FLASH DROUGHT SPATIOTEMPORAL VARIABILITY IN THE CONTINENTAL UNITED STATES AND ITS PREDICTION FROM ATLANTIC AND PACIFIC SEA SURFACE TEMPERATURES

Flash droughts are extreme climate phenomena that occur at the subseasonal-to-seasonal (S2S) timescale and develop with rapid onset and intensity. While flash droughts have significant socio-environmental impacts, its spatial and temporal variability and potential predictability from sea surface temperatures (SST) are still not well understood. The overall goal of this research is to assess the spatial and temporal variability of flash droughts in the continental United States (CONUS) and its predictability from SST in the Atlantic and Pacific oceans. The flash drought events are characterized using the evaporative demand drought index (EDDI) at the weekly timescale between September 1981 and December 2018. A hierarchical agglomerative clustering algorithm identifies geographic clusters where flash drought events occur synchronously over time. We identify the optimal number of clusters and further analyze the distribution and severity of flash drought occurrences within each cluster to understand the spatiotemporal variability of flash drought events. A spectral analysis on seasonal mean EDDI values is conducted to determine cycles and trends of flash drought events for each cluster. We then explore associations between SST anomalies in the Pacific and Atlantic oceans and flash drought events, and further evaluate flash drought predictions using the identified SST patterns. The results reveal the spatial and temporal variability of flash droughts in CONUS and its influential SST patterns from Atlantic and Pacific oceans. Such understanding will improve the current S2S prediction and management of flash droughts in the United States.