THE EFFECT OF SST AND SOIL-MOISTURE ANOMALIES ON GLA MODEL SIMULATIONS OF THE 1988 UNITED-STATES SUMMER DROUGHT

A series of simulations of the late spring and early summer of 1988 we re conducted in order to study the relative importance of different bo undary forcings to the Goddard Laboratory for Atmospheres model's simu lation of the heat wave and drought over the Great Plains of the Unite d States during this time period, Separate 60-day simulations were gen erated from 10, 20, and 30 May 1988 with a variety of boundary conditi on datasets. For the control experiment, climatological boundary condi tions were used. This was followed by experiments in which either the observed 1988 sea surface temperatures (SST) or derived 1988 soil mois ture values, or both, were used in place of the climatological fields. Additional experiments were conducted in which only tropical or midla titude SST anomalies were used. The impact of the different boundary f orcings was evaluated relative to the control simulations of the preci pitation and surface air temperature over the Great Plains. It was fou nd that the tropical SST anomalies had a significant effect in reducin g precipitation in this area, while the midlatitude anomalies did not. Due to the prescribed climatological soil moistures for the SST exper iments, a significant increase in surface temperature did not occur in these simulations. In contrast, the simulations with the anomalous 19 88 soil moistures produced both a larger reduction of precipitation an d a significant increase in surface temperature over the Great Plains. The simulations with both anomalous SST and soil moisture showed only a slight augmentation of the heat wave and drought relative to the ex periments with anomalous soil moisture alone.