Twentieth-century summer precipitation in South Eastern South America: comparison of gridded and station data

Abstract

South Eastern South America (SESA) has experienced one of the largest regional wetting trends in the world according to gridded datasets that cover the 20th century, such as Global Precipitation Climatology Centre monthly precipitation dataset in its version 4 (GPCCv4). The trend is strongest in the warm season and covers central and northern Argentina, Uruguay, Paraguay and Southern Brazil. This article examines the consistency of the trend and variability in the gridded product with that of local experience as recorded in station data. This is relevant to the use of both types of datasets for long-term climate studies, since the region has a limited amount of available station data with records extending back to the first part of the century. Both the station and gridded datasets show good agreement on the temporal variability of summer precipitation and its spatial patterns for different timescales. The magnitude of the wetting trend in SESA observed for December, January and February in GPCCv4 during the 1901–2000 period is more than 10 mm in the season per decade and is highly consistent with the trend observed in the station-based SESA average. The percentages of variance explained by the trend, decadal and interannual timescales are also assessed for both GPCCv4 and station data. The variance of the SESA precipitation contained at the decadal timescale matches well to the station-based and the GPCCv4-based indexes, but the latter suggests a larger fraction of variance attributable to the trend and a lower fraction explained by interannual scales, as compared to the station-based index. For all the timescales analysed, there is a good agreement in the spatial patterns observed for GPCCv4 and those suggested by the available station data.