Weather Systems SWBAT describe how the rotation of Earth affects the movement of air; compare and contrast wind systems; identify the various types of fronts.

Global Wind Systems Coriolis effect The rotation of earth causes particles such as air to be deflected to the right in the northern hemisphere and to the left in the southern hemisphere

With a partner In your own words describe how the rotation of Earth affects air movement. The Coriolis effect causes air molecules to be deflected to the right in the northern hemisphere and the left in the southern hemisphere. This, along with the imbalance of heating due to the angle sunlight strikes the earth, creates distinct global wind systems that transport warmer air to colder areas and vice versa. The result is a balancing of heat energy on Earth.

Global Wind Systems Trade winds Occur at 30° north and south latitude. Air sinks, warms and moves toward the equator in a westerly direction. When the air reaches the equator it rises again and moves back toward 30° latitude, where the process starts again. At 30° latitude there is a high pressure belt that causes weak face winds. At the equator there is a low pressure zone called the intertropical convergence zone

Global Wind Systems Prevailing Westerlies These winds flow between 30°N and 60°N as well as 30°S and 60°S. They flow in a pattern opposite to the trade winds, with surface winds blowing toward the poles in a generally easterly direction. These are responsible for the weather in the US.

Global Wind Patterns Polar Easterlies These winds lie between 60°N and S and the respective poles. They are similar to the trade winds, flowing from northeast to southwest in the northern hemisphere, and southeast to northwest in the southern hemisphere. They are characterized by their cold air.

Global Wind Patterns Jet streams Narrow bands of fast, high altitude, westerly winds. They can flow up to 185 km/h. How does the jet stream affect weather? Jet streams cause disturbances, creating large scale weather systems. It affects the intensity of weather by moving air of different temperatures from one region to another.

In groups of 2-3 You will create a model of a globe that illustrates the global wind patterns we have studied . You must mark the following latitudes on your globe: Equator = 0° Horse latitudes = 30°N and 30°S 60°N and 60°S Poles = 90°N and 90°S Also label the northern and southern hemispheres You must include: Trade winds pattern Prevailing westerlies pattern Polar easterlies pattern Coriolis effect Intertropical Convergence Zone Polar jet stream Subtropical jet stream

Fronts Front The narrow region separating two air masses of different densities (caused by differences in temperature, pressure, and humidity)

Front Types Cold front Cold dense air displaces warm air and forces it upward in a steep front. Clouds, showers, and thunderstorms are associated with cold fronts. It’s represented on a weather map by a solid blue line with blue triangles pointing in the direction of the front.

Front Types Warm Front Advancing warm air displaces cold air. Due to the slow movement of the cold air it develops a gradual slope. It’s characterized by extensive cloudiness and precipitation. It’s represented on a weather chart by a solid red line with semicircles facing in the direction of the front’s movement.

Front Types Stationary Front When 2 air masses meet and neither advances into the other’s territory the boundary stalls. They seldom have clouds or precipitation, but can be similar to the weather of a warm front. It’s represented on a weather chart by a combination of warm and cold fronts symbols.

Front Types Occluded Front Occurs when a cold air mass moves rapidly and overtakes a warm front. The cold air wedges itself under the warm air, forcing it upward. When it forces the warm out of the way it collides with another cold front. Precipitation is common on both sides of an occluded front. It’s represented on a weather map with an alternating line of purple triangles and semicircles

Pressure Systems Describe and illustrate air movement in a high pressure system. Air sinks and then spreads away from the center. It moves in a clockwise direction in the northern hemisphere and counterclockwise in the southern, due to the Coriolis effect. Associated with fair weather. H

Pressure Systems Describe and illustrate air movement in a low pressure system. Air rises from the surface and is replaced by air from outside the system pulling it toward the center. It moves in a counterclockwise direction in the northern hemisphere and a clockwise direction in the southern hemisphere. Associated with clouds and precipitation. L

With a partner Answer questions 1-6, on page 311. Be sure to answer in complete sentences. If you don’t finish in class you must complete this for homework.