Abstract
Abstract. Significant progress has been made in identifying the influence of different processes and emissions on the summertime enhancements of free tropospheric ozone (O3) at northern midlatitude regions. However, the exact contribution of regional emissions, chemical and transport processes to these summertime enhancements is still not well quantified. Here we focus on quantifying the influence of regional emissions on the summertime O3 enhancements over the Middle East, using updated reactive nitrogen (NOx) emissions. We then use the adjoint of the GEOS-Chem model with these updated NOx emissions to show that the global total contribution of lightning NOx on middle free tropospheric O3 over the Middle East is about 2 times larger than that from global anthropogenic sources. The summertime middle free tropospheric O3 enhancement is primarily due to Asian NOx emissions, with approximately equivalent contributions from Asian anthropogenic activities and lightning. In the Middle Eastern lower free troposphere, lightning NOx from Europe and North America and anthropogenic NOx from Middle Eastern local emissions are the primary sources of O3. This work highlights the critical role of lightning NOx on northern midlatitude free tropospheric O3 and the important effect of the Asian summer monsoon on the export of Asian pollutants.
Highlights
O3 is produced in the troposphere when volatile organic compounds (VOC) and carbon monoxide (CO) are photochemically oxidized in the presence of NOx
Remote sensing measurements from Tropospheric Emission Spectrometer (TES) show a maximum in summertime free tropospheric O3 over the Middle East (Worden et al, 2009; Liu et al, 2009)
Our results reveal that the global total contribution of lightning NOx on middle free tropospheric O3 over the Middle East is about 2 times larger than that from global anthropogenic sources
Summary
O3 is produced in the troposphere when volatile organic compounds (VOC) and carbon monoxide (CO) are photochemically oxidized in the presence of NOx. Miyazaki et al (2015) obtained significant bias reductions for O3 and nitrogen dioxide (NO2), relative to satellite and ozonesonde measurements Use of their updated NOx emission estimates is, expected to provide a better simulation of tropospheric O3 than the Global Emissions Inventory Activity (GEIA) (Benkovitz et al, 1996) used by Liu et al (2009). In their analysis, Liu et al (2009) used the tagging capability of the GEOS-Chem model to quantify the regional influence on the Middle East O3 maximum, based on the linearized O3 production and loss rate. Following Jiang et al (2015b), we use the adjoint of the GEOS-Chem model to carry out a more detailed sensitivity analysis, which will allow us to better distinguish the contributions of different regions and emission categories to free tropospheric O3 over the Middle East
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