Summertime carbon dioxide and ozone fluxes and resistances in a neighborhood of Chicago

In urban areas elevated concentrations of CO2 and O3 are expected. Data on ozone concentrations is collected routinely in many cities, attention to CO2 concentrations in urban areas has, so far, been fairly limited and restricted to a small number of studies of spatial patterns within an urban area at different times of day and year, and temporal patterns at single points for short periods of time. In urban environments, for neither gas has attention been directed to the actual surface-atmosphere fluxes. Here we report the results of an observational study of summertime CO2 and O3 fluxes for a suburb of Chicago, Illinois. Two ATI three-dimensional sonic anemometer thermometers (SAT) were mounted on mobile towers at 18 and 27 m, 2.1 and 3.1 times the height of the roughness elements, zH, respectively. In addition, a 1 dimensional CSI SAT, a CSI krypton hygrometer, and the inlet to a teflon tube, which pulled air to a closed path infra red gas analyzer (IRGA) (Licor model LI-6262) and a Scintrex LOZ-3 to observe ozone via a chemoluminescent technique, were located at 3.1 zH. These data are used to derive deposition velocities and resistances to transport. Here attention is directed to the magnitude of the values determined, and the impact of assumptions made in their derivation.