Daily extreme rainfall events over South America as represented by four regional models and a new observational database

ARMELLE RECA REMEDIO; FEDERICO ARIEL ROBLEDO; ANNA SÖRENSSON; DANIELA JACOB; LAURENT LI; CLAUDIO MENENDEZ; OLGA PENALBA; ENRIQUE SANCHEZ; PATRICK SAMUELSSON; HERVE LE TREUT

Vienna

Conferencia; EGU General Assembly 2010; 2010

European Geophisical Union

The impact of climate variability on the environment and the economic activities mainly depends on changes in the frequency of occurrence of extreme events. Relatively few studies on regional variability of climatic extremes are found in the literature compared to the number of studies on climatic means. Relatively small changes in the mean could produce substantial changes in the frequency of extreme events. The objective of these work is to investigate the daily extreme rainfall events over South America as represented by four regional models and a newobservational database. Within the framework of the EU FP6 project CLARIS, four regional modelling groups have coordinated simulations of South American present climate (1992-2000). The models? domains cover the entire continent and are driven at the lateral boundaries by ERA40 reanalysis with a horizontal resolution of 50 km. Daily rainfall data used in this study were provided by different national institutions in Argentina, Uruguay, Brazil, Bolivia and Paraguay. The distribution of gauges is relatively homogeneous, except in certain areas in western Argentina and some areas of Brazil and Uruguay.Data quality assessment is an important requirement for climate research, particularly in the case of extreme rainfall. Considering the discontinuous nature of daily rainfall, the occurrence of intense rain may be considered erroneous without careful observation. The observation data are distributed across the La Plata Basin and southern South America regions (70W-40W and 40S-15S).We define a rain day as one on which the rainfall is greater than 0.1 mm and extreme rainfall event is considered when the daily rainfall is greater than the 75th, 90th and 95th daily percentiles threshold. For each subregion selected, the different daily percentiles are calculated for each meteorological station and for each grid point for each model. Both annual and seasonal results are presented.Due to the nature of climate model, representing the rainfall of an area determined by the model resolution (in this case 50x50km), we expect the percentiles of the station data to be higher than the results of the four models.However, the idea behind this comparison is to verify if the models can capture qualitatively the differences between different regions surrounding the La Plata Basin. In future studies, the results presented here will be compared with results from updated model versions driven by ERA-INTERIM.