Extreme Wet and Dry Events over Southeast Brazil and Associated Atmospheric Circulation Patterns

In the last decades, extreme precipitation events have caused significant social and economic impacts in the Southeast Brazil, the country's most economically developed region with the highest population concentration. Currently this area is suffering the effects of a prolonged period of summer rainfall deficits initiated in 2012, which negatively impacted its energy production and agriculture and caused severe reduction in the population's water supply. This research will examine the atmospheric circulation features related to rainfall variability over Southeast Brazil with emphasis on periods of extreme dry and wet conditions. The analysis is carried out using: (1) gridded daily precipitation analyses from the NOAA Climate Prediction Center (CPC) for the 1948-2005 period (Cressman method) and for the 1979-2015 period (Optimum Interpolation method), (2) IR cloud brightness temperatures (1980-2009) from the National Climatic Data Center (NCDC) and (3) gridded circulation fields from the NCEP/NCAR Reanalysis (R1) and the Climate Forecast System Reanalysis (CFSR) available from CPC. The daily rainfall analyses are used to document interannual to decadal variability of the seasonal total rainfall. Such observations indicate that 2013/2014 and 2014/2015 rainy seasons (September-May) in Southeast Brazil were the driest since the mid-1950s. Aspects of the daily extremes examined include their historical ranking, possible ENSO relationship and recent trends. Datasets (2) and (3) are used to construct composites of extreme rainfall events to determine their related atmospheric circulation patterns and the variability of the South American Monsoon System (SAMS).