ENSO-Induced Variabilities in Tropical Tropospheric Composition: Observed and Modeled Evaluation of the 2006 El Nino and 2007 La Nina

Recent studies have shown that the El Niño-Southern Oscillation (ENSO) is a major driver of interannual variability in tropospheric ozone, suggesting that ENSO-related changes in tropospheric column ozone (TCO) are tied to changes in large-scale atmospheric circulation patterns and, to a lesser degree, changes in biomass burning and lightning. The relative roles of these processes in determining tropical tropospheric atmospheric composition during an El Niño (October-December 2006) and a La Niña (October-December 2007) time period are investigated herein using "replay" simulations with the NASA GEOS-5 Chemistry Climate Model (CCM); satellite retrievals from MOPITT, TES, AIRS, and MLS; and ozone profiles from MOZAIC and SHADOZ. The work presented will examine (1) the contribution of biomass burning, dynamics, and lightning-NO emissions to observed perturbations in tropospheric composition during both 2006 and 2007; (2) the impact of El Niño-driven biomass burning on tropospheric CO as viewed by satellite products with differing resolutions; and (3) the pros and cons of placing lightning-NO emissions at the location of model convection as opposed to the location where flashes most commonly occur. Preliminary CCM results indicate that biomass burning increased monthly-averaged mid-tropospheric CO amounts over the Maritime Continent by as much as ~400 ppbv during October 2006, representing nearly 100% of the total ENSO-related changes in CO for this month.