28 Nov 2022
28 Nov 2022

Variable effects of spatial resolution on modeling of nitrogen oxides

Chi Li1, Randall V. Martin1, Ronald C. Cohen2,3, Liam Bindle1, Dandan Zhang1, Deepangsu Chatterjee1, Hongjian Weng4, and Jintai Lin4 Chi Li et al.
  • 1Department of Energy, Environmental Chemical Engineering, Washington University in St. Louis, St. Louis, MO, USA
  • 2Department of Chemistry, University of California, Berkeley, Berkeley, CA, USA
  • 3Department of Earth and Planetary Science, University of California, Berkeley, Berkeley, CA, USA
  • 4Laboratory for Climate and Ocean-Atmosphere Studies, Department of Atmospheric and Oceanic Sciences, School of Physics, Peking University, Beijing, China

Abstract. The lifetime and concentration of nitrogen oxides (NOx) are susceptible to non-linear production and loss, and con- sequently to the resolution of a chemical transport model (CTM). Here we use the GEOS-Chem CTM in its high performance implementation (GCHP) to investigate NOx simulations over the eastern United States across a wide range of resolutions (13–181 km). Following increasing grid size, daytime surface NOx concentrations over July 2015 generally decrease over the Great Lakes (GL) region and increase over the Southern States (SS), yielding regional biases (181 km vs. 13 km) of −18 % to 9 %; meanwhile hydrogen oxide radicals (HOx) increase over both regions, consistent with their different chemical regimes. Night- time titration of ozone by surface nitric oxide (NO) was found to be more efficient at coarser resolutions, leading to longer NOx lifetimes and higher surface concentrations of nitrogen dioxide (NO2) over the GL in January 2015. The tropospheric NO2 column density at typical afternoon satellite overpass time has spatially more coherent negative biases (e.g., −10 % over the GL) at coarser resolutions in July, which reversed the positive biases of surface NOx over the SS. The reduced NO2 aloft (> 1 km altitude) at coarser resolutions was attributable to the enhanced HOx that intrudes into the upper troposphere. Application of coarse resolution simulations for interpreting satellite NO2 columns will generally underestimate surface NO2 over the GL and overestimate surface NO2 over the SS in summer, while uniformly overestimating NOx emissions over both regions. This study significantly broadens understanding of factors contributing to NOx resolution effects, and the role of fine resolution to accurately simulate and interpret NOx and its relevance to air quality.

Chi Li et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2022-1191', Anonymous Referee #1, 22 Dec 2022
  • RC2: 'Comment on egusphere-2022-1191', Anonymous Referee #2, 23 Dec 2022

Chi Li et al.


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Short summary
Models are essential to diagnose the significant effects of nitrogen oxides (NOx) on air pollution. We use an air quality model to illustrate 1) the variability of NOx resolution-dependent simulation biases; 2) how these biases depend on specific chemical environments, driving mechanisms, and vertical variabilities; and 3) how these biases affect the interpretation of satellite observations. High resolution simulation is thus critical to accurately interpret NOx and its relevance to air quality.