The Mechanism Of The Synergy Effects Of Tibetan Plateau Heating And Indian Summer Monsoon On Summer Precipitation In Middle Latitudes Of Asia

The geographical scope of middle latitudes of Asia is wide and the impact factors of weather and climate are complex.The Tibetan Plateau(TP)heating and Indian summer monsoon(ISM),as important media linked to middle and high latitudes and tropical systems,have important impact on summer precipitation in middle latitudes of Asia.Previous studies focused on their influence separately,and showed that there was a certain relationship between the two in terms of thermal modes,while the climate effects of different modes still need to be further studied.Based on various precipitation grid data and reanalysis data,this paper mainly investigated the temporal and spatial distribution characteristics of TP heating and ISM in summer by diagnostic analysis method and numerical simulation experiment.The relationship with the summer precipitation in Central Asia(CA)and North China(NC),two typical mid-latitude regions of Asia and the effect mechanism were analyzed.The main conclusions are as follows:(1)In summer,the diabatic heating in TP and its surrounding areas mainly determined by the latent heat released by precipitation.The high value areas are mainly located in the southeastern TP,and the western coast and central of the Indian peninsula.The heating anomaly in Tibetan Plateau-India(TP-IN)region is basically divided into two modes: The“+-” distribution in the southeastern TP and Indian subcontinent and the “+-+" distribution in the southeastern TP,Indian subcontinent and the southern India,and both show obvious interannual variations.(2)The summer thermal configuration of TP-IN region can affect the atmospheric circulation and precipitation in the middle latitudes of Asia.When the first mode is strengthened,there is an obvious wave train in the middle latitude of 500 h Pa.The CA and eastern Asia are occupied by negative anomalies,and positive anomalies are over the Arabian sea,which corresponds to the decreasing precipitation in NC and increasing precipitation in CA.The second mode corresponds to the eastwards shift of the South Asian High.And there are negative anomalies over CA,while positive anomalies over the Bay of Bengal and South Asia.The two thermal modes have different effects on the water vapor transport from the Indian Ocean to inland with two water vapor channels,one from the Arabian sea to northern India and another from the Bay of Bengal to northern India,and then the water vapor continues to spread northward to CA.(3)The Linear Baroclinic Model(LBM)was utilized to investigate the atmospheric responses to idealized diabatic heating.The results show that the two modes of heating forcing in the TP-IN region can affect the mid-latitude wave train and low-latitude circulation,finally affect the precipitation in CA and NC.The mid-latitude circulation responses to the two modes of the diabatic heating are approximately the same.The difference is that there is a cyclone over the west side of India,and an anticyclone over the east side.By calculating the wave activity flux from the simulation results,it can be obtained that the energy both propagate from northern Africa to the west,and there is energy convergence in CA and NC,leading to the strengthening of the trough in CA and NC.(4)Sea surface temperature is often an important factor that influences precipitation in India and the southeastern TP.The first mode is significantly related to the SST in the southeastern Indian Ocean and the Middle East Pacific Ocean,while the second mode is significantly related to the South Indian Ocean Dipole(SIOD)in the early spring,and the mechanism of how SST affect the TP-IN thermal mode needs further analysis.