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Unit 8 Notes – Climate Interactions
Weather – The condition of the atmosphere at a specific time and place. Weather changes
from day to day and year to year. Temperature, precipitation, humidity, cloud cover,
barometric (air pressure), and prevailing winds (speed and direction) are examples of weather.
Climate – The average weather conditions of a REGION over a long period of time. The arctic
tundra and a tropical rainforest have distinctive climates, although the weather may change
from day to day. Climates are established by average amounts of precipitation and average
high and low temperatures for an area.
Causes of Weather Systems
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Uneven heating of the earth by the sun
Equator receives MOST solar energy……..the Poles (north and south) receive the least
solar energy
Uneven heating of water and land causes CONVECTION CURRENTS in air and water
Seasons
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Caused by the TILT of the Earth on its axis (imaginary line from north to south pole)
When the Northern hemisphere points TOWARD the sun, it is summer there and winter
in the Southern hemisphere which is pointed away from the sun.
When the Northern hemisphere points AWAY from the sun, it is winter there and
summer in the Southern hemisphere which is pointed toward the sun.
Hurricanes (Typhoons/Cyclones)
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Tropical storms that form over WARM WATER (energy source of hurricane)
Rotate COUNTERCLOCKWISE around a LOW pressure center (eye)
Lose energy as they move over land, away from their energy source (warm water)
Weather Instruments
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Thermometer – measures air temperature
Barometer – measures air pressure
Anemometer – measures wind speed
Psychrometer – measures humidity (water vapor) in the air
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Air Masses
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Large pockets of MOVING air
Distinguished by moisture content and temperature
POLAR – cool or cold air
TROPICAL – warm or hot air
MARITIME – air masses that form over oceans and carry a lot of MOISTURE
CONTINENTAL – air masses that form over land and are DRY with little moisture
4 Types of Air Masses
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Maritime Polar – forms over cold water, moist/cool air, brings moist air and rain
Continental Polar – forms over cold land, dry/cool, brings cold, dry air to an area
Maritime Tropical – forms over warm water, moist/warm, causes hot, humid conditions
Continental Tropical – forms over hot land, very dry/very hot air, brings hot/dry air
Global Winds (Prevailing Winds)
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Blow mostly from a single, general direction over a particular area
Caused by UNEVEN heating of the Earth and Earth’s rotation
Curve due to the CORIOLIS EFFECT
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Coriolis Effect
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The curving of moving objects or AIR from a straight path due to Earth’s
counterclockwise rotation on its axis
Trade winds curve clockwise in the northern hemisphere, and counterclockwise in the
southern hemisphere
o Trade winds – blow EAST to WEST from the equator to 30 degrees latitude
o Westerlies – blow WEST to EAST between 30 degrees and 60 degrees latitude
o Polar Esterlies – blow EAST to WEST from the POLES to 60 degrees latitude and
formed from cold, sinking air moving from the poles.
Jet Streams
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Narrow belts of high speed winds
Blow high up in the atmosphere
Can reach speeds of 500 km/hr
May control the movement of AIR MASSES and STORMS
Air Pressure – Air molecules pressing down on Earth’s surface.
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Air is warmer at the equator and cooler at the poles
DENSITY – PHYSICAL PROPERTY
o Warm air is less dense and RISES, cool air is more dense and SINKS
Air pressure variations cause WIND and WEATHER systems
Measured with a BAROMETER
Rising and sinking air causes CONVECTION CURRENTS in the air - WINDS
High Pressure (blue H on a weather map)
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Cool, dry air mass that is more dense and SINKS toward the surface.
Winds flow CLOCKWISE (anticyclone)
Weather in a high pressure zone:
o Dry conditions
o Light winds
o Fair skies
High pressure flows TOWARD low pressure to EQUALIZE pressure
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Low pressure (red L on a weather map)
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Warm, moist air mass that is less dense and RISES away from surface.
Winds flow COUNTERCLOCKWISE (cyclone)
Weather in a LOW pressure zone:
o Stormy
o Cloudy with precipitation
o Higher winds and wind gusts
Hurricanes are LOW pressure areas formed over warm water
Fronts
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Boundaries between 2 air masses with different temperature, moisture, and pressure
Bring changes in weather as the different air masses try to EQUALIZE the temperature
and pressure between low and high.
Cold Front
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Cold air moving TOWARD warm air
Warm, moist air is forced UP forming clouds that yield rain, wind, and thunderstorms
Usually a FAST moving weather system that quickly clears to cool, dry weather
Shown with a blue line and triangles that point in the direction the front is moving.
Warm Front
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Warm air moving toward cold air
Warm, moist air slides slowly over cold, dense air
Moves more SLOWLY than a cold front
Causes steady rain or snow
Shown by a red line and half-circles that point in the direction the front is moving.
Stationary Front
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Neither air mass is moving very much
Often results in clouds with long periods of precipitation (rain/snow)
Shown by alternating blue (cold) and red (warm) symbols in opposite directions
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