Estimating winter and spring rainfall in the Comahue region (Argentine) using statistical techniques

GONZÁLEZ, MARCELA HEBE; CARIAGA, MARÍA LAURA

Advances in Environmental Research. Volume 11

NOVA PUBLISHER

Lugar: NUEVA YORK; Año: 2011; p. 103 - 118

Most energy resources of Argentina come from hydroelectric stations operating in the Comahue region, like “El Chocon” and “Piedra del Aguila”. The Comahue region is located in the area of the Andes range, between 38ºS and 43ºS and two main basins are located there: the Limay River (LRB) and the Neuquen River (NRB) basins. The possibility to improve the accuracy of seasonal precipitation forecast, is the principal objective of this chapter. LRB and NRB mean rainfall series were built in order to investigate the association between them and SST and other circulation patterns in the previous month. A regression model was elaborated for MJJ rainfall in both basins. They reflect the importance of SST in tropical Indian Ocean, the wave train over the Pacific Ocean and the ENSO phase that are observed the month before (April), to predict MJJ rainfall.     The model for ASO rainfall forecast in LRB indicates that previous SST (July) doesn´t influence ASO rainfall as in the case of MJJ precipitation, but the geopotential height, related to the displacement of low pressure systems along the Pacific Ocean, plays a relevant role. This fact is indicative that the dynamical systems are the main factor that contributes to generate precipitation in the study area. Meanwhile, in the case of ASO NRB, SST is more relevant. Positive SST anomalies enhance the moisture in the atmosphere and both, moist air and deep cyclonic anomalies, reinforce the intensity of rainy systems that arrive to the Comahue region from the Pacific Ocean.  The application of Climate Prediction Tool from IRI, using canonical correlation analysis showed that correlation map between observed and forecast rainfall in MJJ is significant all over the area of study and it increases towards the west and the northwest. The analogous correlation map for ASO rainfall is not so good but it seems to be efficient in the NRB with correlation decreasing towards the southwest. The results let us conclude that there are factors of predictability for rainfall in both basins, and so, more investigations must be done in order to improve the forecast. This is a relevant aspect in order to better regulate the power production derived from hydro electric sources