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

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