Planetary Waves Kinematically Forced by Himalayan Orography

Abstract An analysis is made of the planetary-scale response of the atmosphere to the kinematic effects of orographic forcing by, in particular, the Tibetan Plateau-Himalayan Mountain complex. Theoretical scaling arguments are used to deduce a critical mountain height hc beyond which the component of flow around will dominate that over the orography. The hc is proportional to the meridional scale of the orography and depends on latitude, For north–south scales appropriate for the Himalayas hc ∼ 1.5 km which is much less than the actual height of 3706 m when resolved with tour zonal planetary waves, with the implication that the “around” component will dominate. A steady-state planetary wave model which has a full kinematic nonlinear lower boundary condition is used to simulate the response to the eastern orography whose height has been multiplied by factors ranging from 0.1 to 2.0. Although the mountain configuration was fixed, the locations of the simulated perturbation highs and lows change substantiall...