Chapter 12
Section 1
Three types of Meteors
Hydrometeors- consist of cloud droplets and all forms of precipitation
Lithometeors- consist of smoke and haze and dust
Electrometeors- thunder and lightening
Weather vs. Climate
Weather is the current state of the atmosphere (short term)
Climate is the average over a period of time (long term)
Air Masses
There are 5 different types
Continental Tropical- hot and dry; Arizona
Maritime tropical- warm and moist; Southern tip of Florida
Continental Polar- cold and dry; Canada
Maritime Polar- cold and moist; Alaska
Artic- much colder and dry; around the north pole
Air Mass Modification
When an air mass moves to a different area and takes on different characteristics
Weather Systems
Section 2
Global Wind Systems
 Earth rotates from West to East
 The direction of Earth’s winds are influenced by rotation
 Coriolis effect is the movement of fluids and objects in a curved path and not
a straight line
 Curves right in the North and Left in the South
 Global wind systems result from heat imbalance and the Coriolis effect
 They equalize thermal energy on Earth
 3 basic wind systems:
o Polar Easterlies
o Prevailing Westerlies
o Trade Winds
Polar Easterlies
 60 N latitude and north pole
 60 S latitude and south pole
 Cold Winds
 Weak and sporadic
 Polar fronts are areas of stormy weather
Prevailing Westerlies











30 N-60 N
30 S-60 S
Originate in the west
Steady winds that move most weather across the U.S. and Canada
Trade Winds
30 N- 30 S
Two circulation belts
Air sinks, warms, and moves toward the equator in an easterly direction
Once at the equator it moves back north and south
Describe the horse latitudes and the inter-tropical convergence zone
Horse Latitudes- Near 30 N and 30 S latitude; area of high pressure causing
weak surface winds
Inter-tropical Convergence Zone- Near equator; low pressure regions; forms
bands of cloudiness and storms to deliver moisture to rain forests
Jet Streams
 A jet stream is a narrow band of fast westerly wind; the strongest core of
winds
 Polar jet streams
o Separates the polar easterlies form the prevailing Westerlies
Subtropical jet streams
o Located where trade winds meet prevailing Westerlies
o Weather systems usually follow the path of the jet streams
Fronts




4 types of fronts:
o Cold- cold, dense air displaces warm air and forces the warm air
up along a steep front
o Warm- advancing warm air displaces cold air
o Stationary- two air masses meet and neither advances into the
other’s territory. Frequently occurs when two air masses have
become so modified in their travels that the temperature and
pressure gradients between them are small
o Occluded- sometimes when cold air mass moves so rapidly that it
overtakes a warm front. The advancing cold air wedges the warm
air upward.
Pressure Systems
Air always flows from an area of high pressure to an area of low pressure
Low-pressure systems are associated with cloudy weather and
precipitation; air rises; counter- clockwise movement
High-pressure systems are associated with fair weather; air sinks;
clockwise movement