- 1Department of Environmental Sciences, Deshbandhu College, University of Delhi, New Delhi, India
- 2School of GeoSciences, University of Edinburgh, Edinburgh, EH9 3FF, UK
- 3School of Earth and Environment, University of Leeds, Leeds, LS2 9JT, UK
- 4National Centre for Earth Observation, University of Leeds, Leeds, L22 9JT, UK
- 5Lancaster Environment Centre, Lancaster University, Lancaster, UK
- 6School of Environmental Sciences, Jawaharlal Nehru University, New Delhi, India
South and East Asia (S/E Asia), home to nearly half the world's population, are major contributors to global nitrogen oxide (NOx = NO + NO2) emissions due to recent rapid industrialization, urbanization, and growth in energy consumption. We compare tropospheric column NO2 in the United Kingdom Chemistry and Aerosol (UKCA) model v11.0 with satellite measurements from NASA’s Earth Observing System (EOS) Aura satellite Ozone Monitoring Instrument (OMI) to investigate the seasonality and trends of tropospheric NO2 over S/E Asia. UKCA is the atmospheric composition component of the UK Earth System Model (UKESM). UKCA was run with nudged meteorology, producing hourly output over S/E Asia for 2005–2015. OMI averaging kernels have been applied to the model hourly data sampled at Aura’s local overpass time of 13:45 ± 15 to allow consistent model-data comparison. Background UKCA and OMI tropospheric column NO2 typically ranges between 0 – 2 × 1015 molecules/cm2. Diurnal cycles and vertical profiles of the tropospheric NO2 column in UKCA show that the daily minimum tropospheric column NO2 occurs around the satellite overpass time. UKCA captures the seasonality but overestimates NO2, by a factor of ~2.5, especially during winter over E China and N India, at times and locations with high aerosol loadings. Heterogeneous chemistry is represented in the version of UKCA used here as uptake of N2O5 on internally generated sulfate aerosol. However, aerosol surface area may be underestimated in polluted locations, contributing to overestimation of NO2. In addition, the model may underestimate emissions of volatile organic compounds and associated peroxy acetyl nitrate (PAN) formation, leading to insufficient long-range transport of oxidised nitrogen, also contributing to overestimation of NO2 over polluted regions and underestimation over remote regions. Quantifying and understanding discrepancies in modelled NO2 warrant further investigation as they propagate into modelling of multiple environmental issues.
Keywords: Tropospheric NO2; UKCA Model; Air Quality; Satellite Data; Climate Modelling
How to cite: Pandey, A. K., Stevenson, D., Zhao, A., Pope, R., Hossaini, R., and Kumar, K.: Tropospheric NO2 over South and East Asia measured by OMI and modelled by UKCA, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-975, https://doi.org/10.5194/egusphere-egu25-975, 2025.
