Extraordinary heat during the 1930s US Dust Bowl and associated large-scale conditions
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Unusually hot summer conditions occurred during the 1930s over the central United States and undoubtedly contributed to the severity of the Dust Bowl drought. We investigate local and large-scale conditions in association with the extraordinary heat and drought events, making use of novel datasets of observed climate extremes and climate reanalysis covering the past century. We show that the unprecedented summer heat during the Dust Bowl years was likely exacerbated by land-surface feedbacks associated with springtime precipitation deficits. The reanalysis results indicate that these deficits were associated with the coincidence of anomalously warm North Atlantic and Northeast Pacific surface waters and a shift in atmospheric pressure patterns leading to reduced flow of moist air into the central US. Thus, the combination of springtime ocean temperatures and atmospheric flow anomalies, leading to reduced precipitation, also holds potential for enhanced predictability of summer heat events. The results suggest that hot drought, more severe than experienced during the most recent 2011 and 2012 heat waves, is to be expected when ocean temperature anomalies like those observed in the 1930s occur in a world that has seen significant mean warming.
KeywordsExtreme heat Drought Seasonal predictability Climate variability Teleconnections 20th century reanalysis GHCNDEX
This study was supported by the Australian Research Council grants CE110001028, LP100200690 and DE150100456, the U.S. National Science Foundation Grant AGS1243125 (JTO), and a Victorian Centre for Climate Change Adaptation Research Fellowship (JTO). We are grateful to Gil Compo for providing daily data from all 20CR ensemble members to calculate the extremes indices. Support for the 20CR Project is provided by the U.S. Department of Energy, Office of Science Innovative and Novel Computational Impact on Theory and Experiment (DOE INCITE) program, and Office of Biological and Environmental Research (BER), and by the National Oceanic and Atmospheric Administration Climate Program Office. We also express our thanks to two anonymous reviewers for their constructive comments that helped to improve the manuscript.
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