Download 8.10B Weather Maps

8.10B
Weather Maps!
"#$%&'(!)*$+,&-+'.!
© 2011
Rice University – All Rights Reserved
Weather!
Interaction between air masses
brings changes in weather
conditions—
Cold Fronts
and
Warm Fronts
Air Mass Characteristics:
Temperature
Air pressure (high or low)
Humidity
The day-to-day state of the atmosphere
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Rice University – All Rights Reserved
Atmospheric Movement!
Large scale movement of warming and
cooling air distributes thermal energy on
Earth.
The rotation of Earth causes the rising and
sinking air masses to be diverted in
predictable curved directions described as
the Coriolis Effect.
Global air circulation patterns within the
atmosphere held to Earth by gravity and warmed as
heat radiates from Earth; influenced by convection
of warm less dense air (rises and spreads out) and
cold dense air (sinks) !
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Rice University – All Rights Reserved
Air Pressure!
Everyone has felt the force of air
pressure when the wind blows.
Mount Everest (8,850m)
Air pressure is greatest at sea level
and lessens with increased distance
from Earth’s surface; air molecules
are more densely packed at sea level.
© 2011
Atmospheric air pressure is the force exerted
on Earth’s surface by the weight of the air
above the surface
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The mechanism behind the
wall barometer
Barometer
A decreasing barometric
pressure signals upcoming
stormy weather.
An increasing barometric
pressure signals fair weather.
An instrument that measures the amount of
atmospheric pressure
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Rice University – All Rights Reserved
!
Air Masses!
Air masses take on properties of temperature and humidity of the underlying
area. These characteristics are fairly uniform throughout the air mass and remain
relatively stable as the air mass moves over the globe.
cA
An air mass forming
over a hot desert
would be dry and
hot. One forming
over a cold marine
surface would be
cold and humid.
An air mass is a body of air extending
over a large area (1,000 miles or more) that develops
and retains specific characteristics of pressure,
temperature, and humidity. !
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Rice University – All Rights Reserved
High-Pressure Air Mass!
HIGHS are denser, cooler, and dryer
than the adjacent air. The air is
descending toward Earth’s surface.
HIGHS bring pleasant weather
conditions in the summer and very cold
clear weather in the winter.
An air mass with greater atmospheric pressure
than the surrounding air masses; air moves
away from the high pressure, traveling in a
clockwise direction!
© 2011
Rice University – All Rights Reserved
Low-Pressure Air Masses!
LOWS bring stormy weather
S
bring stormy
weather.
Source: NASA
Because of the rising air in the center of a LOW,
surrounding air moves toward a LOW. The contact line
where air masses with differing characteristics meet
becomes a warm front or a cold front.
An air mass with less atmospheric pressure than
the surrounding air masses; air moves toward the
low pressure, traveling in a counterclockwise
direction!
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Rice University – All Rights Reserved
Warm Front!
Warm fronts are relatively slow moving and are
characterized by a series of clouds getting lower
and thicker as the front approaches.
Precipitation occurs ahead
of the frontal boundary
and tends to be prolonged
but gentle; local air
temperature changes from
cool to warm after the
front passes.
Forms at the surface of Earth when a warm, moist
air mass overtakes a cool, dense, and dryer air mass!
© 2011
Rice University – All Rights Reserved
Cold Front!
Cold fronts are fast moving with steep frontal boundary
that force the warm air to rise quickly, resulting in rapid
phase changes. Cold fronts are characterized by
dramatic storms, cumulonimbus clouds, thunder,
lightning, and sometimes tornadoes.
Precipitation occurs at the
frontal boundary and
tends to be heavy but of
short duration; local air
temperature changes
from warm to cool after
the front passes.
Forms at the surface of Earth when a cold, dry, air
mass overtakes a warmer, humid air mass !
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Rice University – All Rights Reserved
Weather Map!
Weather maps vary in scale and in the data
used to create them including radar,
satellite, and ground-based
measurements.
Weather maps are valuable tools to
inform about current weather
conditions and to forecast
upcoming weather changes.
http://www.dnr.sc.gov/climate/sco/Education/wxmap/wxmap.php
A weather map or chart shows the
weather conditions at a specific point in time
over a specific region!
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Rice University – All Rights Reserved
Meteorologists!
Specialist who studies the science of Earth’s
atmosphere and the causes of weather conditions
© 2011
Rice University – All Rights Reserved