Abstract
Tropospheric ozone (O3) negatively impacts human health and is also a greenhouse gas.
Highlights
Tropospheric ozone (O3) is an important atmospheric constituent in the contexts of climate, air quality, and tropospheric chemistry
Whilst the near-real time 5 day forecasts were used to inform the eld team during Atmospheric Reactive Nitrogen over the remote Atlantic (ARNA)-2, here we evaluate the Goddard Earth Observing System Composition Forecast system (GEOS-CF) best estimate of the 3D atmospheric composition; prior to the launch of the forecast, the GEOS-CF runs a short historical simulation with the atmospheric general circulation model forced to the analysed meteorological elds from an assimilated GEOS product[40] and stratospheric O3 is nudged toward the O3 elds produced by the GEOS forward processing (GEOS FP) system, which is constrained by ozone observations from the Microwave Limb Sonder (MLS), Ozone Monitoring Instrument (OMI), and the Ozone Mapping and Pro ler Suite (OMPS).[41,42]
We examined the nitrogen oxides (NOx)/total volatile organic compounds (VOCs) ratios for the different areas and a correlation plot of NOx against total VOC is shown in Fig. S2.† Whilst measurements of only 10 VOCs were made from the whole air samples during this study neglecting potentially important compounds such as furans, the measured ratio is similar for the Senegal (0.93) and Uganda (0.85) res, suggesting that chemistry maybe similar for the two types
Summary
Tropospheric ozone (O3) is an important atmospheric constituent in the contexts of climate, air quality, and tropospheric chemistry. It is estimated that surface emissions from biomass burning contribute $24% to boundary layer O3 over Africa, with a large fraction of this transported away from the continent.[3] O3 production in a smoke plume is a complex process and depends on several factors including the relative composition of re emissions, chemical and photochemical reactions, smoke injection height, aerosol effects on chemistry and radiation, and local and downwind meteorological conditions Biomass burning encompasses both natural- and human-induced res, and there remains signi cant uncertainty in the global estimates of emission factors of O3 precursors (VOCs and NOx) from these sources[4] and in the trends of these emissions over time.[5,6] Emissions of the precursors and the subsequent photochemical O3 formation are observed in different locations and on different scales.[7,8] O en, one of the goals of making the measurements is to assess the skill of regional or global models in predicting O3 in re plumes.[9] Whilst the photochemistry involved in O3 formation through hydroxyl radical (OH) initiated oxidation of VOCs and the reaction of the peroxy radical formed with NO is relatively well understood, models can still struggle to describe the evolution of atmospheric composition in re plumes.[10] These model shortcomings are usually o en attributed to errors in the chemical reaction rates,[11] emissions, resolving plume or lament structures due to spatial (vertical and horizontal) resolution,[12] or meteorology, demonstrating the need for further study
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