Effects of Soil Moisture on the Longitudinal Dryline Position in the Southern Great Plains

Abstract

AbstractThe dryline is among the most important meteorological phenomena in the Great Plains because of its significance in tornadogenesis, severe weather, and consistent rainfall. Past research has extensively examined the dynamics of the dryline; however, recent meteorological research looks beyond dynamics and focuses on land?atmosphere interactions. This study focuses on how soil moisture, a surrogate for evapotranspiration, affects the climatological longitudinal positioning of the dryline, presenting a climatological study for the months of April?June during 2006?15 in the southern Great Plains. Here, drylines are defined as specific humidity gradients exceeding 3 g kg?1 (100 km)?1 that do not deviate more than 30° from a north?south orientation; they were found to occur on 33.4% of spring days, and the most favorable position was ?100.9° at 0000 UTC. Specific humidity gradients ranged from 3.0 to 15.2 g kg?1 (100 km)?1, with an average value of 6.8 g kg?1 (100 km)?1. A relationship between the dryline longitudinal position and soil moisture was found; as soil moisture values increased, the dryline was located farther west, which suggests soil moisture may influence the longitudinal positioning of the dryline. There was also a relationship between the gradient of soil moisture and the intensity (specific humidity gradient) of the dryline, such that when longitudinal soil moisture gradients were strong (increasing from west to east), the dryline intensity increased.