GPCP Version 3.3: A Refined Global View of Precipitation from Satellite and Gauge Observations

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Abstract The Global Precipitation Climatology Project (GPCP) Version 3.3 provides an upgraded global precipitation record from January 1983 (monthly) and January 1998 (daily) to the delayed present, both at 0.5° × 0.5° resolution. Major updates include new input datasets from orbital passive microwave (PMW) and combined PMW–radar retrievals, geostationary infrared (IR) imagery, GPCC Version 2022 gauge analyses, and an updated Merged CloudSat–TRMM–GPM (MCTG) climatology, with IR estimates recalibrated using updated Special Sensor Microwave Imager (SSMI) and Special Sensor Microwave Imager/Sounder (SSMIS) adjustments. A new absolute bias error field provides a direct estimate of systematic uncertainty. The Daily product inherits these improvements and integrates IMERG Version 07B Final Run, with GridSat IR data extending coverage back to January 1998. Relative to Version 3.2, GPCP V3.3 exhibits systematically higher precipitation, primarily over the oceans, yielding a global mean of 3.06 mm day −1 for 1992–2023 (an 8.5% increase over V3.2 and 4.4% over ERA5). Comparisons with independent oceanic benchmarks (PALs and PACRAIN atolls) indicate a modest positive bias in V3.3 but more consistent behavior than ERA5, which is more sensitive to the choice of which of the two reference datasets are used. GPCP V3.3 shows weak global trends with regionally significant changes and modest increases in heavy precipitation frequency and intensity relative to V3.2.

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