Influence of atmospheric boundary-layer dynamics on air quality of the middle- and high-density urban areas of Colombia

The interplay between emissions and atmospheric boundary-layer dynamics shapes urban air quality (AQ) in Colombia's complex topography. This study assesses the influence of the atmospheric boundary layer on AQ across contrasting physiographic regions. The ERA5 reanalysis dataset was used to obtain hourly ABLH and VC estimates for the period 2020–2024, while COSMIC-2 profiles were used to derive Temperature Elevation Profile (TEP) variables, including inversion-base height and thermal gradients. Urban AQ data from 78 monitoring stations were obtained from SISAIRE, focusing on PM₁₀, PM_2.5, and O₃. The analysis combines exceedance rates (98th-percentile thresholds), diurnal and seasonal cycles, nonparametric correlations, and Gaussian linear models stratified by stable/unstable ABL conditions and dry/wet seasons. Our results show frequent exceedances in Antioquia and Bogotá, where PM_2.5 daily exceedance medians reach 1.11 % and 0.87 %, respectively. Norte de Santander exhibits the highest PM_2.5 median exceedance rate (7.18 %), while departments such as Cesar and Magdalena show low-to-moderate levels. O₃ responses are strongly modulated by thermal structure, with direct associations between ABLH, inversion strength, and O₃ peaks, particularly in high-elevation terrains. Physiography and circulation patterns explain regional contrasts, with stagnation-prone basins showing stronger pollution accumulation. We conclude that ventilation conditions strongly influence particulate pollution, whereas peak O₃ is governed primarily by precursor emissions and temperature-driven photochemistry. These findings highlight the need for meteorology-aware AQ management strategies, especially in densely populated Andean basins.