In recent years, gridded precipitation products have been widely used in hydrology studies and other fields of water sciences. This study evaluated the potential of several gridded precipitation products, including GPCC, TRMM, CRU, ERA-Interim, and ERA5, in trend analysis of precipitation depth and the number of rainy days in various regions of Iran. Moreover, the observational precipitation data of the daily time series were collected from 68 Iranian synoptic stations. The Mann–Kendall test was conducted to determine gridded and observed precipitation trends in the period of 1997 to 2017. The probability of detection (POD) and false alarm ratio (FAR) indices were utilized to compare gridded and observed precipitation trends. Results showed that the best consistency (POD: 52% ~ 80%, FAR: 60% ~ 88%) was observed between the observed trends of the number of rainy days and those obtained by TRMM product over different regions of Iran. Moreover, ERA-Interim offered a better performance (POD: 50% ~ 100%, FAR: 58% ~ 72%) in the trend analysis of precipitation depth in Iran. The consistency between observational and gridded precipitation trends has never been analyzed in Iran at this level; therefore, this is considered a unique analysis. Besides, the generated maps of precipitation products' performance provide a comprehensive view of better water resources management over different regions of Iran.

近年来，网格化降水产品在水文研究等水科学领域得到广泛应用。本研究评估了几种网格降水产品，包括 GPCC、TRMM、CRU、ERA-Interim 和 ERA5，在伊朗各地区降水深度和雨天数趋势分析中的潜力。此外，每日时间序列的观测降水数据是从 68 个伊朗天气站收集的。进行了Mann–Kendall测试以确定1997年至2017年期间的网格化和观测降水趋势。利用检测概率（POD）和误报率（FAR）指数比较网格化和观测降水趋势。结果表明，最佳一致性（POD：52% ~ 80%，FAR：60% ~ 88%) 在观测到的雨天数趋势与伊朗不同地区的 TRMM 产品获得的趋势之间观察到。此外，ERA-Interim在伊朗降水深度趋势分析中表现更好（POD：50%~100%，FAR：58%~72%）。伊朗从未在这个级别分析观测和网格降水趋势之间的一致性；因此，这被认为是一种独特的分析。此外，生成的降水产品性能图提供了伊朗不同地区更好的水资源管理的综合视图。伊朗从未在这个级别分析观测和网格降水趋势之间的一致性；因此，这被认为是一种独特的分析。此外，生成的降水产品性能图提供了伊朗不同地区更好的水资源管理的综合视图。伊朗从未在这个级别分析观测和网格降水趋势之间的一致性；因此，这被认为是一种独特的分析。此外，生成的降水产品性能图提供了伊朗不同地区更好的水资源管理的综合视图。