Impacts of the east-west difference in convective boundary layer height on circulation over the Tibetan Plateau in summer

Based on "The Third Tibetan Plateau Atmospheric Scientific Experiment (TIPEX-Ⅲ)" and the routine meteorological operational sounding data, the European Centre for Medium-Range Weather Forecasts Fifth Generation Reanalysis (ERA-5) data, and the ISCCP cloud cover data during the summers (June, July, and August) of 2013—2015, influences of the east-west difference in the convective boundary layer (CBL) height over the Tibetan Plateau (TP) on synoptic-scale atmospheric circulation are analyzed by statistic and physical diagnosis methods. It is found that the east-west difference in CBL shows an obvious diurnal variation. The CBL is high in the west and low in the east from the noon to the late afternoon, which is mainly attributed to the larger rise of the western CBL height. Corresponding to the large east-west difference in the CBL, temporal change of surface virtual potential temperature displays a "high in the west-low in the east" feature and the change in the western TP (WTP) is larger than that in the eastern TP (ETP). Meanwhile, temperature within the CBL increases in the WTP but slightly decreases in the ETP. Pressure decreases in the CBL but increases in higher levels in the WTP. The anomalous low pressure in the WTP is shallow. At the same time, low-level pressure increases in the ETP. The low-level east-west pressure difference may result in east-west pressure gradient anomaly and anomalous southerly winds over the central TP, which is accompanied by low-level convergence and high-level divergence in the WTP. The shallow low pressure anomaly is favorable for the development of low clouds.