In the recent decades, poor spatial coverage of rain gauges and weather radars, mostly in less developed countries, has caused satellite-based precipitation products to gain more popularity. However, they are considered less precise compared to traditional rain gauges and weather radars. Therefore, their thorough evaluations are essential before implementing these products in practice. In this study, IMERG satellite-based precipitation product was evaluated in the Fars province, Iran, using daily rain gauges as reference data to find the relationships between the uncertainties in the product and various factors such as elevation, temperature, and rainfall intensity by employing continuous and categorical statistical metrics. The findings revealed that: a) The IMERG product overestimates light rainfall and underestimates heavy rainfall, while showing the best performance in the range 40–80 mm/day. b) The accuracy of the product tends to vary in different months of the year and it is less biased in ones with milder temperatures. c) Higher correlation in mid-elevated areas (up to 0.96), positive bias in low-elevated areas (up to 2.5) and negative bias in high-elevated areas (down to −0.4) were observed. d) A considerable improvement in the IMERG estimates was observed for longer time scales for almost all validation indices. Overall, IMERG products show potential for hydrological and atmospheric decision-making, but further improvements in retrieval algorithms and developing local correction models, considering the trends found in this study, are needed for increased reliability.

近几十年来，雨量计和天气雷达的空间覆盖范围较差（主要在欠发达国家），导致卫星降水产品越来越受欢迎。然而，与传统雨量计和天气雷达相比，它们被认为不太精确。因此，在实践中实施这些产品之前，他们的彻底评估至关重要。本研究在伊朗法尔斯省对IMERG卫星降水产品进行了评估，以日雨量计为参考数据，通过采用连续和分类统计指标。研究结果表明： a) IMERG 产品高估了小雨量，低估了大雨量，同时在 40-80 毫米/天范围内表现出最佳性能。b) 产品的准确度在一年中的不同月份往往会有所不同，并且在气温较温和的月份中偏差较小。c）观察到中高地区的相关性较高（高达0.96），低海拔地区的正偏差（高达2.5）和高海拔地区的负偏差（低至-0.4）。d) 对于几乎所有验证指数，在更长的时间尺度上观察到 IMERG 估计值有了相当大的改进。总体而言，IMERG 产品显示了水文和大气决策的潜力，但考虑到本研究中发现的趋势，需要进一步改进检索算法和开发局部校正模型，以提高可靠性。