بررسي روش هاي توزيع مكاني بارندگي روزانه و ماهانه در حوضه درياي خزر

Comparison of estimation methods for spatial distribution of daily and monthly rainfall in Caspian sea watershed

Rainfall is one of climatic variables that is very important in soil and water study. Therefore, information on the spatial variation of climatic variables is necessary in such studying. There are several methods to estimate rainfall along which interpolation methods are useful in this regards. In this study, 3 methods were used to estimate daily and monthly rainfall. These methods are: Thin Plate Smoothing Splines (TPSS), Weighted Moving Average (WMA) and Kriging..Cross Validation technique was used for comparison of the above mentioned methods. Variography analysis of daily rainfall showed good spatial correlation in these regions, however logarithmic transform of data showed better spatial correlation. Also, good spatial correlation was observed for July, August, September, October and November. Survey in above methods show that the TPSS method with power of 2 and WMA are the most precise method in estimating daily rainfall (MAE=0.6-1.2 mm). The TPSS method with power of 2 was recognized as the most precise method in estimating monthly rainfall (MAE values for monthly rainfall was calculated between 7 and 45 mm).