Assessing how Annual Precipitation is Driven by the Wettest Days using IMERG Earth Observation Data

In the context of global warming, daily precipitation extremes are becoming increasingly frequent and severe, further exacerbating the uneven distribution of daily precipitation throughout the year. The number of Wettest Days that contribute to 50% of the annual precipitation (WD50) is a key metric for understanding how annual precipitation is disproportionately driven by a small number of days, with significant implications for climate science and water resource management. Despite its importance, there remains limited research on WD50, particularly from the vantage point of satellites. Therefore, our study leverages NASA’s Integrated Multi-satellitE Retrievals for Global precipitation measurement mission (IMERG) to examine global patterns in WD50. IMERG data reveal substantial variability in WD50 across reference climate regions worldwide, with lower WD50 values in dry areas and higher values in wetter ones. Comparison with over 31000 rain gauges in the Global Historical Climatology Network (GHCN) confirms IMERG’s alignment with ground data at specific locations (R² between 0.49 to 0.68).  This analysis demonstrates IMERG’s capability to capture the wettest days as key contributors to annual precipitation. Furthermore, our research provides new insights into the heterogeneous distribution (spatially) in precipitation unevenness (temporally), which is essential for understanding regional rainfall patterns and their intensification in response to climate change.