Abstract
This study examined the diurnal variation in rainfall in Kalimantan, focusing on precipitation accumulation (PA), precipitation frequency (PF), and precipitation intensity (PI), using rain gauge data from 103 stations (2016–2022) and Integrated Multi‐Satellite Retrievals for Global Precipitation Measurement Version 07 B (IMERG V07B) for an extended period (2002–2022). The results showed that PA was more closely aligned with PF than with PI, indicating that PF played a dominant role in determining total precipitation across Kalimantan. Diurnal peaks of PA and PF were observed in coastal regions during the late afternoon to early evening (14–19 local standard hours [LST]), whereas inland and mountainous regions experienced these peaks in the early morning (00–03 LST). In contrast, PI exhibited greater spatial and temporal variability, reflecting the influence of localised convective processes. Cluster analysis of PA, PF, and PI identified four distinct regions based on peak time and amplitude, showing a strong dependence on topographic features and distance from the coastline. Short‐duration rainfall events ( 6 h) tended to dominate in inland flat regions, although they were still occasionally observed in mountainous areas during the early morning hours. These patterns were driven by onshore rainfall propagation, as observed in the IMERG time cross‐sections, where rainfall moved inland from the southwestern coast between 18 and 00 LST and persisted over mountainous areas for 1–3 h before propagating northeastward between 03 and 08 LST. Offshore propagation observed in the northwest and southeast regions of Kalimantan between 00 and 06 LST further highlights the role of low‐level wind patterns and local atmospheric convergence in modulating rainfall distribution. This study enhances our understanding of the complex diurnal rainfall patterns in Kalimantan.