Meteorology, Weather, and Climate

Air Masses, Global Winds and Fronts

Meteorology, Weather, and Climate

is the study of atmospheric phenomena. Meteorology includes weather and climate.

• is the short-term variations in atmospheric phenomena that interact and interfere with the environment and life.

• is the long-term variations of weather in a certain area.

Air Masses

An is a large volume of air that has the same characteristics, such as humidity and temperature, as its source region.

A is the area over which an air mass forms.

Source Regions

Global Wind Systems

The directions of Earth’s winds are influenced by Earth’s rotation.

This results in fluids and objects moving in an apparent curved path rather than a straight line.

The directions of Earth’s wind systems, such as the and the , vary with the latitudes in which they occur.

Polar Easterlies

The polar easterliesare the wind zones between and the north pole, and and the south pole.

Prevailing Westerlies

The prevailing westerlies are the wind systems on Earth located between latitudes , and .

Trade Winds

Between latitudes are two circulation belts of wind known as the trade winds.

Near latitudes 30 N and 30 S, the sinking air associated with the trade winds creates an area of . This results in a belt of weak surface winds called the horse latitudes.

Trade winds from the North and the South meet and join near the equator.The air is forced upward, which creates an area of pressure.

This process, called , can occur on a small or large scale. Near the equator, it occurs over a large area called the intertropical convergence zone (ITCZ).

Jet Streams

A jet streamis a narrow band of , , wind.

in the middle latitudes is strongly influenced by fast-moving, high-altitude jet streams.

Types of Jet Streams

The major jet streams, called the polar jet streams, separate the from the prevailing westerlies.

The minor jet streams are the subtropical jet streams. They occur where the meet the prevailing westerlies.

Fronts

There are four types of fronts:

Cold Fronts

Cold Fronts occur when air displaces air forcing it up along a steep slope. This collision results in .

Warm Fronts

Warm fronts occur when advancing air displaces air developing a gradual boundary slope. Often causes widespread .

Stationary Front

Stationary Fronts occur when two air masses meet but advances resulting in light .

Occluded Front

Occluded fronts occur when a air mass moves so rapidly that it overtakes a front forcing the warm air . are common along an occluded front.

Label the fronts in the diagram below.

Pressure Systems

In the northern hemisphere, winds move counterclockwise around a -pressure center, and clockwise around a -pressure center.