The Measurement of Air Pollution From Satellites (MAPS) experiment measured global distributions of carbon monoxide (CO) while on board the space shuttle during April 9--19 and September 30 to October 11, 1994. This paper examines selected examples of the meteorological processes that contributed to the observed signals. We first examine and relate the mean distribution of MAPS-measured CO, surface station-measured CO, streamlines, and divergent winds averaged over the two missions. Tropical high CO values were associated with boundary layer convergence regions, particularly in October, that enable CO associated with biomass burning to reach the free troposphere where it can be detected by the nadir viewing gas filter 4.7 μm radiometer. CO values over northern middle latitudes show evidence of fossil fuel pollution especially in April. Southern middle and high latitudes in April suggest photochemical control, while in October these regions are strongly influenced by the tropical biomass burning. Next, we consider events on 1 day near the center of each mission and show that in one of these cases, low CO measurements are associated with high potential vorticity, which suggests that the air samples originated from the stratosphere. Finally, we modify the two mean patterns, both within 23 days of the equinox, to illustrate the possible separation of the natural photochemical CO pattern from the CO pollution patterns. This procedure brings out the intercontinental and transcontinental transport of pollution in April northern hemisphere middle and high latitudes as well as, less markedly, in the October maps. It also accentuates the biomass burning contribution in October and shows pollution to extend southeastward from South America into the South Atlantic and also from Australia into the South Pacific. The separation is made possible by having CO measurements with global coverage. ¿ 1999 American Geophysical Union