Numerical Study of the 1988 Drought in the United States

Abstract

During the summer of 1988, a severe drought caused extensive loss of crops in the Midwest and Gulf States of the United States. The Purdue Regional Model (PRM), with comprehensive atmospheric physics and soil-vegetation surface package, has been integrated continuously for thirty days of June 1988 to study circulation and surface hydrology. The results show that the PRM is capable of reproducing the evolution of the observed weather and monthly mean fields of June 1988, when an extensive ridge located over the hot, dry North America suppressed the moisture supply from the oceans. Sensitivity test shows that under the observed SST and large-scale wave pattern, the model can generate more precipitation using wet soil as the initial condition, but a strong stationary anticyclone still exists in the US. The wet soil also enhances anticyclonic circulation centered over the Rocky Mountains, and the offshore flow in Texas and Gulf States, soil becomes dry eventually. Hence, the dry soil over the central US alone is insufficient to instigate the anomalous warm ridge, but could have had a role in its persistent drought due to the weakening of the low-level jet in Texas and Oklahoma region and less evaporation from the land surface.