Precipitation is an essential climate and forcing variable for modeling the global water cycle. Particularly, the recent Integrated Multi-satellite Retrievals for GPM (IMERG) product retrospectively provides an unprecedented two decades of high-resolution satellite precipitation estimates. The primary goal of this study is to examine the similarities and differences between the two latest and also arguably the most popular, GPM IMERG Early and Final Run (ER and FR) products across the globe. The results reveal that: (1) ER systematically estimates 12.0% higher annual rainfall than FR, particularly over land (16.7%); (2) ER and FR show significant differences in instantaneous rates (Root Mean Squared Difference: RMSD = 2.38 mm h⁻¹ and normalized RMSD: RMSD_norm = 1.09), especially in Africa (RMSD = 2.40 mm h⁻¹) and hot, arid regions (RMSD_norm = 1.11), but less so in Europe (RMSD = 2.16 mm h⁻¹) and cold areas (RMSD_norm = 0.87); and (3) ER measures 33.0% higher extreme rainfall rates than FR over the globe. The exploration of their similarities and differences provides a first-order global assessment of various hydrological utilities: FR is designed to be more suitable for retrospective hydroclimatology and water resource applications, while the earliest available ER product, though not bias-corrected by rain gauges, still shows potential utility for operational modeling of rainfall-triggered hazards. The findings of this study can provide an assessment to product developers and broader data users and practitioners to address the inherent issues in hardware limitations, retrieval algorithms, and uncertainty quantification for research and applications.

降水是模拟全球水循环的重要气候和强迫变量。特别是，最近的GPM综合多卫星检索（IMERG）产品可追溯地提供前所未有的两十年的高分辨率卫星降水估计。这项研究的主要目的是研究全球范围内两种最新的，也可以说是最受欢迎的GPM IMERG早期和最终运行产品（ER和FR）之间的异同。结果表明：（1）ER系统估计年降水量比FR高12.0％，特别是在陆地上（16.7％）；（2）ER和FR的瞬时速率存在显着差异（均方根差：RMSD = 2.38 mm h ^-1和归一化RMSD：RMSD_norm = 1.09），尤其是在非洲（RMSD = 2.40 mm h^-1）和炎热干燥的地区（RMSD_norm = 1.11），但在欧洲则少得多（RMSD = 2.16 mm h ^-1）和寒冷地区（RMSD_norm = 0.87）；（3）ER在全球范围内测得的极端降雨率比FR高33.0％。对它们的异同的探索提供了对各种水文实用性的一阶全局评估：FR被设计为更适合追溯水文气候学和水资源应用，而最早可用的ER产品，尽管没有通过雨量计进行偏差校正，仍然显示了对降雨触发的危害进行操作建模的潜在效用。这项研究的结果可以为产品开发人员以及更广泛的数据用户和从业人员提供评估，以解决硬件限制，检索算法以及不确定性量化的固有问题，以进行研究和应用。