The 1930s drought event in the North American Great Plains region—The Dust Bowl—is one of the best-studied historical and climatological events in U.S. history. We present an analysis of a recently available daily climate data set for the conterminous United States during the 1930s focusing on changes in the occurrences of daily weather patterns in comparison with the longer-term averages. We look at changes in such things as return period of measurable rainfall, exceedance of different threshold values for maximum daily temperature and precipitation in the Dust Bowl region, wind patterns, and the cumulative impact of these climatic conditions on the regional landscape as recorded in aeolian depositional histories in the western Sandhills region of Nebraska. Preliminary results from a geomorphic study indicates local remobilization within the western Nebraska Sandhills of 1 to 4 meters of material significantly impacted the land surface cover, local drainage patterns, and human occupants. Application of this new daily climate data set in a dune mobilization model based on the balance precipitation and potential evapotranspiration will allow us to assess the plausibility of climate as the primary forcing of dune reactivation during the 1930s Dust Bowl.

Previous studies have noted that the Dust Bowl drought was characterized by three successive episodes of dryness and above average temperatures, interrupted by about a year or so (in 1932 and 1935) with normal or above precipitation. Studies of the relationship between climate and dune activity in three different climatic zones that are progressively more arid (a cross-section from the western Great Plains through the Chihuahuan desert in southern New Mexico and the Colorado Desert in southeastern California, indicate that aridity, as defined be the ratio of precipitation to potential evapotranspiration is the more critical parameter in comparison with wind strength.

We will evaluate the strength of the 1930s Great Plains drought by ranking different measures of drought during that time with the available historical record in the region. We will also compare the strength of 1930s drought with available paleoclimate records, such as tree-rings and geomorphic data. We will also consider the impact of future drought in the region in the context of present day land use practices and other changes in the landscape of the U.S. Great Plains.

References Diaz, H.F., 1983: Some aspects of major dry and wet periods in the contiguous United States, 1895–1981. J. Clim. Appl. Meteor., 22, 3–16. Muhs, F.R. and V.T. Holliday, 1995: Evidence of active dune sand on the Great Plains in the 19th century from accounts of the early explorers. Quat. Res., 43, 198–208. Skaggs, R.H., 1975: Drought in the United States, 1931–40. Ann. Assoc. Amer. Geogr., 65, 391–402. See also: http://geochange.er.usgs.gov/sw/impacts/geology/sand/