Flash droughts in southern South America as captured by ERA5 reanalysis data

LOVINO, MIGUEL A.; BERBERY, ERNESTO HUGO; MÜLLER, GABRIELA VIVIANA; PIERRESTEGUI, MARÍA JOSEFINA

Conferencia; EGU General Assembly 2021; 2021

This study investigates the frequency of occurrence of two types of flash droughts in southernSouth America: heatwave flash droughts (HWFD) and precipitation deficit flash droughts (PDFD).To this end, we employ ERA5 products at 0.25° horizontal resolution under the assumption thatthey add valuable information in regions of scarce observations. The analysis is based on1979-2019 ERA5 pentad data of precipitation (P), 2-m air mean temperature (T),evapotranspiration (ET), and root-zone soil moisture (SM). HWFD and PDFD exhibit differentfunctional mechanisms related to surface moisture and surface energy fluxes. In HWFD, high Tcauses ET to increase and lead to decreases of SM. When combined with negative P anomaliesbefore a drought´s onset, there is a significant increase in the magnitude of negative SManomalies. The mechanism of PDFD formation starts with a precipitation deficit prior to thedrought onset. The lack of precipitation causes a reduction in SM and ET, which results inincreased T (the Bowen ratio and T increase in response to the decreased ET).