The Impact of Tropical Indian Ocean Variability on Summer Surface Air Temperature in China

Evidence is presented that the boreal summer surface air temperature over south China and northeast China is remotely influenced by the Indian Ocean Basin mode (IOBM) sea surface temperature (SST) anomalies. Above-normal temperature in south China and below-normal temperature in northeast China correspond to a simultaneous Indian Ocean Basin warming. The teleconnection from Indian Ocean SST anomalies to China summer surface air temperature is investigated using observations and an atmospheric general circulation model (AGCM). The results herein indicate that the tropical Indian Ocean Basin warming can trigger a low-level anomalous anticyclone circulation in the subtropical northwest Pacific and an anomalous cyclone circulation in midlatitude East Asia through emanating a baroclinic Kelvin wave. In south China, the reduced rainfall and downward vertical motion associated with the anomalous low-level anticyclone circulation lead to above-normal summer surface air temperature. In northeast China, by contrast, upward vertical motion associated with the anomalous cyclone leads to below-normal summer surface air temperature.