First measurements of ClOOCl in the stratosphere: The coupling of ClOOCl and ClO in the Arctic polar vortex

• Published in: Journal of Geophysical Research - Atmospheres Vol. 109; no. D3; pp. D03301 - n/a
• Main Authors: Stimpfle, R. M., Wilmouth, D. M., Salawitch, R. J., Anderson, J. G.
• Format: Journal Article
• Language: English
• Published: American Geophysical Union 16-02-2004; Blackwell Publishing Ltd
• Subjects: Atmospheric Composition and Structure; Chemical kinetic and photochemical properties; chlorine dimer; Instruments and techniques; Middle atmosphere—composition and chemistry; photochemistry; stratosphere
• ISSN: 0148-0227; 2156-2202
• DOI: 10.1029/2003JD003811

The first measurements of ClOOCl in the stratosphere have been acquired from a NASA ER‐2 aircraft, deployed from Kiruna, Sweden (68°N, 21°E), during the joint SOLVE/THESEO‐2000 mission of the winter of 1999/2000. ClOOCl is detected by thermal dissociation into two ClO fragments that are measured by the well‐known technique of chemical conversion, vacuum ultraviolet resonance fluorescence. Ambient ClO is detected simultaneously. Observations of the ratio [ClOOCl]/[ClO]2 (estimated uncertainty of ±25%, 1 σ) are used with a time‐dependent photochemical model, to test the model representation of the ratios of kinetic parameters J/kProd and kLoss/kProd for day and nighttime observations, respectively. Here, kProd and kLoss are the rate constants for ClOOCl production and loss, respectively, and J is the photolysis rate of ClOOCl. The observations are in good agreement with J based upon the 2002 JPL recommended cross sections for ClOOCl [Sander et al., 2003], if the true value of kProd is given by either the 2000 JPL recommendation [Sander et al., 2000] or the work of Trolier et al. [1990]. The larger values of kProd given by Bloss et al. [2001] and the 2002 JPL recommendation are consistent with the observations only if J is increased by a significant amount. This is accomplished if J is calculated with the larger ClOOCl cross sections measured by Burkholder et al. [1990]. The J values for ClOOCl based on the Huder and DeMore [1995] cross sections are too small, by factors of ∼1.6 to 2.5 for all values of kProd, based on the observations. Nighttime results suggest that, for 190 < T < 200 K, the values for KEq (the equilibrium constant, equal to the ratio of kProd/kLoss) of Cox and Hayman [1988] and Avallone and Toohey [2001] are in best agreement with the observations.