Delayed Atmospheric Response to ENSO

In this paper the atmospheric response to the tropical Pacific sea surface temperature (SST) anomalies following the ENSO cycle is analyzed. This analysis differs from the traditional composite or regression analysis where the atmospheric response to simultaneous SST anomalies is documented. The present analysis, in principle, can capture atmospheric anomalies related to ENSO which may persist after the tropical Pacific SST state had weakened. From the analysis of observational data for the 1950-1996 period we show that for the summer following the peak of SST anomalies in the boreal winter, the atmospheric response persists well beyond what could be inferred from the analysis of simultaneous response to SST anomalies alone. This is particularly evident for the upper level atmospheric height anomalies in the tropical and sub-tropical latitudes. For example, the upper level heights continue to stay above normal, well after the tropical Pacific SST anomalies start to return to normal. Different possible causes for this delayed response to ENSO are also discussed