 Solution

Under the proposed steady balance,The air number density cancels from the ratio. ThereforeThe reservoir relaxation test for a chemical steady state gives a hydrogen chloride relaxation time of $1/(k_{10}[\mathrm{OH}])=1.53\times 10^6\mathrm{s}\simeq 17.7$ days. Hydrogen chloride is a reservoir rather than a rapidly equilibrating radical. A steady state is plausible only if chlorine abundance, methane, hydroxyl radical and transport vary slowly compared with several weeks. It is doubtful during rapid vortex breakdown and reservoir reformation, precisely when production and mixing are changing. The numerical hydroxyl radical value is conditional on the steady-state hypothesis, not an independent measurement of hydroxyl radical.