The atmospheric heat budget over the western part of the Tibetan plateau during Monex, 1979

The atmospheric heat source strength over western Tibet has been computed for the period beginning with the last ten days in May, 1979 and extending through August, 1979. Our results show a significantly smaller heat source than that obtained by other authors. The discrepancy is mainly due to adjustments in the drag coefficient suggested by observations and numerical modeling experiments. We subdivided western Tibet into northern and southern parts. In the north sensible heating,SH, provides the dominant input into the atmospheric heat source, whereas in the southern part latent heat,LP, offers a significant contribution after the start of the rainy season. Detailed heat budget calculations were also carried out over limited regions of southwestern Tibet which had good station coverage. During periods with area-averaged rainfall ⩽1 mm/day an atmospheric heat source maximum was located over southwestern Tibet near the 500 hPa level, while a heat sink dominated the upper troposphere in a layer of subsidence. When rainfall exceeded 4 mm/day, ascending motions and heat sources prevailed throughout the troposphere with maxima near 400 hPa. Time series analyses of the heat source components show that the total atmospheric heat source is strongly modulated by the release of latent heat. Atmospheric radiational cooling reveals a phase shift in its relation with precipitation. During the first part of the observation period a correlation of that cooling exists mainly with the net radiation at the top of the atmosphere, during the last part with the net radiation at the ground.