Earth's Atmospheric Circulation, Climate Cycles, and Glacial Processes

Winds

Move because air is pushed from areas of high pressure toward areas of low pressure.

Rising air

Creates low air pressure and usually cloudy/rainy weather.

Falling air

Creates high air pressure and usually dry weather.

Number of circulation cells per hemisphere

3 (Hadley, Ferrel, Polar).

Air at the poles

Falls because cold air is dense, creating high pressure.

Air at the equator

Rises, creating a low-pressure belt (Intertropical Convergence Zone).

Trade Winds

Form as air moves toward the equator, deflected by the Earth's rotation.

Westerlies

Winds that flow from the west in mid-latitudes.

Equator (0° latitude)

Warm and rainy — rising air, low pressure.

30° latitude (North & South)

Warm and dry — descending air, high pressure (desert zones).

60° latitude (North & South)

Cold and rainy — rising air, low pressure (subpolar lows).

Poles (90° latitude)

Cold and dry — falling air, high pressure.

Till

Sediment directly deposited by a glacier; poorly sorted and angular.

Albedo

Fraction of sunlight reflected off Earth's surface; higher during an ice age due to more snow and ice cover.

Glacial and Interglacial periods

Earth alternates between long cold glacial periods and short warm interglacials.

Eccentricity

Changes the distance between Earth and the Sun (shape of orbit).

Obliquity (Axis Tilt)

Affects the seasonal distribution of solar energy.

Precession

Affects the timing of seasonal changes as Earth wobbles on its axis.

Decreased tilt

Causes colder summers and warmer winters.

Glacial impact

Leads to an increase in glacial ice on Earth's surface.