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U. S. Naval Sea Cadet Corps
Marathon Division
BASIC
METEOROLOGY
© 2004 Marathon Division
OBJECTIVES
• Teach basic weather terminology
• Teach the importance of weather and
forecasting
• Teach a basic understanding of how
the elements of weather interact with
each other
What is “Meteorology”?
The study of weather and
the elements of weather
Weather Elements
TEMPERATURE
• Heating of the earth’s atmosphere by
the sun
• Warm air rises / Cool air sinks
• Measured with the thermometer
How the declination of the Sun
relates to temperature
Sun
Earth
How the declination of the Sun
relates to temperature
The sun’s energy is more concentrated
when the sun is directly overhead (a) than
when it is at an angle (b).
(b)
Sun
Earth
(a)
PRESSURE
• Vertical airflow (caused by changes
in temperature) which results in LOW
and HIGH Pressure areas.
• Creates horizontal airflow (wind)
• Measured with a Barometer
• Isobars - lines of equal pressure
Warm Air
RISES
L
Cold Air
SINKS
H
WIND
• “Unequal distribution of heat energy
in the atmosphere”
• Uneven heating of the earth’s surface
• Wind speed measured with an
Anemometer
• Wind direction measured with a Wind
Vane (weather vane)
WIND (cont.)
• Coriolis Effect due to the earth’s
rotation about its axis will skew the
direction about 15 degrees
• Clockwise change - “VEER”
• Counterclockwise change - “BACK”
CLOUDS
• Minute water droplets or ice crystals
suspended in the atmosphere
• Formed by rising warm air masses
• Water vapor condenses forming
water droplets
• Numerous types found in three
layers
CLOUDS (cont.)
•
•
•
•
•
Low level - Cumulus
Mid level - Prefixed with “alto”
High level - Cirrus
Cumulonimbus - Thunderstorms
Valuable tool in forecasting
HUMIDITY &
PRECIPIATATION
• Rain, snow, sleet, fog
• The condensation of water in the
atmosphere
• Rising air mass cools causing the
water vapor to condense into minute
droplets.
• When the droplets get large (heavy)
enough, they fall as rain/snow.
HUMIDITY &
PRECIPIATATION (cont.)
• What is a desert?
• If the equator is the warmest region
on earth, why aren’t deserts found
there?
• What is the largest desert on earth?
FRONTS
• WARM - red line or half circles
• COLD - blue line or points
• OCCLUDED - purple or both symbols
on the same side
• STATIONARY - half circles on one
side, points on the other
WARM FRONT
WARM AIR
COOLER AIR
Warm Front
•
•
•
•
•
•
Increasing clouds out to 600 miles
Decreasing cloud ceiling
Steady rain within 200 miles of front
Barometer dropping
Wind generally out of the southeast
Expect rain and bad weather within
48 hours
PRECIPITATION
Passing of Warm Front
• Intense or heavy rain diminishes and
weather improves
• Partly Cloudy sky
• Wind shift to the Southwest
• Barometer steady or slightly rising
COLD FRONT
WARM AIR
COLD AIR
Passage of Cold Front
•
•
•
•
Cumulonimbus clouds
Weather deteriorates rapidly
Thunderstorms
Wind shift to the NW with passage of
the front
• Weather improves rapidly with rising
barometer
OCCLUDED FRONT
WARM AIR
COLD AIR
COOL AIR
A
B
C
What weather can you expect at each of these positions?