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The ratio of a specified downward dry deposition flux to its reference near-surface concentration. It has units of speed but need not be an actual particle settling speed: transfer resistance and surface uptake can both control gas dry deposition.

The atmospheric boundary layer over an ocean surface. A box-model ozone budget can include in-layer production, chemical loss, dry deposition, entrainment from the free troposphere and horizontal Advection. Fixed-depth local steady-state assumptions must be checked against transport and day–night variation.

The observed value is about 4 ppb higher than the local chemical–dry deposition balance predicts. Entrainment from the ozone-richer free troposphere adds a term $(w_e/H)({\chi }_{\mathrm{FT}}-{\chi }_{\mathrm{BL}})$; horizontal Advection can likewise import ozone or longer-lived precursors from other regions. Time dependence, including the day–night cycle of photodissociation and changes in mixing depth, is also omitted. The approximately four-day model adjustment time means that air arriving at the measurement location need not have attained the assumed local steady state. These transport and history terms can raise ozone without changing the given local chemical constants.

Excited $\mathrm{O}({}^{1}D)$ has two competing fates. Collisional deactivation returns ground-state oxygen, which reforms ozone rapidly; reaction with water instead gives net ozone loss and two OH radicals. The chemical branching fraction for the latter isThus only about 4.92% of these ozone photolyses directly lead to the specified net chemical loss; treating every photodissociation as permanent removal would overestimate the sink. The corresponding first-order rate is $J_1{f}_w=9.8361\times 10^{-7}{\mathrm{s}}^{-1}$. Converting the given hydroperoxyl mixing ratio to a concentration gives $[\mathrm{H}{\mathrm{O}}_2]=20\times 10^{-12}[\mathrm{M}]=4.4\times 10^8\mathrm{c}{\mathrm{m}}^{-3}$, so $k_4[\mathrm{H}{\mathrm{O}}_2]=9.6800\times 10^{-7}{\mathrm{s}}^{-1}$.

For a well-mixed marine atmospheric boundary layer of depth $H=2\times 10^5\mathrm{cm}$, the downward surface flux is $v_{\mathrm{dep}}[{\mathrm{O}}_3]$. Dividing by the layer volume per unit area gives a first-order dry deposition rate $v_{\mathrm{dep}}/H=7.5\times 10^{-7}{\mathrm{s}}^{-1}$. The air density cancels on expressing the entire balance in ozone mixing ratio $\chi$:At steady state, with $P_{\chi }=0.25/3600\mathrm{ppb}{\mathrm{s}}^{-1}$,The effective removal time is about 4.28 days. This calculation assumes a uniform layer of the diagnosed depth, fixed chemical conditions and a local time-independent balance.

Ozone in the troposphere is a secondary chemical pollutant and a radiatively active gas. Its abundance reflects photochemical production, chemical loss, dry deposition and transport. The photodissociation of nitrogen dioxide alone is part of a null ozone cycle unless peroxy radicals regenerate nitrogen dioxide without consuming ozone.