Thermal adaptation of the large-scale circulation to the summer heating over the Tibetan Plateau

摘要

The potential vorticity equation is employed to diagnose the variation in the large-scale atmospheric circulation in July by using the NCAR/NCEP daily reanalysis data from 1986 to 1995. Based on the theory of thermal adaptation, the schematic diagram of the formation and maintenance of the circulation over the Tibetan Plateau is re- vealed in this paper. The result shows that near the surface of ground is the positive potential vorticity source produced by the increasing diabatic heating with height, which maintains the cyclonic circulation, and that the positive Ertel po- tential vorticity (PV) source is balanced by friction dissipation.