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8.10B Weather Maps "#$%&’( )*$+,&-+’. Rice University – All Rights Reserved © 2011
8.10B Weather Maps!
"#$%&'(!)*$+,&-+'.!
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Weather!
The day-to-day state of the atmosphere
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Interaction between air masses brings changes in weather conditions—
Cold Fronts and
Warm Fronts
Air Mass Characteristics: Temperature Air pressure (high or low) Humidity
Atmospheric Movement!
Global air circulation patterns within the atmosphere held to Earth by gravity and warmed as heat radiates from Earth; in!uenced by convection of warm less dense air (rises and spreads out) and
cold dense air (sinks) !Rice University – All Rights Reserved © 2011
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 E"ect.
Air Pressure!
Atmospheric air pressure is the force exerted on Earth’s surface by the weight of the air
above the surface Rice University – All Rights Reserved © 2011
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.
Everyone has felt the force of air pressure when the wind blows.
Mount Everest (8,850m)
Barometer !
An instrument that measures the amount of atmospheric pressure
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A decreasing barometric pressure signals upcoming stormy weather.
An increasing barometric pressure signals fair weather.
The mechanism behind the
wall barometer
Air Masses!
An air mass is a body of air extending over a large area (1,000 miles or more) that develops
and retains speci#c characteristics of pressure, temperature, and humidity. !
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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. 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.
cA
High-Pressure Air Mass!
An air mass with greater atmospheric pressure than the surrounding air masses; air moves away from the high pressure, traveling in a
clockwise direction!Rice University – All Rights Reserved © 2011
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.
Low-Pressure Air Masses!
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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S bring stormy weather.
Because of the rising air in the center of a LOW, surrounding air moves toward a LOW. The contact line where air masses with di"ering characteristics meet becomes a warm front or a cold front. Source: NASA
LOWS bring stormy weather
Warm Front!
Forms at the surface of Earth when a warm, moist air mass overtakes a cool, dense, and dryer air mass!
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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.
Cold Front!
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Forms at the surface of Earth when a cold, dry, air mass overtakes a warmer, humid air mass !
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.
Weather Map!
A weather map or chart shows the weather conditions at a speci#c point in time
over a speci#c region!Rice University – All Rights Reserved © 2011
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
Meteorologists!
Specialist who studies the science of Earth’s atmosphere and the causes of weather conditions
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