Threshold-driven responses of air pollutants and greenhouse gases to meteorological conditions

Meteorological variability exerts strong control over atmospheric ventilation and photochemical environments, altering how air pollutants and greenhouse gases accumulate and transform independently of emission changes. Yet these meteorological controls on air quality remain insufficiently quantified, particularly under compound extremes. Here, we integrate multi-sensor satellite observations with meteorological reanalysis to examine how atmospheric conditions regulate urban air pollutant and greenhouse gas variability over north-central India during March 2022–February 2025. Daily conditions over Delhi NCR and Agra are classified into Normal, Stagnation, Heatwave, and Photochemical regimes using boundary layer height, wind speed, temperature, solar radiation, and a ventilation index. Stagnation conditions are associated with the strongest amplification of short-lived pollutants, with black carbon and nitrogen dioxide increasing by 84% in Agra and 78% in Delhi NCR, and nitrogen dioxide increasing by 30% in Agra and 80% in Delhi NCR relative to Normal conditions. Heatwave conditions suppress primary pollutant accumulation through enhanced mixing but modestly enhance ozone via intensified photochemistry. Photochemical conditions selectively amplify ozone (~7%) without corresponding increases in primary pollutants, while methane remains largely invariant. These findings demonstrate that meteorology-driven changes in atmospheric dispersion and radiative forcing can substantially modulate air quality independently of emission trends, highlighting the need to incorporate ventilation-sensitive metrics into air-quality management and meteorology-informed mitigation strategies.