Why Temporal Scale Matters: Daily Extreme Precipitation Inconsistencies in Fengyun‐2 Quantitative Precipitation Estimation Over the Yangtze River Basin

Abstract

One of the primary missions of the Fengyun‐2 (FY‐2) geostationary satellites is to provide high‐temporal‐ and spatial‐resolution quantitative precipitation estimates (QPEs) over East Asia. However, although FY‐2 products are generated using a unified retrieval framework, their performance may vary substantially across temporal scales, leading to pronounced inconsistencies when sub‐daily estimates are aggregated to the daily scale. In this study, we conduct a comprehensive evaluation of precipitation estimates from FY‐2F, FY‐2G, and FY‐2H over the Yangtze River Basin (YRB) during June 2018–March 2022, with a particular focus on scale‐dependent inconsistencies in extreme precipitation monitoring. The assessment employs a suite of extreme precipitation intensity indices, frequency indices, and consistency metrics to systematically evaluate FY‐2 QPE performance at 1‐, 3‐, 6‐, and 24‐h temporal scales, using ground observations as reference data. The results indicate that FY‐2G consistently outperforms FY‐2F and FY‐2H across most evaluation metrics; however, clear temporal‐scale dependencies are evident for all three products. In particular, daily precipitation derived from 1‐ and 3‐h FY‐2G QPEs exhibits the highest consistency with gauge observations, and within the same satellite product (e.g., FY‐2G), daily extreme precipitation estimates aggregated from the 1‐ and 3‐h retrievals consistently outperform those derived from longer temporal scales. In contrast, RX1day and RX5day derived from all FY‐2 QPEs are substantially underestimated at the official 24‐h timescale across the YRB, and extreme precipitation frequency indices, including consecutive wet days (CWD) and consecutive dry days (CDD), also show pronounced underestimation at the daily scale. At sub‐daily timescales (1‐, 3‐, and 6‐h), FY‐2F and FY‐2H tend to slightly underestimate precipitation over plateau regions, whereas FY‐2G generally exhibits minor overestimation. These results demonstrate that lower temporal aggregation of instantaneous satellite precipitation estimates more closely aligns with the accumulation characteristics of ground‐based rain gauge observations, thereby providing a more reliable representation of daily extreme precipitation. Overall, this study highlights temporal‐scale effects as a key source of uncertainty in FY‐2–based extreme precipitation monitoring. The findings emphasize that daily precipitation derived from finer temporal resolutions, particularly 1‐ and 3‐h FY‐2G QPEs, offers clear advantages over directly provided daily products. This work underscores the necessity of explicitly accounting for scale‐dependent biases and optimizing temporal aggregation strategies to improve the reliability of FY‐2 QPEs, especially for extreme precipitation events over complex terrain.

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