Relationships between convective activity in the Maritime Continent and precipitation anomalies in Southwest China during boreal summer

Abstract

Using the outgoing long-wave radiation (OLR) data from NOAA, the ERA-Interim reanalysis products from ECMWF, and daily observations at 756 stations provided by National Meteorological Information Center of China Meteorology Administration, we have examined the relationships of interannual variations of summer precipitation in Southwest China with the convective activity in the Maritime Continent (MC) region by employing the singular value decomposition (SVD) method and the regional climate model RegCM4.4. The first SVD mode (here after SVD1) indicates that high precipitation anomalies in Southwest China correspond to abnormally weak convective activity in northeastern MC and strong convective activity in Southwestern MC if the time-series of coefficients of SVD1 is in positive phase. When convective activity are anomalously strong in Southern MC, the anomalous divergence at 700 hPa and convergence at 200 hPa are observed over the tropical western Pacific and South China Sea. The propagation of wave energy at 700 hPa from Western Europe and the tropics provide a favorable condition for inducing more precipitation in most of Southwest China. The atmospheric water vapor transport from northern Indochina and the South China Sea to Southwest China intensifies while the western Pacific subtropical high is stronger than normal and extends more westward. All these results along with the simulations demonstrate that the summer precipitation in Southwest China is significantly affected by the convective activity over the MC region. These results above are helpful for our better understanding the role of the MC in regulating the summer climate in Southwest China.