Responses of East Asian winter and summer monsoons to autumn sea surface temperature anomalies in tropical Indian Ocean

The relationships between autumn sea surface temperature(SST) anomalies in the tropical Indian Ocean and the strength of the East Asian winter and summer monsoons are investigated by analyzing Reynolds monthly SST dataset and NCEP/NCAR atmospheric reanalysis data.The results show that there are two dominant modes of autumn SST anomalies in the tropical Indian Ocean,the unanimous signed basin-wide(USB) mode and the Indian Ocean dipole(IOD) mode,respectively.The USB mode mainly shows a long term warming tendency of the tropical Indian Ocean,while the IOD mode reveals the interannual variations.By removal of ENSO-dependent variability,the SST anomalies in the tropical Indian Ocean mainly appear to be the USB and IOD modes.The USB mode exhibits significant negative correlations with the strength of the East Asian winter monsoon and the East Asian subtropical summer monsoon.When the positive(negative) IOD exists in the tropical Indian Ocean during the preceding boreal fall season,the South China Sea summer monsoon is weakened(strengthened),and the East Asian subtropical summer monsoon is strengthened(weakened).The relations of the dominant modes to the strength of the East Asian winter and summer monsoons are ENSO-independent variable,but the significance of the correlation can be modulated by ENSO.