The Indian Monsoon

  • The climate of India is strongly influenced by monsoon winds.
  • The Arab traders who noticed these winds named it as monsoon.

Following facts are important to understand mechanism monsoons –

  1. The differential heating and cooling of land and water.
  2. The Inter-Tropical Convergence Zone (ITCZ) is a broad trough of low pressure in equatorial latitudes where the northeast and the southeast trade winds converge.
  3. The presence of the high-pressure area, east of Madagascar.
  4. The intense heating of Tibetan plateau during summer.
  5. The movement of the westerly jet stream to the north of the Himalayas and the presence of the tropical easterly jet stream over the Indian peninsula during summer.
  • Apart from his changes in the pressure conditions over the southern oceans also affect monsoon.
  • The periodic change in pressure conditions known as ‘Southern Oscillation’ or SO affects monsoon too.
  • El Nino is a warm ocean current that flows past the Peruvian coast in place of the cold Peruvian current, every 2 to 5 years.

The Onset of the Monsoon and Withdrawal

  • The monsoon are pulsating winds affected by different atmospheric conditions encountered by it, on its way over the warm tropical seas.
  • Monsoon arrives at the southern tip of the Indian peninsula generally by first week of June.
  • Sudden increase and continuation of the monsoon for several days is called as ‘burst’.
  • The Arabian Sea and the Bay of Bengal branches of the monsoon merge over the northwestern part of the Ganga plains.
  • The withdrawal or the retreat of the monsoon is a more gradual process which begins in the northwestern states of India by early September.
  • The retreating monsoon or the transition season sees the change from hot rainy season to dry winter conditions.
  • The low-pressure conditions over northwestern India get transferred to the Bay of Bengal by early November causing cyclonic depressions originating over the Andaman Sea.