青藏高原南侧大气热源对江淮流域南北偶极型降水季节内振荡的调节OACSTPCD

On the basis of the station-based daily precipitation in China from 1979 to 2018 and the atmospheric fields from Japanese 55-year Reanalysis(JRA-55),this paper analyzed the characteristics of the 10-30-day Intra-seasonal Oscillation(ISO)of the north-south dipolar precipitation in the Yangtze-Huaihe Valley(YHV)in summer.In particular,the modulation of the atmospheric heat source over the southern Tibetan Plateau(TP)with different intensity was investigated on the peak and trough of ISO of the north-south dipolar precipitation in the YHV.It is found that strong(weak)heating over the southern TP induces enhanced floods(drought)in the southern YHV and drought(floods)in the northern YHV.The anomalous strong heating over the southern TP intensifies the anomalous warm low in the lower troposphere,with the pumping effect favorable to the water vapor from Bay of Bengal converging towards TP.Meanwhile,the converging and upward motion over the southern TP induces upper-level divergence.Thus,the anomalous anticyclonic circulation in the westward propagating Eurasian wavetrain is enhanced and expanded southward when reaching the northwestern TP,further strengthening the upper-level divergence,the water vapor transport in the low troposphere is strengthened,and the sufficient water vapor supply in the southern YHV leads to the enhanced precipitation.Moreover,the inhomogeneous meridional distribution of the adiabatic heating,i.e.,positive over the southern TP and negative over the Bay of Bengal,results in genesis of the anomalous negative vorticity source and enhancement of water vapor from the periphery of anticyclonic circulation over the Bay of Bengal converging to TP and then veering towards the YHV.It is on the contrary when the anomalous heating over the southern TP is weak.