air masses, global winds, and fronts · 2013-02-28 · global wind systems trade winds trade winds...
TRANSCRIPT
Air Masses, Global Winds,
and Fronts
Meteorology is the study of atmospheric phenomena. Meteorology includes weather and climate.
• Weather is the short-term variations in atmospheric phenomena that interact and interfere with the environment and life.
• Climate is the long-term variations of weather in a certain area.
Meteorology, Weather and Climate
An air mass is a large volume of air that has the same characteristics, such as humidity and temperature, as its source region.
A source region is the area over which an air mass forms.
Air Masses
Source Regions
Tropical
Polar
Arctic
Continental
Maritime
Global Wind Systems
The directions of Earth’s winds are
influenced by Earth’s rotation.
This Coriolis effect results in fluids and
objects moving in an apparent curved path
rather than a straight line.
Global Wind Systems
The directions of Earth’s wind systems, such as the polar easterlies and the trade winds, vary with the latitudes in which they occur.
Global Wind Systems
Polar easterlies
The polar easterlies are the wind zones between 60 N latitude and the north pole, and 60 S latitude and the south pole.
Prevailing westerlies
The prevailing westerlies are the wind systems on Earth located between latitudes 30 N and 60 N, and 30 S and 60 S.
Global Wind Systems Trade winds
Between latitudes 30 N and 30 S 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 high pressure. This results in a belt of weak surface winds called the horse latitudes.
Global Wind Systems Trade winds
Trade winds from the North and the South meet and join near the equator. The air is forced upward, which creates an area of low pressure.
This process, called convergence, can occur on a small or large scale. Near the equator, it occurs over a large area called the intertropical convergence zone (ITCZ).
Global Wind Systems
Global Wind Systems
Jet Streams
A jet stream is a narrow band of fast, high-altitude, westerly wind.
Weather in the middle latitudes is strongly influenced by fast-moving, high-altitude jet streams.
Jet Streams
Types of jet streams
The major jet streams, called the polar jet streams, separate the polar easterlies from the prevailing westerlies.
The minor jet streams are the subtropical jet streams. They occur where the trade winds meet the prevailing westerlies.
There are four types of fronts:
Cold Front
Warm Front
Stationary Front
Occluded Front
Fronts
Cold Fronts occur when cold, dense air
displaces warm, less dense air forcing it up along
a steep slope. This collision results in intense
precipitation and sometimes thunderstorms.
Cold Fronts
Warm fronts occur when advancing warm air
displaces cold air developing a gradual boundary
slope. Often causes widespread light
precipitation.
Warm Fronts
Stationary Fronts occur when two air masses
meet but neither advances resulting in light
winds and precipitation.
Stationary Fronts
Occluded fronts occur when a cold air mass
moves so rapidly that it overtakes a warm front
forcing the warm air upward. Strong winds and
heavy precipitation are common along an
occluded front.
Occluded Fronts
Cold Front
Occluded Front Stationary Front
Warm Front
Pressure Systems
In the northern hemisphere, winds move counterclockwise around a low-pressure center, and clockwise around a high-pressure center.
Low-pressure center High-pressure center