عنوان مقاله [English]
Principal components and cluster analysis were used for grouping the monthly precipitation over Iran into some homogeneous regions. Such grouping is considered as an essential and primary step for pre-process in downscaling of the general circulation models outputs. The monthly precipitation data of 42 stations for the period of 1967-2003 (37 years) forming a 42×444 matrix was used as input file of the principal components analysis. Using PCA, this matrix was reduced into a 42×33 matrix that accounted for about 96% of total variance in the observational time series. The reduced matrix was used as the input file of the Cluster analysis. The results regionalized the country into six different regions.