Tropical to subtropical circulation

Major Zones ITCZ (Intertropical convergence zone) Subtropics (30 degrees, north/south hemisphere) Front Poles

Hadley Cells Giant tropical circulation pattern Partially driven by convective processes along the ITCZ

Hadley Cell Products Heavy rainfall with in the ITCZ Major transfer of energy from the ITCZ to higher latitudes –Sensible heat –Latent heat Sets the stage for the dominant pressure cells in the Earth’s atmosphere

Pressure Cells ITCZ –Rising hot air –Creates zones of low pressure Subtropics –Sinking dry air –Creates zones of High pressure

Hadley Cell products continued Subtropics: ↓ condensation and  evaporation –Sahara dessert

Subtropics feed into the Hadley cell Warm dry air (trade winds, N & S) moves through the subtropics and towards the tropics picking water vapor. These warm moist winds meet in the ITCZ and feed the Hadley cell.

The Sun’s role Provides energy to the Hadley cell So, if the energy from the sun changes so does the strength of the Hadley cell and the location of the ITCZ –Summer, N (June-September), ITCZ shifts north –Summer, S (December-March), ITCZ shifts south

Monsoons

Monsoon circulation

Atmospheric circulation at middle and high latitudes

The movement of air from mid to high latitudes Areas above 35 degrees latitude Air typically moves from areas of high pressure to areas of low pressure Except……..

Effects on the land in mid latitudes Low pressure cells tend to move fast in a west to east direction in the mid-latitudes Sometimes these cells are forced to move over topographically high areas. –Orographic precipitation