Trends and Spatial Variability in Dry Spells across the South-Central United States

Abstract

nnual average and maximum spells with no precipitation in the southern United States are analyzed. In this study, dry spells are defined as consecutive days with no measurable rainfall. The study area includes 70 weather stations in Texas, Oklahoma, Louisiana, Arkansas, Mississippi, and Tennessee. Interarrival times between daily precipitation records for each station provide the data for this analysis. All 70 stations were analyzed from 1950 to 2013. Six stations that each have data for more than 100 years were analyzed for the period from 1908 to 2013. Approximately 25% of stations in the region show significant negative trends through time, indicating that dry spells have become shorter through time at these locations. The strongest geographical indicator for the number of consecutive dry days across this region was longitude. Dry spells tend to have had longer durations at the westernmost stations because of natural climatological controls.