4.5 Global Wind Patterns

What are the 4 properties air has that determine how it circulates?

1. density

2. water vapor capacity

3. adiabatic heating/cooling

4. latent heat release

Describe air density

mass of all molecules in air in given volume

How do density and temperature determine air movement?

Basically, less dense air rises and denser air sinks. This density difference causes warm air to rise and expand because it is less dense.

How does the ability of air to hold water change with temperature?

With warm air, it is less dense and has a higher capacity for water vapor. This is why hot summer days usually have high humidity because the warm air contains a lot of water vapor.

Define saturation point

max amount of water vapor in air at given temperature

What happens to water vapor in the air if the air temperature drops?

As the temperature drops, the density is denser. This causes the air to fall and have a lower capacity to hold water vapor. Water vapor would condense and turn into rain.

Describe how pressure changes in the atmosphere.

As air rises higher in atmosphere, the pressure decreases. This lower pressure allows the rising air to expand in volume. The expansion lowers the temperature of air.

Define adiabatic cooling

the cooling effect of reduce pressure on air as it rises

Define adiabatic heating

the heating effect of increase pressure on air as it sinks to the surface

Define latent heat release

the release of energy when water vapor in atmosphere condenses into liquid

Describe the effect on the air after latent heat release has occurred

due to the latent heat release, whenever water vapor is the atmosphere condenses, the air will become warmer and rise

Define atmospheric convection currents

global patterns of air movement that are initiated by the unequal heating of Earth

List the steps that occur to produce atmospheric currents

1. hot, dry surface picks up moisture

2. humid air at earths surface rises, pressure decreases as result

3. adiabetic cooling causes air to reach saturation point

4. latent heat release from condensation causes air to expand and rise even higher

5. adiabetic cooling chills air at top

6. cold dry air is displaced

7. adiabetic heating warms dry air that sinks to earths surface

Define Hadley cells

occurs between 0 and 30 degrees. at the equator, these cells start with warm rising air. then, as the air moves away from the equator, the air falls as cooler air.

Trade Winds (east to west).

Define intertropical convergence zone (ITCZ)

the latitude the gets the most intense sunlight which causes hadley cells to converge

Explain why the latitudes of the intertropical convergence zone (ITCZ) are not fixed.

Due to earths rotation, the area getting most intense sunlight shifts

Define polar cells

occurs at latitudes greater than 60. they start around the latitude where warm air from the ferrel cells is pushed up at higher latitude. 

this air cools and falls as dry air on the poles

• Polar Easterlies (east to west).

Define ferrel cells

occurs between 30-60 latitude. around 30 degree latitude line, the cold dry air of hadley cells falls, pushing warm air up

• Westerlies (west to east).

How are Ferrell cells helpful in distributing air in the atmosphere?

allows for adiabatic heating and get back to hot dry air

Define Coriolis effect

the deflection of an objects path due to the rotation of Earth

Looking at the North Pole, what direction does the Earth appear to move, clockwise or counterclockwise?

counterclockwise

Describe why the deflection of objects moving north or south occurs

caused by the Coriolis effect, a result of Earth's rotation on its axis

Why is there a difference in the speed of Earth’s rotation at different latitudes?

because the planet is a sphere, meaning its circumference is widest at the equator and shrinks to zero at the poles

Describe how the atmospheric convection currents and Coriolis effect work together

Atmospheric convection currents initiate global wind movement from high to low-pressure areas, while the Earth's rotation, through the Coriolis effect, deflects these winds to the right in the Northern Hemisphere and the left in the Southern Hemisphere, ultimately creating prevailing wind patterns like the trade winds and jet streams

List each of the prevailing wind patterns and their direction of movement in each latitude section.

• Tropical Latitudes (0° to 30° North and South)

  • Wind Pattern: Trade Winds.

  • Direction: Winds blow predominantly from east to west.

  • Cause: Warm air rises at the equator, moves toward the poles, cools, and sinks around 30° latitude. This forms the Hadley cell, and the resulting surface wind is the Trade Wind.

• Mid-Latitudes (30° to 60° North and South)

  • Wind Pattern: Prevailing Westerlies.

  • Direction: Winds blow from west to east.

  • Cause: This area is influenced by the Hadley Cell (with sinking air at 30°) and the Polar Cell (with rising air at 60°), creating the less direct Ferrel Cell. The surface air within the Ferrel cell flows poleward and eastward.

• High Latitudes (60° to 90° North and South)

  • Wind Pattern: Polar Easterlies.

  • Direction: Cold, dry winds blow from east to west.

  • Cause: Cool air sinks at the poles and travels toward the mid-latitudes, creating the Polar Cell. The surface winds in this cell are the Polar Easterlies.

Rain shadow

A region with dry conditions found on the leeward side of a mountain range as a result of humid winds from the oceana causing precipitation on the windward side