A COMPLEMENTARY DEPICTION OF THE INTERANNUAL VARIATION OF ATMOSPHERICCIRCULATION ASSOCIATED WITH ENSO EVENTS

A Simple diagnostic scheme, which combines a low-pass temporal filter (with an 18-month cutoff time) with a regular empirical orthogonal fun ction (EOF) analysis, is used to delineate the synchronous evolution o f El Nino-Southern Oscillation-related (ENSO-related) modes in various variables of the ocean-atmosphere system, Based on the causal relatio n chain of diabatic heating, divergent circulation and rotational flow , the diagnostic scheme extracts ENSO modes from the following data so urces: the Pacific sea surface temperature (SST), the past 14-years (1 979-1992) of data generated by the Global Data Assimilation System of the National Meteorological Center, and a 10-year (1979-1988) general circulation model climate simulation made at the Goddard Laboratory fo r Atmospheres. The analysis reveals the following: (a) the eigencoeffi cient time series of the first eigenmodes of selected filtered variabl es, which explain about 40-50% of their total variance, synchronize wi th the filtered SST averaged over Area NINO-3; (b) the spatial structu res of the first eigenmodes resemble the ensemble departures associate d with ENSO events of these variables from their long term means; and (c) the results show that the proposed scheme can be easily applied to isolate and illustrate the lime evolution of ENSO modes which exist i n the long term observational database as well as in climate simulatio ns.