Evaluation of multiple reanalyses in reproducing temperature and precipitation indices over southern South America

BALMACEDA HUARTE, ROCIO; OLMO, MATIAS EZEQUIEL; POGGI, MARIA MERCEDES; BETTOLLI MARIA LAURA

Simposio; Joint WCRP-WWRP Symposium on Data Assimilation and Reanalysis; 2021

WCRP

Several temperature and precipitation indices, with special focus on extremes, were analysed in different sub-regions of southern South America (SSA) during 1979-2017 using multiple reanalyses, the CPC gridded dataset and the most extended network of meteorological stationsemployed in regional climate studies up to date. Reanalyses generally well represented the spatial patterns of the indices, although they showed some differences in extreme indices over large portions of SSA and tended to overestimate precipitation maximums, especially in southern Chile. Furthermore, ERA-Interim presented clear difficulties in reproducing precipitation near the Andes mountains, exhibiting the largest overestimations. This seemed to be improved in ERA5. When evaluating the long-term changes, most of the datasets agreed in general warming conditions, stronger and more homogeneous for the maximum temperature. NCEP1 and NCEP2 showed contrary temporal changes in almost all the temperature indices. Precipitation indices exhibited less consistent changes among reanalyses, notwithstanding, most of the datasets agreed in drier conditions in the arid region of Argentina as reflected by significant positive trends for dry spells and negative trends for the total annual precipitation. In terms of the inter-annual correspondence, reanalyses presented good correlations to the stations reference in the regional series. The use of reanalyses data to perform regional climate studies should consider the existent differences among them. Using multiple sources of information is strongly recommended to account for observational uncertainty, especially in regions like SSA, where data availability and its resolution are often limited.