Global O3-CO Correlations in a Global Model During July-August: Evaluation with TES Satellite Observations and Sensitivity to Emissions

We examine global mid-tropospheric (619 hPa) ozone - carbon monoxide (O3-CO) correlations and its sensitivity to emissions during July - August 2005 in the Global Modeling Initiative (GMI) chemistry and transport model driven by the Modern-Era Retrospective Analysis for Research and Application (MERRA) meteorological data set. We evaluate the simulated O3 with climatological O3 profiles from ozonesonde measurements and satellite tropospheric O3 columns. Model O3-CO correlations are 1). positive in the Northern Hemisphere continental outflow regions with large dO3/dCO enhancement ratios, and in the southern African westerly outflow region and Indonesia with small dO3/dCO enhancement ratios; 2). negative over the Asian continent (including the Tibetan Plateau), Middle East, northern and central Africa, and tropical and subtropical deep convective regions. These patterns are consistent with those derived from collocated measurements of O3 and CO from the Tropospheric Emission Spectrometer (TES) on board NASA's Aura satellite, except over the tropical Atlantic and Pacific. Model sensitivity experiments indicate that fossil fuel emissions are responsible for the positive O3-CO correlations in major continental outflow regions and Europe. Biomass burning emissions lead to the positive correlations in the Southern Hemisphere mid-high latitudes. Biogenic emissions make important contributions to the negative O3-CO correlations over the tropical eastern Pacific. Lightning NOx emissions significantly reduce both the positive O3-CO correlations at mid-high latitudes and the negative correlations in the tropics. The corresponding chemical and transport processes will be discussed.