Evaluation of sub-daily satellite precipitation products and their representation of the diurnal cycle in a tropical island environment

Sub-daily rainfall data are crucial for understanding flood risk and the diurnal cycle of precipitation. This study evaluates the performance of sub-daily satellite precipitation estimates from GSMaP (version 6) and IMERG (version 7b) against rainfall measurements from three rain gauges in the Northern Range, Trinidad from 2020 to 2021. Comparisons were conducted at various temporal aggregations (1-hr, 3-hr, 6-hr, and 12-hr) using continuous and categorical statistical metrics and graphical assessments. The results revealed that IMERG detects substantially more rainfall events than GSMaP at all temporal scales, while GSMaP estimates higher frequencies of trace precipitation. Both IMERG and GSMaP have higher PODs in the wet seasons than in the dry seasons. In comparison to rain gauge measurements over the entire study period, IMERG generally captures the midday peak well, extending it over a broader time period (1 h), while GSMaP estimates a delayed peak at 13:00. Overall, the findings highlight some of the strengths and limitations of these sub-daily satellite-precipitation products for flood-related applications in a data-sparse mountainous region of Trinidad.