Spatial variability analysis of precipitation and its concentration in Chaharmahal and Bakhtiari province, Iran

The spatial variability of annual precipitation and precipitation concentration has been analyzed in Chaharmahal and Bakhtiari province using data from 42 stations between 1981 and 2012. For this purpose, the correlation decay distance (CDD) and the coefficient of variation of annual precipitation have been computed at each station to show the inter-annual variability of precipitation. Results showed an increasing gradient from the southwest to the northeast in inter-annual precipitation variability. The degree of seasonality of precipitation and the year-to-year precipitation concentration variability were also investigated using the precipitation concentration index (PCI) and the coefficient of variation of PCI, respectively. The spatial distributions of intra-annual precipitation variability (or precipitation concentration) and inter-annual precipitation concentration showed a decreasing gradient from the southeast to the northwest. The T-mode principal component analysis (PCA) in association with cluster analysis (CA) was used to delineate homogeneous precipitation sub-zones for simplifying the spatial structure of precipitation variability over the region during the considered period. Results suggest three distinct sub-regions, including the northeastern part (the driest sub-region with the highest precipitation variability), the central and southern parts (the sub-region with the highest degree of seasonality of precipitation), and the northwestern part (the rainiest sub-region with the lowest inter-annual and intra-annual precipitation variability).