Extreme precipitation records in Antarctica

Abstract

Monitoring extreme precipitation records (EPRs), that is, the most extreme precipitation events, is a challenge in Antarctica due to the reduced number of stations available in the continent and the limitations of the instrumentation for measuring solid precipitation. Still, extreme precipitation events may contribute substantially to the variability of ice sheet snow accumulation and even may cause important ecological impacts. This article presents the Antarctic EPRs at different temporal scales, studying the relationship between precipitation amount and temporal duration through a power scaling law, ranging from 1 day to 2 years. This is achieved using precipitation datasets from the ERA5 reanalysis and the RACMO2 regional climate model. Moreover, we present a selection of EPRs case studies examining the synoptic mechanisms that produce such events in Antarctica. Despite ERA5 EPRs are usually lower than those found in RACMO2, they present similar scaling exponents. EPRs are found in Loubet and south Graham Coasts, in the central section of the Antarctic Peninsula, and in the north of Alexander Island, where orographic enhancement increases precipitation amounts. As expected, Antarctic EPRs are much lower than world-wide EPRs, ranging from 6 to 10% at short temporal scales (from 1 to 10 days) and from 10 to 20% at long temporal scales (from 90 days to 2 years) in ERA5. Regional variability of extreme precipitation scaling exponents show similar spatial patterns than previously calculated precipitation concentration. On the other hand, the lack of summer events in Antarctic EPRs evidences that stronger fluxes in winter play a key role on extreme precipitation during EPR events, which are mainly produced by long-range transport of moisture by atmospheric rivers impinging on Antarctic mountains.