A numerical model study on the behaviour of Asian summer monsoon and AMOC due to orographic forcing of Tibetan Plateau

Simulations using the ECHAM5/MPI-OM coupled atmosphere–ocean model both with and without the Tibetan Plateau are performed in order to study the large scale effects of orographic forcing on the behaviour of the Asian summer monsoon system. Our analysis emphasises the significant impact of plateau forcing on the atmosphere–ocean interactions. It is argued that, in addition to the orographic forcing of the Tibetan Plateau on the climate of Asia such as sensible heat pumping and thermal insulation, other significant direct processes exist, which link the Asian summer monsoon to the sea surface temperatures in the North Atlantic Ocean. The removal of the Tibetan Plateau modifies the wind-driven ocean circulations over the North Atlantic, which leads to a decrease in the surface heat advection over the North Atlantic Ocean and a decrease in the Atlantic Meridional Overturning Circulation. This, in turn, affects, via teleconnections, both the monsoon rainfall and the position of the intertropical convergence zone.