Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Atmos. Chem. Phys., 17, 14393-14413, 2017
https://doi.org/10.5194/acp-17-14393-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
05 Dec 2017
WRF-Chem simulated surface ozone over south Asia during the pre-monsoon: effects of emission inventories and chemical mechanisms
Amit Sharma1,2, Narendra Ojha2, Andrea Pozzer2, Kathleen A. Mar3, Gufran Beig4, Jos Lelieveld2,5, and Sachin S. Gunthe1 1Department of Civil Engineering, Indian Institute of Technology Madras, Chennai, India
2Atmospheric Chemistry Department, Max Planck Institute for Chemistry, Mainz, Germany
3Institute for Advanced Sustainability Studies, Potsdam, Germany
4Indian Institute for Tropical Meteorology, Pune, India
5Energy, Environment and Water Research Center, The Cyprus Institute, Nicosia, Cyprus
Abstract. We evaluate numerical simulations of surface ozone mixing ratios over the south Asian region during the pre-monsoon season, employing three different emission inventories in the Weather Research and Forecasting model with Chemistry (WRF-Chem) with the second-generation Regional Acid Deposition Model (RADM2) chemical mechanism: the Emissions Database for Global Atmospheric Research – Hemispheric Transport of Air Pollution (EDGAR-HTAP), the Intercontinental Chemical Transport Experiment phase B (INTEX-B) and the Southeast Asia Composition, Cloud, Climate Coupling Regional Study (SEAC4RS). Evaluation of diurnal variability in modelled ozone compared to observational data from 15 monitoring stations across south Asia shows the model ability to reproduce the clean, rural and polluted urban conditions over this region. In contrast to the diurnal average, the modelled ozone mixing ratios during noontime, i.e. hours of intense photochemistry (11:30–16:30 IST – Indian Standard Time – UTC +5:30), are found to differ among the three inventories. This suggests that evaluations of the modelled ozone limited to 24 h average are insufficient to assess uncertainties associated with ozone buildup. HTAP generally shows 10–30 ppbv higher noontime ozone mixing ratios than SEAC4RS and INTEX-B, especially over the north-west Indo-Gangetic Plain (IGP), central India and southern India. The HTAP simulation repeated with the alternative Model for Ozone and Related Chemical Tracers (MOZART) chemical mechanism showed even more strongly enhanced surface ozone mixing ratios due to vertical mixing of enhanced ozone that has been produced aloft. Our study indicates the need to also evaluate the O3 precursors across a network of stations and the development of high-resolution regional inventories for the anthropogenic emissions over south Asia accounting for year-to-year changes to further reduce uncertainties in modelled ozone over this region.

Citation: Sharma, A., Ojha, N., Pozzer, A., Mar, K. A., Beig, G., Lelieveld, J., and Gunthe, S. S.: WRF-Chem simulated surface ozone over south Asia during the pre-monsoon: effects of emission inventories and chemical mechanisms, Atmos. Chem. Phys., 17, 14393-14413, https://doi.org/10.5194/acp-17-14393-2017, 2017.
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We evaluate the numerical simulations of surface ozone during pre-monsoon season against a network of stations including clean, rural and polluted urban environments in the south Asian region. Significant effects of the employed emission inventory and chemical mechanism on the simulated ozone are found during the noon hours of intense photochemistry. The presented evaluation on the diurnal timescale would have implications for assessing ozone buildup and impacts on human health and crop yields.
We evaluate the numerical simulations of surface ozone during pre-monsoon season against a...
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