Regional modeling of enhanced upper tropospheric ozone due to biomass burning and lightning in Central Africa during the 2006 AEROSE II Cruise

Ozonesonde measurements from the AEROSE II Cruise observed enhanced ozone in the upper troposphere off the coast of West Africa during June 2006. While stratospheric intrusions, nitrogen oxides from Sahalian soils, biogenic emissions from Central African rainforests, anthropogenic emissions from urban areas (i.e. Lagos) are prominent sources of upper tropospheric ozone over the eastern Atlantic Ocean, in quantity none of these outweigh the convective transport of biomass burning (bb) tracers. Nitrogen oxides from lightning (LNOx) are thought to be secondary sources of ozone in this region. Aircraft observations, global modeling, and recently mesoscale modeling studies have been done. Despite this, there are no firm quantities of the LNOx contribution. This study will use the regional model, WRF-Chem for the dates of 20 May to 1 July 2006 to attain first order estimates of the ozone concentrations and bb tracers such as CO. To do this, the difference in CO and ozone concentrations will be calculated between a bb model simulation containing year 2000 RETRO monthly averaged anthropogenic emissions, MEGAN biogenic emissions, and 2006 GFEDv2 8-Julian day averaged fire emissions and a control run where the anthropogenic and biogenic emissions are kept as background but the fire emissions are taken away. To examine the horizontal and vertical transport from via convective transport, CO and ozone concentrations will be interpolated to pressure surfaces and examined with Hovmoller diagrams at specific points and over 30-40 degree longitude slices. Secondly, first order estimates of the LNOx ozone contribution with a LNOx parameterization inside WRF-Chem. Here, the cloud-to-ground (CG) lightning strikes observed by WWLLN are scaled up to the total (combination of CG and intra-cloud (IC) lightning) observed by TRMM-LIS. The LNOx emissions will be assigned to the grid boxes of each of the scaled-up total lightning strokes horizontally and vertically based on whether or not the grid boxes are of a marine or continental cli mate, or a combination of both. The profiles are based on Ott et al. 2009. The differences in NOx and ozone concentrations in the upper troposphere will be examined by calculating differences between the LNOx parameterization simulation versus the control simulation and versus the bb simulation. These difference calculations will give first order percentage increases of the bb tracer and LNOx ozone over the background.