|IDSO, CRAIG - ARIZONA STATE UNIV
|BALLING JR, ROBERT - ARIZONA STATE UNIV
Submitted to: Journal of Physical Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/15/1998
Publication Date: N/A
Interpretive Summary: Atmospheric carbon dioxide concentrations were measured at one-mile intervals prior to sunrise and in the middle of the afternoon on a number of different transects through the metropolitan area of Phoenix, Arizona. Maps of the data reveal the existence of an urban CO2 dome over the city. Carbon dioxide concentrations at the center of the dome are as much as 45% greater than those observed over surrounding rural areas in the morning and as much as 25% greater in the afternoon. These high CO2 concentrations, which are produced primarily by the burning of fossil fuels such as gas and oil, have the ability to enhance the growth of urban vegetation and provide some protection against the debilitating effects of local air pollution. Hence, some of the positive effects of one of the major end-products of the combustion process (CO2) tend to counteract one of the negative effects of some of the minor by-products of that same process (air pollution).
Technical Abstract: Near-surface air temperatures, relative humidities and atmospheric carbon dioxide concentrations were measured at 1.6-km intervals prior to sunrise and in the middle of the afternoon on five days in January along a number of different transects through the Phoenix metropolitan area. Spatially interpolated maps of the data indicate the presence of an urban C02 dome that reaches concentrations as high as 610 ppmv in the city center and decreases to a value of approximately 425 ppmv on the outskirts of the city. Pre-dawn CO2 values inside the dome are considerably higher than mid-afternoon values, suggesting that solar-induced convective mixing plays a significant role in diurnally redistributing the anthropogenically-produced CO2 that accumulates near the surface during the night and early morning hours. Temperature and relative humidity appear to have little influence upon either the concentration or location of the CO2 dome, but variations in wind speed and direction may at times disrupt the pattern that develops under normally fair conditions.