The 1998 Oklahoma-Texas drought: mechanistic experiments with NCEP global and regional models

Song-You Hong
Department of Atmospheric Sciences, Yonsei University, Seoul, Korea

Eugenia Kalnay
Department of Meteorology, University of Maryland

Abstract: The Oklahoma/Texas (OK/TX) drought of the 1998 summer was strong and persistent, with soil moisture reaching levels comparable to the 1930's Dust Bowl. For the record strong 1997-98 El Niņo, the seasonal operational predictions were skillful over much of the Unites States, but the OK/TX drought was not predicted. Here we present results from mechanistic experiments to clarify the origin and maintenance of this extratropical climate extreme. In addition to using global atmospheric models, we used a regional model to isolate regional climate feedbacks. We conclude that during April and May 1998, SST anomalies together with a favorable atmospheric circulation helped establish the drought. During June through August, the regional positive feedback associated with lower evaporation/lower precipitation contributed substantially to the maintenance of the drought. The drought ended in the fall with weaker heating and stronger synoptic waves.