Thermal CirculationThermal Circulation

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Dr. Robert M MacKayDr. Robert M MacKay

Clark College Physics & Clark College Physics & MeteorologyMeteorology

A tale of two identical A tale of two identical citiescities

The air above City 1 cools and that The air above City 1 cools and that above City 2 warmsabove City 2 warms

Air pressure aloft is High above City Air pressure aloft is High above City 22

Winds aloft blow from city 2 to city Winds aloft blow from city 2 to city 1.1.

Examples of Thermal Examples of Thermal CirculationsCirculations

Sea Breeze during the day

Land Breeze at night

South East Asian MonsoonVery dry

South East Asian Monsoon

Very wet

Mountain or Valley breeze??

Upward motion of Valley breeze made visible by clouds

Sea breeze convergence zone in Florida giving rise to very frequent thunderstorms. Florida has more thunderstorms each year than anywhere else in the US.

Stepped Art

Fig. 9-25, p. 241

Local WindsLocal Winds

• Santa Anna WindsSanta Anna Winds– Warm dry that blows from east or Warm dry that blows from east or

northeast don canyons into S. Californianortheast don canyons into S. California– Very fast, desiccates vegetation, Very fast, desiccates vegetation,

providing fuel for firesproviding fuel for fires

• Desert windsDesert winds– Dust storms, sand storms, dust devil, Dust storms, sand storms, dust devil,

haboobhaboob