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Published November 15, 1994 | Published
Journal Article Open

The diurnal variation of hydrogen, nitrogen, and chlorine radicals: implications for the heterogeneous production of HNO₂


In situ measurements of hydrogen, nitrogen, and chlorine radicals obtained through sunrise and sunset in the lower stratosphere during SPADE are compared to results from a photochemical model constrained by observed concentrations of radical precursors and environmental conditions. Models allowing for heterogeneous hydrolysis of N₂O₅ on sulfate aerosols agree with measured concentrations of NO, NO₂, and ClO throughout the day, but fail to account for high concentrations of OH and HO₂ observed near sunrise and sunset. The morning burst of [OH] and [HO₂] coincides with the rise of [NO] from photolysis of NO₂, suggesting a new source of HOₓ that photolyzes in the near UV (350 to 400 nm) spectral region. A model that allows for the heterogeneous production of HNO₂ results in an excellent simulation of the diurnal variations of [OH] and [HO₂].

Additional Information

© 1994 American Geophysical Union. Manuscript Accepted: 19 OCT 1994; Manuscript Received: 29 AUG 1994. Paper number 94GL02782. This work was supported by NASA grants NAG2-731, NAGW-1230, NAS1-19955 and NSF grant ATM-89-21119 to Harvard University. We thank J. Herman and the GSFC processing team for providing data from TOMS and P. Newman and R. Nagatani for providing data from NMC.

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August 20, 2023
August 20, 2023