Linkages Between Heatwave Conditions and Flash Drought: A 2012 Great Plains Case Study

Abstract:

The relationships between heatwaves and drought events have been investigated extensively in the scientific literature, but specific studies examining the interactions between heatwaves and flash droughts are limited. Flash drought is characterized by the rapid intensification of drought conditions, which can result in large agricultural yield loss, impact the availability of short-term water resources, and lead to significant socioeconomic impacts. Similar atmospheric conditions (e.g., lack of precipitation, above-normal surface temperatures, less cloud coverage, etc.) can drive both flash droughts and the onset of heatwaves. Improved understanding of the links between heatwaves and flash drought could increase the predictability of such events. This improved predictability is necessary because it could help mitigate large agricultural loss, minimize human mortality, and improve subseasonal-to-seasonal prediction. In May 2012, drought conditions were ongoing across much of the southern plains and southwestern United States. Throughout the warm season, drought conditions propagated into the Midwest and intensified rapidly. In addition to the flash drought, anomalously high surface temperatures dominated the Central United States from spring through fall suggesting that these two features were related. This research uses the North American Regional Reanalysis (NARR) and two classifications for heatwaves to determine the onset and development of heatwave conditions across the Central United States (107°W -87°W) during 2012. One classification framework uses extremes in daily maximum and minimum temperature, whereas the other framework incorporates extremes in heat index; both approaches were performed using 3-hourly data. Extremes were defined as at or above the 95th percentile, and these extremes lasted for a minimum of 3 consecutive days to be classified as a heatwave. We highlight the similarities and differences in timing, intensity, and spatial extent of the cataloged heatwave(s) and of the flash drought across the Central United States during the May-October 2012 flash drought period. We hypothesize that the intensity and spatial extent of the defined heatwave(s), during the growing season of 2012, to be highly correlated to the flash drought with a positive feedback.