Prevailing anomaly patterns of the Global Sea Surface temperatures and tropospheric responses

Abstract

A synoptic classification of observed anomaly fields of the monthly global sea surface temperatures (SSTs) is presented for the period of 1955-1993. The monthly anomaly fields are grouped into characteristic seven types. The Northern Hemisphere tropospheric responses to these SST types are described in terms of the geopotential height (Z) fields at 700, 500, and 300 mb and thickness fields for 700-500 mb and 500-300 mb. Each type of SST anomalies is associated with a distinct anomaly field of Z, whose characteristic patterns are consistent from the lower to upper troposphere. The climatic variations during the past four decades are depicted by the prevailing monthly SST patterns. The dominance of the El Nino - Southern Oscillation (ENSO) type anomaly fields during the recent years characterizes the climatic mode prevalent at present. Principal components of the SST anomaly fields during the period of July 1991 to December 1993 are presented for the description of the recent ENSO type SST patterns A possible utilization of defined El Nino Index (ENI) in the long-range projection of the atmospheric circulation is examined with cross-correlation between the preceding ENIs and following tropospheric circulation. The usefulness of ENIs as a predictor is indicated at the seasonal range.