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Two-decades of GPM IMERG Early and Final Run Products Intercomparison: Similarity and Difference in Climatology, Rates, Extremes and Hydrologic Utilities
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  • Zhi Li,
  • Guoqiang Tang,
  • Zhen Hong,
  • Mengye Chen,
  • Shang Gao,
  • Pierre-Emmanuel Kirstetter,
  • Jonathan Gourley,
  • Teshome Yami,
  • Yang Hong
Zhi Li
University of Oklahoma Norman Campus

Corresponding Author:[email protected]

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Guoqiang Tang
Tsinghua University
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Zhen Hong
University of Oklahoma Norman Campus
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Mengye Chen
The University of Oklahoma
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Shang Gao
University of Oklahoma
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Pierre-Emmanuel Kirstetter
University of Oklahoma
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Jonathan Gourley
National Severe Storms Lab
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Teshome Yami
University of Oklahoma Norman Campus
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Yang Hong
School of Civil Engineering and Environmental Sciences, University of Oklahoma
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Abstract

Precipitation is an essential climate and forcing variable for modeling the global water cycle. Particularly, the Integrated Multi-satellitE Retrievals for GPM (IMERG) product retrospectively provides unprecedented two-decades of high-resolution satellite precipitation estimates (0.1-deg, 30-min) globally. The primary goal of this study is to examine the similarities and differences between the two latest and also arguably most popular GPM IMERG Early and Final Run (ER and FR) products systematically over the globe. The results reveal that: (1) ER systematically estimates 13.0% higher annual rainfall than FR, particularly over land (13.8%); (2) ER and FR show less difference with instantaneous rates (Root Mean Squared Difference: RMSD=2.38 mm/h and normalized RMSD: RMSD_norm=1.10), especially in Europe (RMSD=2.16 mm/h) and cold areas (RMSD_norm=0.87); and (3) with similar detectability of extreme events and timely data delivery, ER is favored for use in hydrometeorological applications, especially in early warning of flooding. Throughout this study, large discrepancies between ER and FR are found in inland water bodies, (semi) arid regions, and complex terrains, possibly owing to morphing differences and gauge corrections while magnified by surface emissivity and precipitation dynamics. 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 management, while the earliest available ER product, though not bias-corrected by ground gauges, shows suitable applicability in operational modeling setting for early rainfall-triggered hazard alerts.