Geographical Research

Nowadays، undoubted access to up to date with high spatial resolution and low temporal resolution of meteorological parameters is a one of the necessary needs for meteorological science researches. In order to doing this research have been used the different daily، monthly and yearly Iran precipitation from global and regional data base of GPCP، GPCC، Aphrodit V101 0.25، Aphrodit V101 0.5 و Aphrodit V1003 0.25. The amount of precipitation and its changes based on cited data base has been calculated and with compared with Iran Asfezari and Station data base during 1979 to 2004. Thus the one time daily، monthly and yearly series extracted for every data base. The nonparametric Mann Kendal method fitted on the series and the change rate calculated by Sen method. The results showed that exist significant correlation between Iran Asfezari and Station data base and other data base. The correlation between Iran Asfezari with other data base is more than Station data base. The Iran Asfezari data base show highest correlation with Global Precipitation Climatology Center (GPCC). The results from trend analysis showed that Iran's precipitation changes trend in May and July are significant. The trend of precipitation in May is negative while in July trend is positive. The annual precipitation based on the whole of the data base is negative but not significant. Overall the comparison between precipitation data base showed that for studding Iran's precipitation characters، global and regional data base cited in this study are very useful and valuable.