Variabilities in ozone at a semi-urban site in the Indo-Gangetic Plain region: Association with the meteorology and regional processes

摘要: [1] The Indo-Gangetic Plain (IGP) region is one of the most densely populated regions in World, but ground-based observations air pollutants are highly limited this region. Here, surface ozone made during March 2009–June 2011 at a semi-urban site (Pantnagar; 29.0°N, 79.5°E, 231 m amsl) IGP presented. Ozone mixing ratios show daytime photochemical buildup with levels sometimes as high 100 ppbv. Seasonal variation 24-h average shows distinct spring maximum (39.3 ± 18.9 ppbv May) while (1130–1630 h) an additional peak autumn (48.7 ± 13.8 November). The daytime, not daily average, observed seasonality agreement space-borne OMI tropospheric column NO2, TES CO (681 hPa), nearby altitude (Nainital) central Himalayas and to extent results from global chemistry transport model (MATCH-MPIC). It suggested that mainly due photochemistry, involving local small-scale dynamical processes. Biomass burning activity over northern Indian could act source precursors spring. seasonal estimated be 32–41 9–14 August–September. A correlation analysis between Pantnagar Nainital along depth data suggests emissions processes influence quality pristine Himalayan region, particularly midday hours evening rate change (8.5 hr−1) higher than morning change, which dissimilar those other urban or rural sites. different southern India. Results MATCH-MPIC capture overestimate levels. Model simulated H2O2/HNO3 suggesting NOx-limited regime. chemical box (NACR Master Mechanism) used further corroborate using set sensitivity simulations, estimate integrated net production day (72.9 ppbv) site.