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Monsoon Meteorology. ATS 553. Monsoon:. A reversal of the wind direction at the surface, usually accompanied by the change in the precipitation regime, that occurs in the tropics on a seasonal time scale. Caused by:.
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Monsoon Meteorology ATS 553
Monsoon: • A reversal of the wind direction at the surface, usually accompanied by the change in the precipitation regime, that occurs in the tropics on a seasonal time scale.
Caused by: • …the fact that water takes so much longer to heat up or cool down than land does.
Therefore… • In the SUMMER hemisphere, tropical land masses are much hotter than the surrounding ocean. • In the WINTER hemisphere, tropical land masses are much colder than the surrounding ocean. • Formation of HEAT LOWS and POLAR HIGHS:
Heat Lows 500mb 700mb 850mb 1000mb
Heat Lows 500mb 700mb 850mb 1000mb
Heat Lows 500mb 700mb 850mb 1000mb
Heat Lows 500mb 700mb 850mb 1000mb
Heat Lows 500mb 700mb 850mb 1000mb L
Heat Lows 500mb 700mb 850mb 1000mb L
Polar Highs 500mb 700mb 850mb 1000mb
Polar Highs 500mb 700mb 850mb 1000mb
Polar Highs 500mb 700mb 850mb 1000mb
Polar Highs 500mb 700mb 850mb 1000mb
Polar Highs 500mb 700mb 850mb 1000mb H
Polar Highs 500mb 700mb 850mb 1000mb H
Polar Highs 500mb 700mb 850mb 1000mb H
Monsoon Regions Major shift or reversal of the circulation features.
Monsoon Regions Prevailing wind isn’t just a statistical average—it reflects the real flow in the atmosphere.
Monsoon Regions The prevailing wind needs to be reasonably robust.
Monsoon Regions Monsoons are NOT just a shift in the storm track, bringing sequences of highs and lows.
Fig 6-28 in Ramage • India IND • West Africa WAFR • East Africa EAFR • Southeast Asia SEASIA • Australia AUS
Where don’t monsoons happen? • South America • 1. Cold upwelling means that the land is ALWAYS warmer than the surrounding oceans.
Where don’t monsoons happen? • South America • 2. SAMER is too narrow at subtropical southern latitudes for a planetary scale anticyclone to form.
Where don’t monsoons happen? • South America • 3. In the NH, SAMER doesn’t extend to regions of subsidence (which favor heat low formation).
Where don’t monsoons happen? • Mexico, SW US • 1. No region has a 120° wind shift
Where don’t monsoons happen? • Mexico, SW US • 2. Central America is too narrow for formation of polar highs.
Where don’t monsoons happen? • Mexico, SW US • 3. Weather is more driven by synoptic disturbances. However, a monsoon trough does form over the eastern Pacific..
Historically… Grain Coast Ivory Coast Gold Coast Slave Coast