Atmospheric processes influencing measured carbon monoxide in the NASA Measurement of Air Pollution From Satellites (MAPS) experiment

The Measurement of Air Pollution From Satellites (MAPS) experiment measured global distributions of carbon monoxide (CO) while on board the space shut tle during April 9-19 and September 30 to October 11, 1994. This paper exam ines 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 w inds averaged over the two missions. Tropical high CO values were associate d with boundary layer convergence regions, particularly in October, that en able CO associated with biomass burning to reach the free troposphere where it can be detected by the nadir viewing gas filter 4.7 mu m radiometer. CO values over northern middle latitudes show evidence of fossil fuel polluti on especially in April. Southern middle and high latitudes in April suggest photochemical control, while in October these regions are strongly influen ced 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 mea surements are associated with high potential vorticity, which suggests that the air samples originated from the stratosphere. Finally, we modify the t wo mean patterns, both within 23 days of the equinox, to illustrate the pos sible separation of the natural photochemical CO pattern from the CO pollut ion patterns. This procedure brings out the intercontinental and transconti nental transport of pollution in April northern hemisphere middle and high latitudes as well as, less markedly, in the October maps. It also accentuat es the biomass burning contribution in October and shows pollution to exten d southeastward from South America into the South Atlantic and also from Au stralia into the South Pacific. The separation is made possible by having C O measurements with global coverage.