Modulation of the Atmospheric Heat Source Over the Tibetan Plateau on the Intra-seasonal Oscillation of Summer Precipitation in the Yangtze-Huaihe River Basin

Abstract

ABSTRACT Based on the daily precipitation from China Meteorological Administration and the daily atmospheric circulation data from the Japanese 55-year Reanalysis (JRA-55) from 1979 to 2018, this paper analyzes the evolution of 10-30-day intra-seasonal oscillation (ISO) of the precipitation in the Yangtze-Huaihe River Basin (YHRB) and the modulation of the atmospheric heat source over the Tibetan Plateau (TP) with different intensity on the peak and trough values of the precipitation in the YHRB. When the atmospheric heating is strong on the southern flank of TP (STP), the lower-level anomalous low strengthens on the STP, which leads to convergence of airflow in the lower troposphere, ascent and divergence in the upper troposphere. Thus, the intense pumping action on the STP results in the convergence of water vapour from the Bay of Bengal to the STP. Due to the high altitude of TP, the water vapour turns eastward and increases the convergence and ascent of water vapour in the YHRB, which is conductive to enhancement of the peak values or weakening of trough values of the ISO of precipitation in the YHRB. When the STP heating is weak, the lower-level anomalous low decreases on the STP, leading to divergence in the lower troposphere, descent and convergence in the upper troposphere. Then the convergence of water vapour from the Bay of Bengal to the STP is suppressed and the transport of water vapour to the YHRB is interrupted, thus the peak values of precipitation are weakened or the trough are enhanced.