Mechanism of heating and the boundary layer over the Tibetan Plateau

Abstract

The meteorological elements near the plateau surface exhibit pronounced diurnal variations. There is a large ground-air temperature difference during the daytime generating a thin layer of superadiabatic lapse rates near the surface. The horizontal wind speed attains the minimum in the morning and the maximum in the evening. A deep and well-mixed layer of potential temperature is observed over the western and central plateau in the evening (1200 UTC). However, moisture is not well mixed vertically and water vapor mixing ratio is larger in the morning (0000 UTC) than in the evening. The mixed layer becomes shallower from the western to the central plateau and it disappears over the eastern plateau. There is a deep layer of large-scale ascent over the plateau. The upward motion and convective activity over the plateau are more intense in the evening than in the morning. -from Authors