Intraseasonal Variations of Summer Convection over the Tibetan Plateau Revealed by Geostationary Satellite FY-2E in 2010–14

Based on the infrared black body temperature (TBB) observed by the geostationary meteorological satellite FY-2E from 2010 to 2014, the seasonal migration, occurrence frequency, and intraseasonal variability of summer convection over the Tibetan Plateau (TP) and its surrounding areas are analyzed. The results show that in May, convection mainly occurs over the eastern edge of the TP; in June, following the onset of the Asian summer monsoon, the strongest (severe) convection occurs in the southeastern part of the TP; and in July–August, strong southwesterly winds transport abundant moisture to the eastern and central areas of the TP, leading to formation of an active convection belt over southeastern TP. The results also show that in the western TP, the area with convection frequency greater than 6% occupies the southern plateau around the 37th pentad, and gradually moves northward until the end of July; in the central plateau, convection (severe convection) becomes active since early (mid) June, and maintains through the entire late summer with three major northward movements until reaching 34°N; and in the eastern TP, the convection is relatively active since the beginning of May and its northward stretching is slightly later than that over the central plateau. Overall, summer convective activities are unevenly distributed over the TP, with frequency of convection decreasing from south to north; and they also exhibit considerable intraseasonal variability, the maximum of which is found over the middle reach of the Yarlung Zangbo River and the southeastern plateau. EOF analysis of summer convection frequency over the TP reveals two leading modes, with the first mode being a dipole variation pattern between the Indian monsoon region and the southeastern TP, and the second mode a tripole pattern over the western TP, the Indian continent west of 80°E, and the South Asian continent east of 80°E.