DYNAMICS OF STATIONARY WAVE ANOMALIES DURING THE 1986 87 EL-NINO/

The dynamics of the wintertime atmospheric response to the 1986/87 El Nino SST anomalies is studied. A GCM used for this purpose simulates a wave train over the Pacific/North American (PNA) region that agrees c losely in amplitude with that observed, but phase shifted 30-degrees t o the east. Linear baroclinic model experiments are performed in order to determine the origin of the GCM and observed stationary wave anoma lies, with particular focus on the cause for GCM failure. Diagnostics with the linear model reveal that the GCM and observed wave train anom alies are maintained by very different processes. In the GCM, the forc ing due to tropical diabatic heating and transient vorticity fluxes ar e equally important over the PNA region. In the observations, the tran sient vorticity fluxes assume the primary role. The cause for these di screpancies is traced to the different dynamic influences of suppresse d rainfall near Indonesia. The associated diabatic cooling is found to excite a large amplitude wave train over the PNA region in the GCM, w hile no significant extratropical response to cooling is found in the observations. The combined effects of the diabatic cooling and the reo rganization of the storm track transients by the remotely forced wave train acts to shift the GCM's wave train well to the east of that obse rved. Due to uncertainties in the observed diabatic forcing, however, it is not clear to what extent the GCM's failure is due to errors in t he simulated anomalous forcing and/or to the GCM's mean climate error.