Monday, 11 January 2016: 4:00 PM
Room 356 ( New Orleans Ernest N. Morial Convention Center)
We have developed a capability to simulate the methane-carbon monoxide-hydroxyl radical (CH4-CO-OH) system within the NASA Global Modeling and Assimilation Office (GMAO) GEOS-5 atmospheric general circulation model. A parameterization of OH is used to capture nonlinear chemical feedbacks of the CH4-CO-OH system in a computationally-efficient way, allowing for simulation of many decades of this system and many sensitivity simulations. Concentrations of OH in the troposphere are calculated as a function of a set of meteorological, solar irradiance, and chemical variables, including CH4 and CO. The module includes a wetland CH4 emission parameterization based on soil temperature and precipitation with sensitivities derived from a process-based wetland emission model that allows for further coupling of the methane and climate simulations. We run the model for a historical period (1988-present) as well as a future projection (through 2050) with various emissions scenarios, including an alternative interannually varying wetland CH4 emissions distribution from the TransCom-CH4 study in addition to our parameterized wetland emissions. We evaluate our simulated distributions of atmospheric CH4 against ground-based observations and satellite data sets, including SCIAMACHY and GOSAT. The model captures much of the observed spatial and temporal variations in CH4, with largely similar variability for the two different wetland emissions estimates though with differing trends over the historical period. The model CH4 lifetime with respect to removal by OH is generally within the range estimated by previous model and observation-based studies. We discuss the contributions of model sources, sinks, and transport to the variability.
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