| Summary: | Stratospheric measurements of NO, NO_(2), O_(3), ClO, and HO_(2) were made during spring, early summer, and late summer in the Arctic region during 1997 as part of the Photochemistry of Ozone Loss in the Arctic Region in Summer (POLARIS) field campaign. In the sunlit atmosphere, NO_(2) and NO are in steady state through NO2 photolysis and reactions involving O_(3), ClO, BrO, and HO_(2). By combining observations of O_(3), ClO, and HO_(2), observed and modeled values of the NO_(2) photolysis rate coefficient (JNO_(2)), and model estimates of BrO, several comparisons are made between steady state and measured values of both NO_(2) and JNO_(2). An apparent seasonal dependence in discrepancies between calculated and measured values was found; however, a source for this dependence could not be identified. Overall, the mean linear fits in the various comparisons show agreement within 19%, well within the combined uncertainties (±50 to 70%). These results suggest that photochemistry controlling the NO_(2)/NO abundance ratio is well represented throughout much of the sunlit lower stratosphere. A reduction in the uncertainty of laboratory determinations of the rate coefficient of NO + O_(3) → NO_(2) + O_(2) would aid future analyses of these or similar atmospheric observations. © 1999 American Geophysical Union. Manuscript Accepted: 13 April 1999; Manuscript Received: 4 December 1998. he authors gratefully acknowledge T. F. Hanisco and E. J. Lanzendorf for use of the HO_(x) data set, J. C. Wilson and C. A. Brock for use of the aerosol data set, and P. A. Newman for the calculation of the solar exposure parameter. This work was supported by the NASA Upper Atmosphere Research Program, Atmospheric Chemistry and Modeling and Analysis Program, and the Atmospheric Effects of Stratospheric Aircraft Project of the NASA High Speed Research Program. Published - jgrd6659.pdf
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