WRF-Chem Model Estimates of Tropospheric Ozone Production Over the Tropical Atlantic Ocean from Lightning NOx and Biomass Burning and Comparisons with Ozonesonde and Remote Sensing Data

Tropospheric ozone is a major greenhouse gas globally and is abundant in the upper troposphere (UT) in the vicinity of 20°W–25°W off the coast of West and Central Africa. Ship-based ozonesonde launches from the AEROSE II Cruise in June and early July 2006, the Southern Hemisphere Additional Ozonesonde (SHADOZ) Network, and the 2006 AMMA Wet–Season Campaign show robust signals of ozone enhancement. Possible sources of these enhancements in UT ozone include lightning-induced nitrogen oxides (LNO_x) and biomass burning (bb) emissions over continental Africa. In my doctoral work, I completed 20 km WRF-Chem simulations (Smith, 2012) and show that ozone enhancement in the lower troposphere over the Gulf of Guinea is primarily from Southern Hemispheric biomass burning (bb). Across the entire Equatorial Atlantic Ocean, with increasing altitude LNO_x emissions contribute increasingly more to ozone. Determining the dominant source of this ozone provides the motivation to refine the estimates of LNO_x production with a high-resolution numerical model such as the Chemistry Version of the Weather Research and Forecasting Model. These experiments will be done at a 20 km resolution and a domain of 30°E to 30°W and 15°N to 15°S for June–August 2006, and will compare the production and transport of nitrogen oxides (NO_x) based on observed lightning flash locations to that using model parameterized lightning. These simulations will extend through the period of the AMMA airborne campaign. Data from the Ozone Measuring Instrument (OMI) for ozone, NASA Level 2 OMI Version 2 for NO₂, the Measurements of Pollution in the Troposphere Instrument (MOPITT) on the Terra satellite for CO, and the Microwave Limb Sounder CO and ozone will be used to evaluate the model simulations. Averaging kernels and scattering weights will be applied for this comparison.