<![CDATA[This paper analyzed tropospheric ozone (O3) and precursor variability, examined ENSO effects through drought and fire, and evaluated differences in O3 responses between areas with contrasting anthropogenic activity in East Kalimantan during 2005–2024. The datasets included O3, NO2, CO, HCHO, the Oceanic Nino Index (ONI), SPI-1, MODIS hotspots, and population density. Analyses used the Mann–Kendall test, Sen’s slope, cross-correlation, fixed-effects panel regression, and 500-replication bootstrap validation. O3, NO2, and HCHO showed no significant long-term trends, whereas CO decreased significantly by 0.357 ppbv year−1. Seasonality differed among gases: CO peaked in JJA, HCHO in MAM, and NO2 and O3 in SON. ENSO was negatively correlated with SPI-1 at lag 0 (r = −0.477) and positively correlated with hotspots at lag 1 (r = 0.669). All three indirect ENSO pathways to O3 were significant, with drought mediation largest (β = 0.031). In low-anthropogenic areas, O3 responded to ONI_lag, CO, NO2, SPI-1, and hotspots, whereas high-anthropogenic areas were mainly associated with ONI_lag and CO.]]>
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