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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.
http://whyfiles.larc.nasa.gov/text/kids/Problem_Board/problems/light/images/atmo
sphere04.gif
http://earthguide.ucsd.edu/virtualmuseum/images/AtlanticGyresWesterliesTradeWind
s.jpg
Three major wind systems
 Trade winds – occur at 30o north and south
latitude. Northeast to southwest in the
Northern hemisphere
 Prevailing westerlies – occur between 30o
and 60o north and south latitude. Circulation
pattern is opposite that of the trade winds
Wind systems--continued
 Polar easterlies – occur between 60o
latitude and the poles. Circulation is similar
to that of the tradewinds
http://gpc.edu/~pgore/Earth&Space/images/globalcirculation.jpg
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
http://research.utep.edu/Portals/72/weather%20NOAA/fronts%20vert.GIF
Cold fronts
 Cold, dense air displaces warm air and
forces the warm air up along a steep front.
 Usually associated with unstable weather
http://www.pagasa.dost.gov.ph/genmet/fronts/coldfront.gif
Warm fronts
 Warm air displaces cold air. Associated with
cloudiness and precipitation
http://www.pagasa.dost.gov.ph/genmet/fronts/warmfront.gif
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
http://www.coolweather.co.uk/htdocs/fronts.htm
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