Understand the cause of wind and how they affect climate WINDS Understand the cause of wind and how they affect climate Chapter 4 Pages 59-67

What is Wind? A wind is a horizontal movement of air across a surface. Vertical movements are currents or updrafts and downdrafts Caused by what???? Heat versus cold!! Relate it to convection cells previously studied!!!

What causes wind? Unequal heating Unequal heating causes pressure differences Cold, heavy air sinks = high pressure Warm, expanding air rises = low pressure Winds blow from high to low

Know that air blows from areas of high pressure to areas of low pressure. The statement is fact. Think: Air inside a balloon Exhaling Air powered pellet gun It is simply fact. High and low pressures in the earth’s atmosphere are responsible for wind P. 59-61

Application - Land Breeze Using your knowledge of wind predict & explain the wind direction below. P. 61 FACT: Water holds heat longer than the land. During the night, sea air is warmer than the air over the land. Air rises over sea Relative Low pressure over sea Land air moves to lower pressure Low Pressure

Land Breeze Night time Cool breeze Off the land

Application - Sea Breeze Using your knowledge of wind predict & explain the wind direction below. P. 61 FACT: Land heats up faster than the water During the day, air over the land is warmer than air over the sea Air rises over land Relative Low pressure over land Sea air moves to lower pressure Cold “Breeze” off the ocean during the day Low Pressure

Sea Breeze Day time Cool Breeze Off the ocean

Define the terms wind & prevailing wind. p.61-63 is a horizontal movement of air across a surface. It results from air masses of different temperatures and humidity lying next to each other. The resulting pressure variation causes “wind” to blow from high pressure areas to low pressure areas. Prevailing Wind: Is regular, predictable, normal wind direction for a given area or region. Caused by global convection cells. Named after the direction from which it comes

Prevailing Winds Lab

Prevailing Winds

Describe how the coriolis force affects wind direction. objects in motion tend to deflect to the right in north hemisphere to the left in south hemisphere Consequently winds: in the northern hemisphere tend to curve to the right of their path. while in the southern hemisphere they deflect left of their path.

Summary of prevailing wind Global highs and lows are due to uneven heating of the earth Air moves from high pressure to low pressure creating winds Winds are deflected in the directions indicated on the diagram due to the coriolis effect.

Make inferences about how winds are related to major pressure belts. p Air rises at the equator It settles at the poles Result = 6 convection cells 3 above and 3 below the equator. Low pressures result where hot air rises. High pressures result where cool air settles

Describe Orographic rainfall p. 66 Leeward Chinook Windward A relatively warm, moist air blows off the sea It is forced up by mountains (high relief) Air cools at higher altitude Cool air holds less moisture Consequently clouds condense and rain falls Most rain falls on the windward side of the relief Leeward side is often in a dry rain shadow because the moisture has all been lost

Definitions Windward The side of the mountain receiving the wind (consequently more precipitation as well) Leeward The side of the mountain sheltered from the wind (consequently receives less precipitation) Rain Shadow The area located on the leeward side of a mountain that receives low amounts of precipitation. Mainly due to the air that descends on the leeward side has “dumped” on the windward side.

Describe Frontal rainfall p. 66 Weather Front-2 fronts meet Hence the name frontal rain FRONT Warm, moist air Warm Moisture laden air meets cold air Warm air is less dense & is forced up over the cooler, more dense air Warm Moisture laden air cools at higher altitude Cool air holds less moisture Consequently clouds condense and rain falls

Describe Convectional rainfall p. 67 Often associated with thunder storms. Air heated from the earth Usually occurs in hot areas like tropics or continental summer Sun heats the earth causing large amounts of water to evaporate Hot air rises forming convection currents (hence the name) Warm Moisture laden air cools at higher altitude Cool air holds less moisture Consequently clouds condense and rain falls

Analyze the relationship between wind systems and temperature. How do the prevailing winds affect temperature in: Argentina Columbia Baffin Island Newfoundland

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Analyze the relationship between wind systems and precipitation How do the prevailing winds affect precipitation in: England Midwestern U.S. British Columbia Northern Africa Central Australia Question #26 p. 67 = great active learning lab

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