Climatology of the diurnal cycle of precipitation in the Colombian Andes according to ERA5 (1980-2020)

Abstract Precipitation is a critical driver of the hydrological cycle in the mountainous Colombian Andes (mCA), yet its diurnal organization remains complex due to significant orographic modulation. The diurnal cycle of precipitation in the mCA is investigated using 41 years of hourly ERA5 reanalysis data ( $$0.25^\circ $$ resolution) for the 1980-2020 period. The methodology focuses on high-mountain domains (>1,000 m a.s.l.) and evaluates total, convective, and large-scale precipitation components across annual and seasonal scales. Results demonstrate that the diurnal cycle in the mCA is dominated by a robust afternoon maximum primarily driven by convective processes. These convective peaks are densely concentrated between 1,800 and 3,000 m a.s.l., particularly on middle and upper Andean slopes where topography enhances moisture convergence. Conversely, the large-scale component introduces a secondary, persistent nocturnal and early-morning signal (20:00-06:00 LST) that remains relatively uniform across the altitudinal gradient. Seasonal analysis reveals that the diurnal signal intensifies during the primary rainy periods (MAM and SON), with SON exhibiting the greatest spatial homogeneity and intensity. While ERA5 substantially overestimates absolute precipitation magnitudes relative to independent station and satellite observations available for sub-periods and sub-domains of the study area, its representation of the dominant temporal phase of the diurnal cycle during daytime hours is broadly supported by these same comparisons. ERA5 advances the afternoon precipitation peak relative to IMERG, while reproducing the station-based afternoon peak reasonably well; however, it underrepresents nocturnal precipitation in both comparisons. In conclusion, these findings characterize the interplay between radiative forcing and topographic control in the tropical Andes. This work provides a necessary climatological baseline for improving water resource management, regional climate modeling, and the understanding of topographically-induced rainfall regimes in northwestern South America.