How do lead-lag SST-rainfall relationships develop on intraseasonal time scale

The monthly mean simultaneous correlation between SST and rainfall shows negative correlation in the oceanic summer monsoon regions. To understand the origin of this negative correlation, we examine the lead-lag correlation of SST and Rainfall rate on intraseasonal time scales using TRMM data. Regions of robust SST-Rainfall (SST-R) coupling is defined by both the lead and lag correlation being statistical significant at the 95% confidence level. The region of robust coupling is strongly correlated with the intraseasonal variance of the precipitation rather than the intraseasonal variations of SST, suggesting that atmospheric ISO determines the robust SST-R coupling. Throughout the year, the robust coupling is strong over the warm pool region. In addition, the eastern North Pacific and western tropical Atlantic are also regions of robust coupling in boreal summer. The phase relationship between SST and precipitation in boreal summer differs from that in boreal winter and transition season. In the off equatorial region, the phase relationship between SST and rainfall is not in quadrature, which differs from that of the boreal winter MJO. It is suggested that this difference is attributed to the different roles that shortwave radiative flux plays in changing SST.