Utilizing identical climate indices as predictors for all climate divisions within large basins may result in unreliable rainfall forecasts at the subbasin scale. This study aimed to develop a new approach to identify the most effective predictors among large-scale climate indices for seasonal rainfall forecasting in small areas. The proposed approach combines a Selective Singular Value Decomposition method (SSVD) with a Non-linear Sequential Forward Selection method (NLSFS). Applying the new algorithm for seasonal rainfall forecasting within two climate divisions in Karkheh basin, Iran, indicated that the climate indices identified by the SSVD differed between the study areas. The combination of these indices exhibited approximately an 11% higher correlation with seasonal rainfall compared to those derived from the SVD method. Moreover, NLSFS significantly enhanced the forecast accuracy compared to the frequently employed linear Sequential Forward Selection (SFS) method, and the optimal predictors chosen by the two methods differed across all seasons.

Keywords