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Twilight observations suggest unknown sources of HO_x

Wennberg, P. O. and Salawitch, R. J. and Donaldson, D. J. and Hanisco, T. F. and Lanzendorf, E. J. and Perkins, K. K. and Lloyd, S. A. and Vaida, V. and Gao, R. S. and Hintsa, E. J. and Cohen, R. C. and Swartz, W. H. and Kusterer, T. L. and Anderson, D. E. (1999) Twilight observations suggest unknown sources of HO_x. Geophysical Research Letters, 26 (10). pp. 1373-1376. ISSN 0094-8276. doi:10.1029/1999GL900255.

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Measurements of the concentrations of OH and HO_(2) (HO_(x)) in the high-latitude lower stratosphere imply the existence of unknown photolytic sources of HO_(x). The strength of the additional HO_(x) source required to match the observations depends only weakly on solar zenith angle (SZA) for 80° < SZA < 93°. The wavelengths responsible for producing this HO_(x) must be longer than 650 nm because the flux at shorter wavelengths is significantly attenuated at high SZA by scattering and absorption. Provided that the sources involve only a single photon, the strength of the bonds being broken must be < 45 kcal mole^(−1). We speculate that peroxynitric acid (HNO_4) dissociates after excitation to an unknown excited state with an integrated band cross section of 2-3 × 10^(−20) cm^(2) molecule^(−1) nm (650 < λ < 1250 nm).

Item Type:Article
Related URLs:
URLURL TypeDescription
Wennberg, P. O.0000-0002-6126-3854
Hanisco, T. F.0000-0001-9434-8507
Cohen, R. C.0000-0001-6617-7691
Anderson, D. E.0000-0002-8310-0554
Additional Information:© 1999 American Geophysical Union. Received December 21, 1998; revised March 12; accepted March 24, 1999. Paper number 1999GL900255. We thank NASA's Upper Atmosphere Research and the Atmospheric Effects of Aviation Programs for supporting the POLARIS field campaign (M. Kurylo, P. DeCola, and R. Kawa, project managers). POW acknowledges additional support from the NSF (ACM-9612282) for this work. DJD acknowledges NSERC for partial support of this work. VV acknowledges NSF for support. We thank C. Webster (for CH_(4) and CO), R. May (for H_(2)O), J. Margitan and M. Proffitt (for O_(3)), C. Wilson and C. Brock (for aerosol surface area), J. Elkins and E. Atlas (for organic halogens), L. Thomason (for aerosol extinction), R. McPeters (O_3 column and reflectivity), and M. Mlynczak and B. T. Marshall(for O_(2)(b^(1)Σ_(g))). We appreciate the leadership of D. Fahey and P. Newman, POLARIS lead scientists. We thank A. Tuck for motivating this study. A portion of this work was performed at JPL under contract from NASA.
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Natural Sciences and Engineering Research Council of Canada (NSERC)UNSPECIFIED
Issue or Number:10
Record Number:CaltechAUTHORS:20140716-085906258
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ID Code:47256
Deposited On:16 Jul 2014 22:52
Last Modified:10 Nov 2021 17:37

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