Statistical Characteristics of Extreme Precipitation Events Over Tropical Oceans and Land Using Five Years of IMERG Data

This study provides a statistical analysis of tropical extreme precipitation events (EPEs) using five
years (2006-2010) of IMERG V06 Final Run data. EPE life cycles and spatial structures are
tracked with a Lagrangian algorithm that allows spatial and temporal gaps and captures both light
and heavy/extreme precipitation. Across the tropics, we identify 6.84 million EPEs (~3.99 million
oceanic and ~2.85 million land) and examine their frequency and key characteristics, including
duration, intensity, rainfall, and areal coverage, over tropical land and oceans. Geographic and
seasonal patterns follow major convective regions, such as the ITCZ, with event counts migrating
meridionally alongside the seasonal progression of tropical rainfall. Local event counts are dominated by 1–6-h events everywhere, while 6–12-h events make up a higher percentage over
land. Diurnal cycles differ sharply: land EPEs peak in the afternoon, whereas oceanic events
exhibit weaker morning and late-evening peaks. Substantial land-ocean contrasts also emerge in
EPE properties. Oceanic 6–24-h events exhibit larger median and interquartile ranges of areal
coverage, extreme rainfall, and total rainfall than their land counterparts, whereas for 1–6-h events
the opposite holds. Relationships between areal coverage and total rainfall are broadly linear across
several orders of magnitude, with upper bounds consistently larger over the ocean. Instantaneous
attributes show similar linearity but greater scatter and comparable upper bounds across land and
ocean, highlighting the role of duration in controlling rainfall. These results suggest that EPE
characteristics are shaped by local environments and may respond differently to climate change
over land and ocean.