Improved modelling of soil NOx emissions in a high temperature agricultural...

Wang, Y., C. Ge, L. C. Garcia, G. D. Jenerette, P. Y. Oikawa, and J. Wang (2021), Improved modelling of soil NOx emissions in a high temperature agricultural region: role of background emissions on NO2 trend over the US, Environmental Research Letter, 16, 084061, doi:10.1088/1748-9326/ac16a3.

EPA reports a steady decline of US anthropogenic NOx emissions in 2005–2019 summers, while NO2 vertical column densities (VCDs) from the OMI satellite over large spatial domains have flattened since 2009. To better understand the contributing factors to a flattening of the OMI NO2 trends, we investigate the role of soil and lightning NOx emissions on this apparent disagreement. We improve soil NOx emissions estimates using a new observation-based temperature response, which increases the linear correlation coefficient between GEOS-Chem simulated and OMI NO2 VCDs by 0.05–0.2 over the Central US. Multivariate trend analysis reveals that soil and lightning NOx combined emissions trends change from −3.95% a−1 during 2005–2009 to 0.60% a−1 from 2009 to 2019, thereby rendering the abrupt slowdown of total NOx emissions reduction. Non-linear inter-annual variations explain 6.6% of the variance of total NOx emissions. As background emissions become relatively larger with uncertain inter-annual variations, the NO2 VCDs alone at the national scale, especially in the regions with vast rural areas, will be insufficient to discern the trend of anthropogenic emissions.

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Applied Sciences Program (ASP)
Modeling Analysis and Prediction Program (MAP)
Atmospheric Composition
Atmospheric Composition Modeling and Analysis Program (ACMAP)