A case study of the extreme weather event in southern South America: The 2008 – 2009 drought.

ADRIANA E. FERNÁNDEZ; MARIO N. NUÑEZ; HECTOR CIAPPESONI; ALFREDO ROLLA

Foz do Iguassu, Brazil

Conferencia; The Meeting of the Americas; 2010

American Geophysical Union

Key words: extremes, drought, observation, analysis This paper presents an analysis of the 2008 – 2009 drought in the southern south region of South America. During 2008 and 2009 one of the worst droughts in 50 years devastated crops, dry rivers and springs, and killed cattle in Argentina, a phenomenon also impacted on socio-economic and productive communities and regions. La Niña 2008-2009 depleted water reserves not only in Argentina but also in Paraguay, Uruguay and Brazil. According to the Meteorological Weather Service of Argentina (SMN), during 2008 observed rainfall values were bellow normal in most of the humid and semi-humid region of the country (the Pampas), comparing with the main value of the period 1961-1990. The accumulated rainfall in the center of the region represented only 40-60% of the normal values, and in some locations values of precipitation were the lowest of the last 47 years. The Observed rainfall during 2009, in spite that rainfall during February, March and July exceed normal values in some locations of the region, still precipitation were bellow normal, considering the total rainfall for January-August 2009. Drought associated to La Niña event remained during most of year 2009. The South American low-level jet is a major source of moisture for northern and central Argentina. We have checked for trends in this source of moisture using the NNR, and found that except in high latitudes the flux of moisture is dominated by the mean flux term, and that the eddy fluxes are an order of magnitude smaller. An analysis of the mean flux for the period 1961 – 1990 and comparing whit the annual mean fluxes for the years 2008 and 2009, indicates a very clear decrease in moisture transport from the Amazon to northern and central Argentina, suggesting that this is a major cause of the observed drought during the years 2008 and 2009.