Modeling Rainfall in the West and Southwest of Caspian Sea in GIS Environment, with using Spatial Interpolation Methods

The effect of atmospheric phenomena on the earth and nature and consequently on the human life has reached to the extent that lack of management and knowledge in this sector will cause great expenses in this part. The study area with regard to its dominant topographic and climate condition is not excluded from this rule and each year (in watery seasons) the occurrence of heavy rains causes flood, landslide and erosion of fertilized soils. So estimation of precipitation distribution in the region can help the managers substantially to provide proper planning to prevent the damage. In this study, firstly by using geo statistical methods, while the average precipitation of the areas with no station was estimated, also their accuracy was calculated by using different statistical methods(MAE, MBE, and MSE Error). Based on the obtained results weighted inverse distance methods, linear, circular and exponential kriging threshold in the study area had respectively better interpolation results than the other methods. Therefore, with attention to the results, for modeling rainfall and estimating the mean rainfall in the regions with no station, weighted inverse distance method was used. Therefore the monthly, seasonal and annual precipitation of the study area were prepared. So the studies showed that Caspian Sea systems has the greatest effect on the study area in October, November and December months(autumn season) and causes heavy precipitations in the region.