Monsoons are an important chapter in Geography for the UPSC exam. It is a part of the climate section and is very important since the Indian climate is dominated by this phenomenon. It is also significant for the country’s economy since a large part of Indian agriculture is dependent on monsoons. Hence, the importance of the monsoons for the IAS exam cannot be undermined.
The word ‘monsoon’ is believed to have originated from the Arabic word for season ‘mawsim’. Monsoons are basically seasonal winds that reverse their direction according to the change in season. They are hence, periodic winds. The monsoons travel from the sea to the land in summers and from land to the sea during winters, hence, are a double system of seasonal winds. Historically the monsoons have been very important because these winds were used by traders and seafarers to move from place to place. Though there are monsoon in the Indian subcontinent, central western Africa, Southeast Asia and a few other places, the winds are most pronounced in the Indian subcontinent.
India gets southwest monsoon winds in the summers and northeast monsoons during the winters. The former arise because of the formation of intense low-pressure system over the Tibetan Plateau. The latter arise due to the high pressure cells that are formed over the Siberian and Tibetan plateaus.
Cause: Intense low-pressure formation over the Tibetan Plateau because of intense heating during the summer season; permanent high pressure cell in the South of the Indian Ocean (East to Northeast of Madagascar in summer).
SW monsoon winds bring heavy rainfall to most parts of the country.
Factors influencing onset of SW monsoons:
- Intense low-pressure formation over the Tibetan Plateau
- Permanent high pressure cell in the South of the Indian Ocean
- Subtropical jet stream
- African Easterly jet (Tropical easterly jet)
- Inter-Tropical Convergence Zone (ITCZ)
Factors influencing intensity of SW monsoons:
- Strengths of the low pressure over Tibetan plateau and the high pressure over the south Indian Ocean
- Somali Jet
- Somali Current
- Indian Ocean dipole
- Indian Ocean branch of the Walker Cell
Cause: High pressure cells over the Tibetan and the Siberian Plateaus
NE monsoon winds bring rainfall to the southeast coast of the country (Tamil Nadu coast and Seemandhra’s south coast).
Factors responsible for the formation of the NE Monsoons:
- Formation and strengths of the high pressure cells over the Tibetan and the Siberian Plateaus during winters
- Migration of the Inter-Tropical Convergence Zone (ITCZ) to south of India
- The high pressure cells in the southern Indian Ocean migrating to the west and weakening
|Structure of Atmosphere|
|General circulation of the atmosphere|
|Heating and Cooling of the Atmosphere|