Interannual Variability and Trends of CH4, CO and OH using the Computationally-Efficient CH4-CO-OH (ECCOH) Module

The methane, carbon monoxide and hydroxyl radical (CH4-CO-OH) atmospheric system is nonlinear and determines the global tropospheric oxidizing capacity. In this study, we implemented the computationally Efficient CH4-CO-OH Module (ECCOH) into the NASA GEOS-5 Atmospheric Global Circulation Model (GEOS-5 AGCM). We investigated the key processes that affected the observed CH4, CO and OH trends and variability from 1988-2008. The simulated surface concentrations of methane and CO, using constant and variable emission scenarios, have been compared and contrasted with that from the in situ measurements. Simulated CH4 dry column is compared to that of the SCIAMACHY while the CO total column is compared to that of TES/MLS and MOPITT. We present our results of the sensitivity of methane, CO, and OH spatial and temporal distributions to the various causal factors that influence them, such as emissions, the overhead ozone column, lightning NO emissions, etc. We demonstrate the importance of using variable emissions and OH to drive the chemistry climate models given that recent modeling studies tend to use constant emissions of CO, and/or CH4 and and/or OH chemistry.