MIPAS confirms Stimpfle et al. formation rates for HOCL

The figures show the temporal evolution of daytime HOCl in the Antarctic polar vortex in 2002.

The current JPL recommendation (small circles in right panel) for rate constants of the reaction ClO + HO2 -> HOCl + O2 fail to reproduce MIPAS measurements (solid dots), while good agreement can be achieved with the Stimpfle et al. (1979) rate constants (large circles).

Further it could be shown that in the polar vortex the HOCl layer is built up predominantly by the indirect heterogeneous chemistry from HO2 and heterogeneously generated ClO rather than directly by heterogeneous reaction of water droplets or ice and chlorine nitrate.

Reference: http://www.atmos-chem-phys.net/9/1817/2009/acp-9-1817-2009.html