

Classification of Air Masses  cT – continental tropical air mass. Warm and dry. Mexico  mT – maritime tropical air mass. Warm and humid. Gulf of Mexico or Caribbean

Air masses -- continued  cP – continental polar air mass. Cold and dry. Interior Canada and Alaska  mP – maritime polar air mass. Cold and humid. North Atlantic and Pacific  A – artic air mass. Similar to cP, but much colder. North of Canada  See reference tables for more information!

Air masses move because of winds  As air masses move, they are modified by the regions over which they move

Wind Systems move air masses  In theory, convection would cause air to warm and rise at the equator, move north or south as it cools, and sink near the poles.

Convection currents would cause air at the equator to rise and move towards the cooler poles. Air at the poles is cooler and denser, so it sinks and displaces warmer tropical air

Rotations of Earth affect winds  Coriolis effect —Particles in the Northern hemisphere is deflected to the right. Particles in the Southern hemisphere is deflected to the left. This is due to the rotation of Earth.

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Three major wind systems  Trade winds – occur at 30 o north and south latitude. Northeast to southwest in the Northern hemisphere  Prevailing westerlies – occur between 30 o and 60 o north and south latitude. Circulation pattern is opposite that of the trade winds

Wind systems--continued  Polar easterlies – occur between 60 o latitude and the poles. Circulation is similar to that of the tradewinds

Winds are affected by temperature and pressure  Wind blows from an area of high pressure to an area of low pressure  Pressure is affected by temperature –Remember! Heat causes air to expand. This increases pressure.

Jet Streams  Jet streams are caused by the differences in temperature and pressure that exist between surface and upper level air

Remember!  Weather systems move from west to east in North America  This related to the prevailing westerlies and the jet stream

Fronts  A front is a narrow region separating two air masses of different densities  Density of an air mass is related to temperature, pressure and humidity

Cold fronts  Cold, dense air displaces warm air and forces the warm air up along a steep front.  Usually associated with unstable weather

Warm fronts  Warm air displaces cold air. Associated with cloudiness and precipitation

Stationary front  Two air masses meet and stall. Air between the masses does not move.  Usually involves air masses that have been modified

Occluded front  A warm air mass is squeezed up between two cold air masses. It gets stuck up on top

Pressure systems  High pressure– air sinks and spreads away from Earth’s surface. It is deflected clockwise by the Coriolis effect  High pressure systems are usually associated with pleasant weather

Pressure systems  Low pressure – air rises and is replaced by air from outside the system.  Low pressure systems are usually associated with poor weather conditions

Remember!  Winds blow in to a low pressure system  Winds blow away from a high pressure system

Weather tools  Thermometer—measures temperature  Barometer—measures air pressure  Anemometer—measures wind speed and direction  Hygrometer—measures humidity

Station models  Station models are used to depict the data collected at a weather station