Types of monsoons

Types of monsoons

Monsoons are seasonal reversals of wind direction that affect the Indian sub-continent and are caused by the following factors:

  1. Extreme heating and cooling of large land masses in relation to the surrounding sea, which impacts on pressure and winds.
  2. The Himalayas that are high enough to interfere with general atmospheric circulation.
  3. Movement northwards of the ITCZ in summer in the northern hemisphere.

The ITCZ shifts northwards as the sun is overhead at the Tropic of Cancer. Insolation over Northern India increases, causing air to rise and creating low pressure. Equatorial maritime (Em) and Tropical maritime (Am) air is drawn north and diverted northeast due to the Coriolis force. The humid unstable air results in rainfall. Amounts are increased as air is forced aloft over the Himalayas and Western Ghats. The rainfall is vital for the cultivation of rice.

Types of monsoons

Winter monsoon

Low temperatures over central Asia create areas of high pressure, at the same time, the sub-tropical jet and ITCZ shift south. Air moving out from the area of high pressure is very dry and becomes drier as it crosses over the Himalayas, causing clear skies and sunny weather over most of India from November to May.

Types of monsoons

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