The Influence Of Apparent Heat Source Configuration Over The Tibetan Plateau On The Interannual Variability Of Precipitation Intensity In Southwest China During The Rainy Season

The socio-economic development is restricted by frequent drought and flood disasters in Southwest China due to the distinct wet and dry seasons.Investigating the mechanism of the influence of apparent heat source configuration over the Tibetan Plateau on the interannual variability of precipitation intensity in the Southwest China during the rainy season is significant for predicting the rainfall intensity,drought and flood disasters.In the study,precipitation data from 264 stations and JRA-55 reanalysis data were collected from 1979 to 2019 in the Southwest China.Then,the influence of configuration of apparent heat source over the Tibetan Plateau on the interannual variability of precipitation intensity in Southwest China during the rainy season was investigated using statistical method and numerical simulation.The main findings are as follows:(1)The first empirical orthogonal function of precipitation intensity in the rainy season is negative in northwest and east Sichuan,and positive in the rest parts of Southwest China.The second empirical orthogonal function manifests as a northeast–southwest seesaw pattern.Their time series are mainly featured by interannual variability.The regional precipitation intensity index can comprehensively reflect the temporal and spatial distribution of precipitation intensity in Southwest China during the rainy season.(2)The apparent heat source configuration over the north and south flanks of the Tibetan Plateau has a significant effect on the precipitation intensity of the Southwest China in the rainy season.Two key areas are located at area A(80.0°–97.5°E,35.0°–42.5°N)on the north Tibetan Plateau(NTP)and the area B(80.0°–97.5°E,23.75°–31.25°N)on the south Tibetan Plateau(STP),respectively.When the apparent heat sources are in negative phase at the NTP and positive phase at STP,northeasterly anomalous winds will excited in the Southwest China,and southwesterly anomalous winds in the eastern Bay of Bengal.These anomalous winds result in stronger precipitation intensity in the rainy season of Southwest China via enhancing water vapor convergence in the Southwest China.On the contrary,when the apparent heat sources are in positive phase at the NTP and negative phase at STP,the opposite condition happens.The apparent heat source configuration anomlies,established before the rainy season over the NTP and STP,could be used to predict the precipitation intensity of the Southwest China in the rainy season.(3)Simulation results of Linear Baroclinic Model and Gerernal Atmopshric Circulation Model confirm the key physical process revealed in the observational anylasis.When the apparent heat source anomalies are individually imposed on NTP or STP,the simulation results are different from the results of observation analysis to a larger degree.When the apparent heat source anomalies are imposed on the NTP and STP,the simulation results are similar to the results of observation analysis.The synergistic effect of the apparent heat source configuration over the NTP and STP play the most important role in the interannual variability of precipitation intensity of the Southwest China in the rainy season.