Summary of all the precipitation products.

Accurate precipitation data is essential for understanding land surface processes and the hydrological cycle, particularly in Southeast Asia (SEA), where precipitation patterns are influenced by complex climatic interactions. This study evaluates the monthly performance of five widely-used daily precipitation products—CPC, CHIRPS, IMERG, ERA5, and PERSIANN—against the benchmark SAOBS dataset over SEA from January 2001 to December 2017. By aggregating daily data into monthly values, we identify the strengths and weaknesses of each product in capturing the spatial and temporal characteristics of precipitation in the tropical region. The evaluation includes analyses of data population, spatial distribution, and temporal variability at a monthly scale. Our findings reveal significant spatial heterogeneity in the performance of these products, emphasizing the importance of scale-specific assessments before their application in regional studies and management practices. Results indicate that the CPC product generally provides the most accurate monthly estimates, with the highest correlation coefficients and lowest root-mean-square errors. However, all products exhibit systematic biases, such as overestimation in high-rainfall regions and seasonal discrepancies. These findings underscore the need for regional calibration to improve the applicability of precipitation products for monthly-scale climate studies and resource management in SEA.精准的降水数据是解析陆地表面过程与水文循环的关键支撑，尤其在东南亚（Southeast Asia, SEA）地区——该区域的降水格局受复杂气候交互作用影响显著。本研究以基准数据集SAOBS为参照，针对2001年1月至2017年12月东南亚区域的逐日降水数据，评估了CPC、CHIRPS、IMERG、ERA5及PERSIANN这5套主流逐日降水产品的月度表现性能。通过将逐日数据聚合为月度均值，本研究厘清了各产品在捕捉热带区域降水时空特征方面的优劣特点。本次评估涵盖了月度尺度下的数据总体特征、空间分布与时间变异性分析。研究结果显示，各产品的表现存在显著空间异质性，这凸显了在将其应用于区域研究与管理实践前，开展针对性尺度评估的重要性。结果表明，CPC产品整体的月度降水估算精度最优，其相关系数最高，均方根误差最低。但所有产品均存在系统性偏差，例如在高降水区域存在高估现象，且存在季节偏差。上述研究结果凸显了开展区域校准的必要性，以提升降水产品在东南亚地区月度尺度气候研究与资源管理中的适用性。