4. Illustrate the role of the Tibetan plateau in the Indian Monsoon.
भारतीय मानसून में तिब्बती पठार की भूमिका का वर्णन करें।
Indian monsoon is a complex system characterized by seasonal reversal in wind direction in south and South East Asia. Monsoon system is modified trade winds guided by various landforms such as Himalayas and water systems such as Pacific. Tibetan plateau especially has very major role to play in genesis of monsoon.
Landforms play a major role in deciding the path of propagation as well as intensity of rainfall, as most of the rainfall in India is orographic in nature. The Himalayas plays a major role in genesis of monsoon as well as monsoon breaks. Tibet Plateau is an enormous block of a high ground act as a formidable barrier as well as a heat source.
Role of the Tibetan plateau in the Indian Monsoon
- Tibetan Heating creates a low pressure in summer which gets coupled with Massacarene High pressure area and thus helps in initiation of Monsoon.
- The vast mountain range also acted as a tall barrier, preventing cold, dry air in the northern latitudes from entering the subcontinent and subduing the warm, moisture-laden winds from the oceans that drive the monsoon.
- During southwest monsoon, a thermal anticyclone appears over Tibet, which the resultant formation of dynamic anti-cyclogenesis. On the south side of the anticyclone, the tropical jet stream is from. The plateau accents the northward displacement of the jet stream in the middle of the October. The withdrawal sub-tropical westerly jet stream to the north Himalayas marks the onset of monsoon season in India.
- With the Tibetan heating and ENSO acting independently of each other, the two factors taken together could have predictive value for rainfall in the monsoon’s early and late phases.
- The tropical easterly jet stream is formed at an eastern longitude of India then moves towards westwards across India and the Arabian Sea to eastern Africa. This upper-level easterly jet stream creates a flow of air on the south side of Tibetan Plateau that reaches down to low levels over northernmost India. During summer, the insolation heating of air above Tibet Plateau weakens the western subtropical jet stream south of the Himalayas with the resultant reversal of pressure gradient and wind flow over northern India.
Thus the presence of Tibet Highland is very important, even if there is no significant barrier effect on the flow of air.