A physics-informed geospatial machine-learning downscaling framework for improving extreme rainfall
Kunlong He , Dongmei Zhao , Xiaohong Chen , Qingsong Xu , Wei Zhao , Qiuhua Liang , Yanhui Zheng , Quanxi Shao
Geography and Sustainability ›› 2026, Vol. 7 ›› Issue (4) : 100513
Reliable high-resolution precipitation is essential for monitoring hydrologic extremes and informing climate-risk decisions, yet satellite precipitation products often show biases and remain too coarse (5–25 km) to resolve localized processes. Conventional downscaling also tends to overlook dynamic moisture–cloud mechanisms that drive precipitation variability. We develop a Physics-Informed Geospatial Machine-Learning Downscaling rainfall model (PIGMLD) to produce 1-km daily precipitation over China (2000–2020) by combining the 10-km Global Precipitation Measurement (GPM) Integrated Multi-satellitE Retrievals for GPM (IMERG) (GPM IMERG) product with rare ground observations, ERA5-Land precipitation, and physically traceable covariates describing moisture, clouds, and land–atmosphere coupling. Evaluation against independent gauges across China and nine major river basins shows broad skill gains: 84.1 % of stations achieve KGE > 0.60, with improved event detection and reduced systematic bias. Gains are constrained by complex topography and sparse in-situ stations in the Northwest and Southwest basins (median RMSE = 1.18 mm; KGE = 0.45). For heavy and torrential rainfall, RMSE decreases by 36.1 % and 28.3 %, respectively. Relative threshold assessments indicate robust corrections under dry and wet extremes: for events below the 10th percentile, BIAS is reduced by ∼66.7 % at > 90 % of stations; for events ≥ 90th percentile, underestimation is substantially alleviated, with BIAS typically reduced by ∼50.1 %. XGBoost–SHAP attribution reveals scale-dependent controls: 10-km estimates are dominated by cloud and column moisture, whereas 1-km estimates are more sensitive to near-surface humidity and land-surface states, and heavy rainfall reflects coupled moisture–dynamics–thermodynamics interactions. Overall, PIGMLD provides a mechanism-aware pathway for producing and interpreting 1-km precipitation fields and clarifies when finer-scale information improves extreme-event characterization.
Rainfall / Physics-informed geospatial machine-learning downscaling / Data fusion / Extremes / Governing factors
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