An Observational Study on the Vertical Structure of the Upper Troposphere and Lower Stratosphere in Gaize of Tibet during the Rainy Season

By analyzing three-times-daily radiosonde observation data from the third Tibetan Plateau experiment of atmospheric science during July-August 2014, the vertical structure of the troposphere has been investigated. A temperature inversion layer, which is associated with wind shear and relative humidity decrease, is found at altitudes between 17 and 19km above sea level . The layer average thickness and average temperature lapse rate are about 100m and 0.33 K/(100 m). The height of the first tropopause is approximately 16082 m, a little lower than the height (16466 m) of the second tropopause. The frequency of occurrence of the former is much larger than that of the latter which might result from the rare occurrence of jet streams and both are inversely correlated with temperature and pressure at the level of the tropopause. The maximum wind speed (08:00,14:00 and 20:00, Beijing time) is 16.2, 16.3 and 15.9 m/s respectively at altitudes of 11.8, 12.6 and 12.1 km, while the wind direction changes clockwise from southwesterly winds in lower levels to southeasterly winds in upper levels in response to the warm advection. The wind direction finally turns to northeasterly above 17 km height. The relative humidity increases significantly with altitude from ground until about 8 km above ground level (AGL), where RH reaches its peak value and then decreases with increasing altitude. Also, the RH inversion can be observed in lower levels.