DEPENDENCE OF THE SURFACE DAILY EXTREME TEMPERATURES IN LA PLATA BASIN ON THE DAILY CIRCULATION FEATURES IN SOUTHERN SOUTH AMERICA AND ITS FUTURE PROJECTION

9. BETTOLLI ML; PENALBA OC; KRIEGER, PA

Nouméa

Conferencia; 10th International Conference on Southern Hemisphere Meteorology and Oceanography; 2012

Daily extreme temperatures are key variables in climate change studies, due to their impact on human activities. La Plata Basin is one of the most important agriculture and hydropower producing regions worldwide, where extreme climate events have a significant socio-economic impact. The aim of this work is to analyze the dependence of the maximum and minimum temperatures in the south of La Plata Basin region on the large-scale circulation in Southern South America and its future projection. Daily mean sea level pressure (SLP) fields from NCEP reanalysis 2 were used to represent observed circulation for the period 1979-1999. The analyzed seasons were austral summer and winter for the spatial domain from 15oS to 60oS and from 42.5oW to 90oW. The circulation types were obtained by combining the Principal Component Analysis with the k-means Cluster Analysis. Daily maximum and minimum temperatures were used from the gridded datasets of the Claris LPB Project (?A Europe-South America Network for Climate Change Assessment and Impact Studies in La Plata Basin?). Global Circulation Models SLP daily fields were used to describe present and future low level circulation. The outputs were obtained from the WCRP CMIP3 and CMIP5. The study of the temperatures conditioned by the observed surface circulation was done through a test for the comparison of mean values and a non-parametric test for the comparison of distributions of maximum and minimum temperatures associated with each circulation pattern. The results indicate that specific daily circulation patterns can be identified as responsible for a significant contribution to the extreme temperature anomalies. The models are able to reproduce the full range of summer and winter circulation types found in the NCEP climatology. Future projections indicate a change in the frequency of some patterns for future climate, which would have implications on the distribution of daily extreme temperatures.