Monsoon Troughs

ATS 553

TRADE WIND TROUGH:

Northeasterlies and southeasterlies converge near the equator.

Occurs primarily over open oceans.

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HTRADE WIND TROUGH:

Migrates slightly into NH during Northern Summer.

Migrates slightly into SH during Southern Summer.

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HNear Tropical Land Masses:

Subtropical highs and the ITCZ migrate much farther poleward during the local summer season due to heating of the continent.

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HNear Tropical Land Masses:

Subtropical highs and the ITCZ migrate much farther poleward during the local summer season due to heating of the continent.

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A Big Problem:

Notice that the cross-equatorial flow now extends far into the summer hemisphere.

Deflected the wrong way by the Coriolis force!

Should turn opposite direction…

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MONSOON TROUGH

Cross equatorial flow initially has very little deflection either to the left OR to the right.

Then the flow is deflected to the RIGHT (in the NH).

Northeasterlies converge with southwesterlies in the ITCZ.

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MONSOON TROUGH

A defining trait:

There are westerlies EQUATORWARD of the ITCZ!

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BUFFER ZONE

Region of anticyclonic curvature in the flow EQUATORWARD of the ITCZ.

Usually cloud-free.

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HHow this works in the Southern Hemisphere

For a continent in the SH, ITCZ and the subtropical highs migrate far to the south in December-January-February.

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How this works in the Southern Hemisphere

Cross-equatorial flow is deflecting to the right in the SH—WRONG!!!

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HHow this works in the Southern Hemisphere

Instead, at a high-enough southern latitude, low deflects to the LEFT.

MONSOON TROUGH: Southeasterlies converge with northwesterlies.

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HHow this works in the Southern Hemisphere

Notice that once again there are westerlies EQUATORWARD of the ITCZ.

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HHow this works in the Southern Hemisphere

Notice that once again there is a buffer zone EQUATORWARD of the ITCZ.