During monsoon season the ITCZ (inter tropical convergence zone) shifts almost upto 25
degree North latitude over the Indian subcontinent while it rarely crosses 15 degree North latitude
in other regions. This is because
1. Vast landmass of Eurasia located to the North of the Equator.
2. Intense low pressure over the Northwestern region of Indian subcontinent and over the
vast, high altitude Tibetan plateau pulls ITCZ Northwards.
3. Shifting of Westerly jet streams to the North of Tibetan plateau at the end of the month of
May.
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Explanation:
Inter tropical convergence zone is termed as a thermal equator and is the zone where the Northeast
and Southeast trade winds meet. This ITCZ shifts Northwards upto 25 degree North latitude during
the months of June-July. This is facilitated by all the above points mentioned.
Westerly jet streams: These shifts southward during winters because of the southern shift of entire
pressure belts by some 10 degree latitudes which is in turn because of Southern shift of Sun towards
Tropic of Capricorn during winters. These jet streams because of vast Tibetan plateau,get bifurcated
into 2 parts, with one part traversing south of Himalyan mountains and the other to the north of
Tibetan plateau. With the advent of summers and gradual shift of Sun towards Tropic of Cancer, the
part of the jet streams to the South of Himalayas gets weakened. At the end of the month of May
the Westerly jet streams completely shifts to the North of Himalayas and thus becomes stronger
over the Central China and also Japan. This Northern shift facilitates the Northward shift of ITCZ.