Analyzing the Role of Topography in NO₂ Dispersion: Evidence from the 2021 Manavgat Forest Fire

Abstract. Nitrogen dioxide (NO₂), a major non-greenhouse gas, significantly impacts air quality and human health, particularly in regions affected by large-scale forest fires. The subsequent dispersion of NO₂ plumes is critically influenced by atmospheric conditions and underlying terrain, yet the specific role of topography remains under-explored, particularly in post-fire scenarios. This preliminary study investigates the influence of topographic features on NO₂ dispersion following the major 2021 Manavgat forest fire in Türkiye, utilizing satellite-derived NO₂ concentrations from Sentinel-5P TROPOMI observed during 28th July - 4 August 2021. Topographic variables—elevation, slope, and aspect—were derived from NASA’s SRTM Digital Elevation Model (DEM - 30 m) to characterize the complex terrain. Univariate (UV) Moran’s I was employed to evaluate the spatial autocorrelation of NO₂ concentrations, assessing patterns of clustering or dispersion and their relationship with these terrain variables. Results revealed significant positive spatial autocorrelation, indicating that higher NO₂ concentrations preferentially accumulated in lower elevations and areas with gentler slopes, while the influence of aspect appeared more variable. This suggests that topographic features acted as constraints, potentially trapping the plume and enhancing gas retention near the surface in valleys and flatter regions. These initial findings contribute to a deeper understanding of terrain-atmosphere interactions governing pollutant behavior in post-fire environments and highlight the importance of incorporating topographic parameters into localized air quality monitoring and exposure assessment frameworks.