United States Drought of 2007: Historical Perspectives

The impacts of the United States drought of 2007 to both society and ecosystems were substantive and included multi-billion dollar agricultural losses and the second worst wildfire season on record. The purpose of this paper is to place the 2007 drought in historical perspective relative to the climate record from 1895–2007 to increase our understanding of this hazard and contribute to improvements of drought mitigation plans. We compared the 2007 drought historically against the climatic record (1895–2007) using the Palmer Drought Severity Index (PDSI). We then examined the temporal progression of the 2007 drought and placed the peak month of drought severity (November) in historical perspective using rankings of severity and statistical recurrence intervals. Moreover, we examined the climatic factors (e.g. geopotential height anomalies) that contributed to both abnormally dry and wet conditions recorded within the continental United States. While there were regions that experienced the worst drought on record both annually and in November during the calendar year 2007, this year was not as severe as other notable drought years. November 2007 ties (with 5 other years) for the 12th worst on record in terms of the number of climatic divisions experiencing the worst November drought. Statistically, drought/wetness conditions in November 2007 were not exceptionally extreme, with almost all of the calculated statistical recurrence intervals being much less than the 113 year period of record