Air Masses and Fronts

Air Masses and Fronts

Differences in air pressure are caused by unequal heating of the Earth’s surface with equatorial air receiving more heat and rising (causing low pressure) while the polar regions have sinking cold air (causing high pressure)

Moving Air

From high pressure to low pressure (thus from poles to equator)

Temperature differences create three wind belts per hemisphere

The Coriolis Effect caused by the rotation of the Earth influences air patterns

How Air Moves:

Large body of air throughout which temperature and moisture content are similar

Created by: a stationary body of air that takes on the characteristics of that region

Air Mass:

Classified according to their source region:◦ Polar – forms in cold regions◦ Tropical – forms in warm regions◦ Continental – forms over land and thus dry◦ Maritime – forms over water and thus wet

Air Masses:

Fill out the rest of the chart:

Symbol Air Mass Source Weather

cP      

  Continental Tropical    

    Over cold water  

      Warm and Moist

Filled out chart:Symbol Air Mass Source Weather

cP Continental Polar

Over cold land

Cold and Dry

cT Continental Tropical

Over warm land

Warm and Dry

mP Maritime Polar

Over cold water

Cold and Wet

mT Maritime Tropical

Over warm water

Warm and Moist

Boundaries between air masses; dense cold air does not mix with less dense warm air; do not exist in tropics because no real temperature differences

Fronts:

The front edge of a moving mass of cold air that pushes beneath a warm air mass like a wedge; results in precipitation if warm air mass is humid, severe storms if cold front moves quickly

Cold Front:

The front edge of advancing warm air mass that replaces cold air with warmer air; generally result in precipitation over a large area

Warm Front:

A front of air masses that move either very slowly or not at all, weather similar to warm front

Stationary Front:

A front that forms when a cold air mass overtakes a warm air mass and lifts the warm air mass off the ground and over another air mass

Occluded Front:

Front Description Symbol Diagram

The front edge of a moving mass of cold air that pushes

beneath a warm air mass like a wedge; results in precipitation

if warm air mass is humid, severe storms if cold front

moves quickly

The front edge of advancing warm air mass that replaces

cold air with warmer air; generally results in

precipitation over a large area

 A front of air masses that move either very slowly or not at all, weather similar to a warm front

A front that forms when a cold air mass overtakes a warm air

mass and lifts the warm air mass of the ground and over

another air mass

Front Description Symbol Diagram

Cold

The front edge of a moving mass of cold air that pushes beneath a warm

air mass like a wedge; results in precipitation if warm air mass is

humid, severe storms if cold front moves quickly

WarmThe front edge of advancing warm air

mass that replaces cold air with warmer air; generally results in precipitation over a large area

StationaryA front of air masses that move either

very slowly or not at all, weather similar to a warm front

 none

OccludedA front that forms when a cold air

mass overtakes a warm air mass and lifts the warm air mass of the ground

and over another air mass