Wind trends analysis in southern South America from weather station and reanalysis data

Abstract

Surface and upper-level wind speed changes were analysed for several weather stations distributed throughout Argentina from 1990 to 2020. Both annual and seasonal wind speed trends were estimated for individual surface stations and available rawinsonde data. In order to explore the nature of these changes, different percentile time series were evaluated. NCEP/NCAR and ERA5 data were also assessed to verify how these long-term changes are represented by the different reanalysis time series. A significant decline in measured surface wind speed is observed for most stations, with a reduction up to 13%·decade−1 in some of them. Despite differences on each station's wind speed distributions due to regional characteristics, the estimated trends were mostly negative for the annual 75th and 95th percentile time series. Upper-level stations registered positive trends especially in the upper troposphere (200 hPa) in northern Argentina, while Patagonia's wind profile showed significant positive wind speed trends at most levels. Reanalysis data have severe limitations to reproduce the observed behaviour in the near-surface levels, but managed to generate adequate estimates for the medium to high troposphere.