19.2 Pressure Center & Wind

What is a cyclone? It is a center of low pressure. The pressure decreases from the outer isobars towards the center.

What is an anticyclone? It is a center of high pressure. The pressure increases from the outer isobars towards the center.

What is the rotation of cyclones & anticyclones in the Northern Hemisphere? When the Coriolis effect are applied to LOW pressure centers: and counter-clockwise around the low. When the Coriolis effect are applied to HIGH pressure centers: and clockwise around the high.

What is the rotation of cyclones & anticyclones in the Southern Hemisphere? When the Coriolis effect are applied to LOW pressure centers: and clockwise around the low. When the Coriolis effect are applied to HIGH pressure centers: and counter-clockwise around the high.

How does friction affect the flow of cyclones & anticyclones? In either hemisphere, friction causes Air to flow INWARD around a CYCLONE (LOW). Air to flow OUTWARD around an ANTICYCLONE (HIGH).

What kind of weather can be expected from centers of low pressure (cyclones)? Surface convergence (inflow of air) around a cyclone causes an upward movement of air. Rising air is associated with cloud formation and precipitation. Low-pressure centers can produce bad weather in any season.

What kind of weather can be expected from centers of high pressure (anticyclones)? Surface divergence (outflow of air) around an anticyclone causes a sinking of air. Sinking air produces clear skies, no clouds!

Global Temperature Patterns YouTube: Earth Wind Current The sun’s rays are weaker away from the equator causing less warming. The air here is cool. The sun’s rays are stronger near the equator causing more warming. The air here is warm.

Air moves between the equator and the poles. Global Winds Hadley Cells. Air moves between the equator and the poles. Global Winds

What is the Rotating Earth Model of global winds? It creates a convection system of six cells.

Global Winds Remember, winds are named from where they come!!! 60°N Polar Easterlies - From 90°N to 60°N - Deflected to right 60°N Prevailing Westerlies - From 30°N to 60°N - Deflected to right 30°N Easterly Trade Winds - From 30°N to O° - Deflected to right Doldrums 0° Easterly Trade Winds - From 30°S to 0° - Deflected to left 30°S Prevailing Westerlies - From 30°S to 60°S - Deflected to left 60°S Polar Easterlies - From 90°S to 60°S - Deflected to left

What is a Polar Front? A polar front is a stormy boundary where cold air from the Polar easterlies crashes with the warmer air from the Westerlies

Rotating Earth Model

How do continents influence winds? In the Northern Hemisphere, where land masses break up the ocean surface: Land masses disrupt wind patterns creating Monsoons.

What is a monsoon? Monsoons are the seasonal reversal of wind direction associated with large continents, especially Asia. In winter, the wind blows from land to sea. In summer, the wind blows from sea to land. India experiences a flow of warm water-laden air from the Indian Ocean. YouTube: Wind Patterns YouTube: Monsoon Simulation

What are Local Winds? The local winds are caused either by variations in temperature above land and water (sea & land breezes) topographic effects (valley & mountain breezes)

Sea Breeze Occurs during the day Air moves from the sea During the day, the land heats up & air above it becomes less dense, rises & forms low pressure. During the day, air over the sea is cool. The cool air is more dense, sinks, & forms high pressure.

Land Breeze Occurs during the night Air moves from the land YouTube: Land & Sea Breeze Explained Occurs during the night Air moves from the land During the night, the land cools quickly & the dense air above sinks creating high pressure. During the night, the sea stays warm & the less dense warm air above it, rises creating low pressure.

Valley Breeze Occurs during the day Air moves from the valley UP the slope During the day, the air heats up along the slopes more intensely than the air over the valley floor. This less dense warmer air glides up the slope.

Mountain Breeze Occurs during the night Air moves from the mountain DOWN the slope During the night, the air cools along the slopes more quickly than the air over the valley floor. This more dense cooler air glides down the slope.

What are Prevailing Winds? Wind that blows more often from one direction than from any other. In the United States, the Westerlies consistently move weather from west to east across the continent.