What causes winds? Uneven heating between the equatorial poles causes global winds. Since Earth is a sphere AND it is tilted on its axis, the sun’s energy doesn’t evenly reach the earth to equally distribute its heat. Sunlight is concentrated near the equator because it strikes it directly.

What are global winds? The distance wind travels varies. Some winds die out quickly and travel only short distances. Those that travel thousands of miles and last for weeks are called Global Winds Travel in routes called global wind belts. Bill Nye on Wind

If Earth didn’t rotate…. Based on surface temperatures, which area(s) of the Earth would have the HIGHEST Pressure? Which area(s) would have the lowest pressure? Why did you choose these areas? Which direction would the global wind blow?

Winds on a Nonrotating Earth Poles would have cold surface, high pressure Equator would have warm surface, low pressure Winds would simply blow from H to L pressure across a pressure gradient. At surface, air would flow from poles to equator. Once the surface air reaches the equator, what will happen to it? At higher altitudes, air would flow toward poles from equator.

Scenario not likely because…. Earth DOES rotate on its axis and creates the Coriolis Effect. Land and water experience unequal heating.

The Coriolis Effect Only noticeable for winds traveling long distances

Prevailing Winds at the Surface Called Wind Belts High pressure areas create sinking air that flows toward areas of low pressure. Creates three global wind belts in each hemisphere. Coriolis Effect causes winds to curve toward east or west. Named from direction from which they blow.

Prevailing Surface Winds

Trade Winds Blow from the East Move from the 30 ̊ N/S to the equator. (horse latitudes) Strong and steady but die as they reach the equator Created the “doldrums” Inter Tropical Convergence Zone (ITCZ)

Westerlies Blow from the west Move from the horse latitudes toward the poles Bring storms across much of the U.S.

Easterlies Blow from the East Move from polar regions toward the mid-latitudes Stormy weather often occurs when cold air of easterlies meets warm air of westerlies.

Calm Regions Wind belts created earth’s rotation and uneven heating of its surface are separated by calm regions of either a high or low pressure zone. Winds are light and often change direction Doldrums Horse Latitudes

Calm Regions Doldrums-low pressure zone near the equator Warm air rises to top of troposphere and spreads out toward poles Rising moist air produces clouds and heavy rains Heavy evaporation from warm ocean water fuels tropical storms. Horse Latitudes-high pressure zones 30 ̊ N/S of the equator Warm air traveling from the equator cools and sinks here Weather tends to be clear and dry.

Global Circulation Cells 6 Giant Convection Cells are created from earth’s air circulation patterns, and mixture of continents and oceans. Three north of the equator and three south of the equator. Leads to irregular distribution of climates and patterns of vegetation.

Circulation Cells At equator, low pressure zone called equatorial low  abundant precipitation  Rainforests found here. Warm air rises and splits One current moves north One current moves south Both rising parcels are turned by Coriolis Effect toward the East.

Hadley Cells Warm air rising at the equator, moving toward the poles will cool Sinks into a zone of high pressure at the surface near 30° North or South Latitude. Sinking air is dry. Deserts found at 30°N and 30°S of the equator

Hadley Cells At 30° N or S, air near surface flows from high pressure to low pressure toward the equator. From 30° N = Northeast Tradewinds From 30° S = Southeast Tradewinds As it nears the equator air warms and rises again. Creates Hadley Cells at the between equator and 30 °N and 30° S

Midlatitudes-Ferrell Cells At 60°N and 60°S, air is rising from the surface. Warm air rises Creates cool temperate climate with heavy snowfall in winter and cool summers.

At the Poles-Polar Cells At Surface---High Pressure areas: In North, this cold surface air flows toward equator H L. Turned westward by Coriolis Effect As it moves toward lower latitudes (60°N), the air parcel collides with air moving from 30°N and is forced upward. Forms polar cell.