The Indian Monsoon

ATS 553

Geography Lesson

Indian Subcontinent

Arabian SeaBay of Bengal

Himalayas/Tibetan Plateau

Paki

stanAf

ghan

ista

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Reversal of the Winds

• Most dramatic seasonal reversal of the winds in the world.

Northern Summer Flow @ SFC

Northern Winter Flow @ SFC

SST in the Arabian Sea

SST in the Arabian Sea

Wind Direction:

Notice the shift in direction with the onset of the southwest monsoon.

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SST in the Arabian Sea

Wind Speed:

Notice that the southwest Monsoon (summer) is much stronger than the northeast monsoon.

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SST in the Arabian Sea

Temperature:

Once the southwest monsoon begins, SST begins to fall, despite the fact that it is June!

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SST in the Arabian Sea

Heat Flux:

During the southwest monsoon, heat flux is often negative due to huge amounts of evaporation!

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Positive Feedback in the Winds

• In the Summer:– Continent heats up more than the oceans do.– Strong flow from the ocean towards the land.– Very strong flow results in greater mixing in

the Arabian Sea.– Therefore, SSTs fall—Arabian Sea is actually

COLDER in the summer than it is in the winter!

– Results in even stronger monsoon flow!

Onset/Withdrawal Dates

Monsoon Trough Location

Extremely high temperatures in northern India and Southern Pakistan.

A strong heat low!

Extremely high dewpoints in northern India and Southern Pakistan. Notice Myanmar!

Why is the Southwest Monsoon so much stronger than the Northeast

Monsoon?

To have a strong “winter” monsoon…

• …you need the continent to cool down in the winter.

• Best accomplished by cold air outbreaks from the north.

The Himalayas are in the way!

Seasonality

• In Summer:– The continent heats up a lot.– Feedbacks keep SSTs low.– Southwest monsoon is strong.

• In Winter:– The continent doesn’t cool down all that

much.– SSTs aren’t particularly warm.– Northeast monsoon is weak.

Southeast Asian Monsoon

• Which is why the winter monsoon is so strong in southeast asia!