Contributions to a meteorology of the Tibetan highlands

Summer meteorological conditions in the Tibetan Highlands are evaluated from the analyses of all available surface and aerological data and the detailed examination of NIMBUS and ESSA satellite cloud photographs.Persistent conditionally unstable lapse rates in the middle troposphere over the highlands account for a very high frequency of afternoon cumulonimbus activity which continues into the night in the eastern regions.Wind data show a marked diurnal circulation.The daytime ascending flow over the highlands is maintained during the night about 30,!~of the time by the dominant seasonal component of the regional circulation which is driven by the high tropospheric warm cell even through periods of weak uplift and rainfall.During the summer the Tibetan Highlands act as a heat engine with an enormous convective chimney in the southeastern sector where giant cumulonimbus cells playa major role in continuously carrying heat upward into the high troposphere.This regional circulation is established in the spring when the initiation of the diurnal circulation of the highlands together with the premonsoon rains of NE India, produce a gradual warming of the middle and upper troposphere above the Himalayas.This warming weakens and finally eliminates the subtropical jet stream and establishes the tropical easterly jet.Thus, there is a complex interaction between the formation of the high tropospheric Tibetan anticyclone and the development of the Indian Monsoon.