the application of ann for downscaling gcms outputs for prediction of precipitation in across southern iran

in this study, the artificial neural networks (anns) and regression models were used to downscale the simulated outputs of the general circulation models (gcms). the simulated precipitation for 25.18 º n to 34.51 º n and 45 º e to 60 º e, geopotential height at 850 mb and zonal wind at 200 mb for 12.56° n to 43.25° n and 19.68° e to 61.87° e data sets as the predictors were extracted from echam5 gcm for the period 1960-2005. the observed monthly precipitation data of abadan, abadeh, ahwaz, bandar abbas, bushehr, shiraz and fasa stations as the predictand were extracted for the period 1960-2005. the principal components (pcs) of the simulated data sets were extracted and then six pcs were considered as the input file of the ann and multiple regression models. also the combinations of the simulated data sets were used as the input file of these models. the periods 1960-2000 and 2001-2005 were considered as the train and test data in the ann, respectively. the pearson correlation coefficient and normalized root mean square error results indicated that ann predicts precipitation more accurate than multiple regression. for the monthly time scale, the geopotential height is the best predictor and for the seasonal time scale (winter) the simulated precipitation is the best predictor in ann based standardized precipitation principal components.