Trends in the drought affected area in Southern South America

OLGA PENALBA; JUAN ANTONIO RIVERA

Nouméa

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

American Meteorological Society (AMS) and Institut de recherche pour le développement (IRD)

Under current global climate changes, it is necessary to analyze the spatial and temporal variabilities of drought events, in order to improve the water resources management and mitigate their impacts. Drought conditions were identified by the Standardized Precipitation Index (SPI). We analyzed the evolution of the percentage of locations with moderate drought months (months with SPI = -1) in Southern South America during 1961-2008. We used precipitation data from 55 meteorological stations belonging to Argentina, Brazil and Paraguay, whose spatial distribution was homogeneous in order to obtain a representative percentage of drought affected area. The SPI was computed for time scales of 1, 3, 6, 9 and 12 months, which allowed monitoring of different types of drought –meteorological, agricultural and hydrological-. The percentage of stations with drought tends to decrease approximately 3% per decade, considering deficits of 12 months, while this decrease is in order of 1% per decade on a scale of 3 months. This fact indicates that as the time scale increase, the area affected by drought decreases further. On a 12 month time scale, the droughts of 1962 and 1988-1989 affected more than 60% of the stations; while on the time scale of 6 months, this occurred during the droughts of 1962, 1968 and 1971. The increase in the drought affected area since 2000 in all time scales is remarkable, reaching a 40% of surface during 2008. The interannual variability in the time series showed significant cycles from 3 to 9 years, corresponding to El Niño-Southern Oscillation timescales. The largest spatial extents of droughts were recorded during La Niña events.