Simulation of carbon monoxide transport during April 1994

The Multiscale Air Quality Simulation Platform (MAQSIP) is used to stimulat e transport of carbon monoxide (CO) as a passive tracer over North America, Europe, and the North Atlantic during the April 1994 Measurement of Air Po llution from Satellites (MAPS) mission. MAQSIP is driven by meteorological fields generated by the Pennsylvania State University/National Center for A tmospheric Research fifth-generation mesoscale model. Model CO surface emis sions from biomass burning, fossil fuel combustion, nonmethane hydrocarbon oxidation, oceans, and soils are based on inventories from the Belgian Inst itute for Space Aeronomy and the Global Emissions Inventory Activity. Predi cted CO mixing ratios are vertically weighted for comparison with MAPS obse rvations. The spread in the mission-averaged vertically weighted simulated CO mixing ratios (similar to 38 ppbv, compared to 60 ppbv in the MAPS data) suggests that CO surface emissions significantly affect MAPS observations on a weekly timescale. Good qualitative agreement is found between MAPS obs ervations and model predictions on several temporal and spatial scales. Pos sible reasons for discrepancies are examined. A simulation without cumulus convection increases CO mixing ratios in the lower model layers and deplete s CO above, resulting in a complex pattern of increases and decreases upon vertical weighted integration. Another simulation, which included a diurnal emissions variation, produced significant changes in instantaneous local C O mixing ratios, but had a minimal effect on the mission-averaged MAPS comp arisons.