Publication Details

Performance Assessment of Three Long-Term Gridded Precipitation Products for Precipitation and Extreme Event Analysis in the Padas River Basin, Malaysia

Gridded precipitation products (GPPs) serve as an important alternative data source in Earth sciences where observational data is limited, particularly in tropical regions. Understanding their reliability is essential for continuous improvement and for guiding researchers in their selection. This study aims to evaluate the performance of APHRODITE, NASA POWER, and ERA5 in estimating precipitation over the Padas River Basin (PRB), a region frequently affected by floods. The assessment covers both overall precipitation variability and extremes, employing continuous and categorical statistical metrics as well as a probability distribution function (PDF). The results show that the GPPs reasonably capture the temporal variability of monthly and annual precipitation from 1990 to 2014, with moderate to high correlation coefficients (CC). However, APHRODITE consistently underestimated precipitation, while NASA POWER tended to overestimate it. Moderate-intensity precipitation (5–20 mm/day) was generally overestimated by the GPPs, resulting in a high detection of precipitation days, but this also caused approximately 40% of non-precipitation days to be misclassified as precipitation days. Moreover, the GPPs were less reliable in capturing precipitation extremes, as reflected in flood-related indices such as maximum one-day precipitation (Rx1day) and the frequency of heavy (R20mm) and extreme (R50mm) precipitation events, with low CC values and underestimated magnitudes. These findings suggest that the evaluated GPPs are appropriate for representing general precipitation patterns but less reliable for calculating precipitation extreme indices. Improvements in retrieval algorithms, observational calibration, and tropical process parameterization are recommended to enhance product reliability in the future.