MeteorologyMeteorology

Regents Earth ScienceRegents Earth ScienceSt. Martin de Porres SchoolSt. Martin de Porres School

Mrs. CanfieldMrs. Canfield

Meteorology vs. WeatherMeteorology vs. Weather

MeteorologyMeteorology is the study of atmospheric is the study of atmospheric phenomenonphenomenon

WeatherWeather is the current state of the is the current state of the atmosphere in a given areaatmosphere in a given area

Air MassesAir Masses

An air mass is a large body of air that takes An air mass is a large body of air that takes on the characteristics of the area over which on the characteristics of the area over which it forms.it forms.

Classification of air masses considers Classification of air masses considers whether the air mass is cold or warm, dry or whether the air mass is cold or warm, dry or humidhumid

Classification of Air MassesClassification of Air Masses

cT – continental tropical air mass. Warm cT – continental tropical air mass. Warm and dry. Mexicoand dry. Mexico

mT – maritime tropical air mass. Warm and mT – maritime tropical air mass. Warm and humid. Gulf of Mexico or Caribbeanhumid. Gulf of Mexico or Caribbean

Air masses -- continuedAir masses -- continued

cP – continental polar air mass. Cold and cP – continental polar air mass. Cold and dry. Interior Canada and Alaskadry. Interior Canada and Alaska

mP – maritime polar air mass. Cold and mP – maritime polar air mass. Cold and humid. North Atlantic and Pacifichumid. North Atlantic and Pacific

A – artic air mass. Similar to cP, but much A – artic air mass. Similar to cP, but much colder. North of Canadacolder. North of Canada

See reference tables for more information!See reference tables for more information!

Air masses move because of windsAir masses move because of winds

As air masses move, they are modified by As air masses move, they are modified by the regions over which they movethe regions over which they move

Wind Systems move air massesWind Systems move air masses

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

Convection currents would cause air at the equator to rise and move towards the coolerpoles.

Air at the poles is cooler and denser, so it sinks and displaces warmer tropical air

Rotations of Earth affect windsRotations of Earth affect winds

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

http://whyfiles.larc.nasa.gov/text/kids/Problem_Board/problems/light/images/atmosphere04.gif

http://earthguide.ucsd.edu/virtualmuseum/images/AtlanticGyresWesterliesTradeWinds.jpg

Three major wind systemsThree major wind systems

Trade winds – occur at 30Trade winds – occur at 30oo north and south north and south latitude. Northeast to southwest in the latitude. Northeast to southwest in the Northern hemisphereNorthern hemisphere

Prevailing westerlies – occur between 30Prevailing westerlies – occur between 30oo and 60and 60oo north and south latitude. Circulation north and south latitude. Circulation pattern is opposite that of the trade windspattern is opposite that of the trade winds

Wind systems--continuedWind systems--continued

Polar easterlies – occur between 60Polar easterlies – occur between 60oo latitude latitude and the poles. Circulation is similar to that and the poles. Circulation is similar to that of the tradewindsof the tradewinds

http://gpc.edu/~pgore/Earth&Space/images/globalcirculation.jpg

Winds are affected by temperature Winds are affected by temperature and pressureand pressure

Wind blows from an area of high pressure to Wind blows from an area of high pressure to an area of low pressurean area of low pressure

Pressure is affected by temperaturePressure is affected by temperature– Remember! Heat causes air to expand. This Remember! Heat causes air to expand. This

increases pressure.increases pressure.

Jet StreamsJet Streams

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

Remember!Remember!

Weather systems move from west to east in Weather systems move from west to east in North AmericaNorth America

This related to the prevailing westerlies and This related to the prevailing westerlies and the jet streamthe jet stream

FrontsFronts

A front is a narrow region separating two air A front is a narrow region separating two air masses of different densitiesmasses of different densities

Density of an air mass is related to Density of an air mass is related to temperature, pressure and humiditytemperature, pressure and humidity

http://research.utep.edu/Portals/72/weather%20NOAA/fronts%20vert.GIF

Cold frontsCold fronts

Cold, dense air displaces warm air and Cold, dense air displaces warm air and forces the warm air up along a steep front. forces the warm air up along a steep front.

Usually associated with unstable weatherUsually associated with unstable weather

http://www.pagasa.dost.gov.ph/genmet/fronts/coldfront.gif

Warm frontsWarm fronts

Warm air displaces cold air. Associated Warm air displaces cold air. Associated with cloudiness and precipitationwith cloudiness and precipitation

http://www.pagasa.dost.gov.ph/genmet/fronts/warmfront.gif

Stationary frontStationary front

Two air masses meet and stall. Air between Two air masses meet and stall. Air between the masses does not move.the masses does not move.

Usually involves air masses that have been Usually involves air masses that have been modifiedmodified

Occluded frontOccluded front

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

http://www.coolweather.co.uk/htdocs/fronts.htm

Pressure systemsPressure systems

High pressure– air sinks and spreads away High pressure– air sinks and spreads away from Earth’s surface. It is deflected from Earth’s surface. It is deflected clockwise by the Coriolis effectclockwise by the Coriolis effect

High pressure systems are usually High pressure systems are usually associated with pleasant weatherassociated with pleasant weather

Pressure systemsPressure systems

Low pressure – air rises and is replaced by Low pressure – air rises and is replaced by air from outside the system. air from outside the system.

Low pressure systems are usually Low pressure systems are usually associated with poor weather conditions associated with poor weather conditions

Remember!Remember!

Winds blow in to a low pressure systemWinds blow in to a low pressure system Winds blow away from a high pressure Winds blow away from a high pressure

systemsystem

Weather toolsWeather tools

Thermometer—measures temperatureThermometer—measures temperature Barometer—measures air pressureBarometer—measures air pressure Anemometer—measures wind speed and Anemometer—measures wind speed and

directiondirection Hygrometer—measures humidityHygrometer—measures humidity

Station modelsStation models

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