Evaluation statistically of temperature and precipitation datasets with observed data in Iran

This study aimed to present Climatic Research Unit (CRU) data and assess the accuracy of this data with the latest GPCC updates against the synoptic stations data during 2014-1985 have been done. For this purpose, monthly precipitation from GPCC Full Data Version 7, monthly precipitation and temperature from CRU TS3.23 with 0.5 × 0.5 0degree spatial resolution, monthly total precipitation, average of minimum, maximum and mean daily temperature of 88 synoptic stations with proper distribution in Iran were gathered and analyzed. To assess the databases that mentioned, R square, RMSE, IA, Bias, Slope of the regression and EF indicators was used. Statistical comparisons revealed that, although accuracy of CRU precipitation dada in Iran, especially in the western half of country, is well, but in some regions, especially coastal areas, is less reliable. Because the R square in these areas is less than 0.5, while the accuracy of GPCC data in all areas of Iran even coastal stations is very high. So that, the amount of its precipitation in different regions of Iran is very close to the amount of precipitation recorded in the synoptic stations. Temperature components (average, minimum and maximum) assessment shows that although CRU amounts in the Caspian coastal area have more deviation than other areas, but, more than 95% of the observed data variance across the country explained by CRU and most of the CRU data distributed around the regression line. This terms represents very high accuracy and reliability of CRU gridded temperature data in Iran. Based on the results of this study suggested that in the regions with no data, GPCC precipitation data and CRU temperature data to be used.