Direct estimation of the rate constant of the reaction ClO + HO2 → HOCl + O2 from SMILES atmospheric observations 1Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, Kanagawa 226-8503, Japan
09 Jan 2014
2National Institute of Information and Communications Technology (NICT), Nukui-kita, Koganei, Tokyo, 184-8795, Japan
3Alfred Wegener Institute for Polar and Marine Research, Potsdam, Germany
Received: 03 April 2013 – Published in Atmos. Chem. Phys. Discuss.: 14 May 2013 Abstract. Diurnal variations of ClO, HO2, and HOCl were
simultaneously observed by the Superconducting Submillimeter-Wave
Limb-Emission Sounder (SMILES) between 12 October 2009 and 21 April 2010.
These were the first global observations of the diurnal variation of
HOCl in the upper atmosphere. A major reaction for the production of HOCl
is ClO + HO2 → HOCl + O2 (Reaction (R1)) in extra-polar regions. A model study suggested that in the
this is the only reaction influencing the amount of HOCl during the night. The
evaluation of the pure reaction period, when only Reaction (R1)
occurred in the Cly chemical system, was performed by checking the
consistency of the HOCl production rate with the ClO
loss rate from SMILES observation data. It turned out that the SMILES
data at the pressure level of 0.28 hPa (about 58 km) in the autumn
mid-latitude region (20–40°, February–April 2010) during night (between
modified local time 18:30 and 04:00) were suitable for the estimation
of the rate constant, k1. The rate constant obtained from SMILES observations was
k1(245 K) = (7.75 ± 0.25) × 10−12 cm3 molecule−1 s−1. This result is consistent
with results from a laboratory experiment and ab initio calculations for
similar low-pressure conditions.
Revised: 29 November 2013 – Accepted: 29 November 2013 – Published: 09 January 2014
Citation: Kuribayashi, K., Sagawa, H., Lehmann, R., Sato, T. O., and Kasai, Y.: Direct estimation of the rate constant of the reaction ClO + HO2 → HOCl + O2 from SMILES atmospheric observations, Atmos. Chem. Phys., 14, 255-266, doi:10.5194/acp-14-255-2014, 2014.