Topographic and seasonal modulation of satellite precipitation errors in the Yangtze River Delta: a cross-scale analysis for climate adaptation

This study evaluates Global Precipitation Measurement Mission (GPM) and Tropical Rainfall Measuring Mission (TRMM) 3B42 products in the Yangtze River Delta using observations and statistics. The results demonstrate that (1) GPM shows superior performance in detecting trace precipitation, while TRMM performs better for light-moderate rain, both exhibiting significant errors for heavy rainfall; (2) GPM achieves optimal performance during December–February and April, whereas TRMM shows better accuracy in April–May but errors in March, August and October, with GPM’s retrieval skill declining markedly in summer while TRMM maintains relatively stable performance; (3) Topographic analysis indicates that both products perform well in low-elevation regions, with TRMM demonstrating greater stability at lower altitudes and GPM showing reduced errors at higher elevations. Optimal retrieval accuracy occurs within the 0–5° slope range, where GPM outperforms TRMM in complex terrain. TRMM performs best on southeastern slopes, whereas the GPM excels on northwestern slopes, which are associated with its dependence on passive microwave retrievals. These findings advance satellite precipitation error characterisation by quantifying physically modulated biases, which is critical for climate adaptation strategies. High spatiotemporal resolutions of the GPM mission support urban flood early-warning systems in coastal megacities, whereas TRMM’s stable climatology aids reservoir operations in monsoon-driven basins.