Hotspots for flash drought occurrence in South America

LOVINO, MIGUEL; BERBERY, ERNESTO; MÜLLER, OMAR ; PIERRESTEGUI, MARÍA JOSEFINA; MÜLLER, GABRIELA

Congreso; 13th International Conference on Southern Hemisphere Meteorology and Oceanography (ICSHMO); 2022

American Meteorological Society

Flash droughts (FD), characterized by rapid soil drying, can negatively impact livestockand crop yields. We propose a novel FD definition based on root-zone soil moisture (SM)and soil hydraulic properties. The index is tested over South America to identify regionsprone to FD. We employ ERA5 1-m root-zone SM pentad data for the 1950-2020 periodcomplemented with the ERA5 field capacity and wilting point volumetric soil moisturevalues. We define an FD when the Soil Water Deficit Index (SWDI) decays from -3 to -5in 4 pentads. We also require that the SM depletion lasts at least 3 pentads to excludethose short events that deplete SM rapidly down but then recover up suddenly. We detectFD hotspots by counting the total number of FD events during the whole year over the1950?2020 period. To determine the spatial pattern of changes in FD occurrence, weestimate linear trends in time series of the number of FD events per year. We apply theMann?Kendall test to detect significant trends at the 5% significance level.We find that several regions in South America that are most beneficial for agriculture arealso the hotspots for FD occurrence, including croplands and grasslands over thePampas region in southeastern South America, northern Colombia, and northernVenezuela ? central Colombia. FD increased in most of South America between 1950and 2020. The most significant upward trends occurred in parts of the hotspots for FDoccurrence, namely southern Brazil, northern Colombia, and northern Venezuela