Flash drought climatology over the Argentine humid Pampas

Abstract

Drought is one of the meteorological events whose onset is generally slow and mainly related to a precipitation deficit. However, there are drought events that, unlike ordinary droughts, intensify in periods of less than one month, where the precipitation deficit is combined with high temperatures, higher wind intensity and/or lower atmospheric humidity, which generates a rapid decrease in soil moisture due to a substantial increase in evapotranspiration. These events are called Flash Droughts (FD). This study performs the first FD climatology over the Humid Pampas using ERA-5 Land soil moisture simulations at 14 meteorological stations in the region. The occurrence and main characteristics of these events were analysed using an FD index that considers both their intensification and severity. During the period 1981-2020, these events generally occurred during the November-May period, favoured by the seasonal increase in evapotranspiration. The duration of each SRD after the intensification period varied widely, lasting from a few weeks to several months, with a longer duration in seasons with fewer events. The FD represent a significant proportion of the total number of drought events, generally more than 40 % of the total number of ordinary drought events. Likewise, a significant increase in the frequency of FD was observed in the period 2001-2020 compared to the period 1981-2000. The 2017-2018 drought, that affected the Humid Pampa, was identified as a FD. This event was the most severe FD recorded between 1981-2020 period across 7 out of 14 stations resulting in significant economic losses as it coincided with the critical period for corn.