Current Trends in Land–Atmosphere Coupling Related to Drought

In a changing climate, the potential for increased frequency and duration of drought implies devastating impacts on many aspects of society. Recent summers in the United States have been plagued by intense droughts that have caused significant economic impact to society. In particular, the 2012 drought was termed by many as a “Flash drought”, due to its quick development and intensification. One possible mechanism for the sudden development of drought is through land-atmosphere interactions. In particular, during the convective season, when the potential of extreme drought is the highest, the soil moisture can provide a feedback mechanism that can cause or intensify drought. Recent work has developed a classification of land-atmosphere interactions that was the basis for a Coupling Drought Index (CDI) that assesses the impact of coupling on drought. In this work, data from satellite remote sensing and reanalysis is used to analyze the trend in CDI over the last 30 years. The results suggest that the Western U.S. has seen an increase in coupling drought conditions, while the Northern Great Lakes has seen a decrease in drought conditions. From a global perspective, South America, South and West Africa, Northern Australia and the Pacific Islands have seen a decrease in drought conditions, while parts of North Africa, the Middle East and Central Eurasia have seen an increase in drought conditions. The uncertainty, implications and limitations of this work are also discussed.