Impacts of Central American Fires on Ozone Air Quality along the US Gulf Coast

Biomass burning in Central America is associated with agriculture activities and occurs regularly during April and May every year. Satellite observations have documented frequent transport of wildfire smoke from Mexico and Central America to the southern US, causing haze and exceedance of fine particle matter. However, the impacts of those fires on surface ozone in the US are poorly understood. This study uses both observations and modeling to examine the effects of the springtime Central America fire emissions on surface ozone over the Gulf coastal regions over a long-term time period (2002-2015). Passive tracer simulation in the nested-grid version of the GEOS-Chem chemical transport model over North America is used to identify the days when Central American fire plumes reached the US Gulf Coast. During the identified fire-impact days, Central American fires are estimated to result in an average of 9 ppbv enhancement of regional background ozone over the Houston-Galveston-Brazoria (HGB) region. Satellite-observed distributions of AOD and CO are used to examine the transport pathways and effects of those fires on atmospheric composition. Finally, we integrate satellite observations, ground measurements, and modeling to quantify the impact of Central American fires on springtime ozone air quality along the US Gulf Coast in terms of both long-term (2002-2015) mean and extreme cases.