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The wave-driven mean stratospheric circulation with tropical ascent and extratropical descent. Changes in wave propagation and momentum deposition can alter its strength and transport times. Its response redistributes ozone and trace gases; local chemistry and transport must be considered together.

The radical $\mathrm{BrO}$ participates in catalytic atmospheric ozone destruction. Its measured abundance is only one partition of the total bromine inventory; precursor delivery, photodissociation and reservoir reactions determine the relation between the two.

For competing irreversible pseudo-first-order channels with rates $k_j$, the fraction following channel $j$ is $f_j=k_j/{\sum }_l{k}_l$ when those conditions stay fixed during the intermediate's lifetime. A photochemical destruction rate must count only branches that actually remove the chosen species after fast recycling. For excited oxygen, collisional deactivation followed by ozone reformation is different from reaction with water to make hydroxyl radicals.

The radical $\mathrm{ClO}$ formed when a chlorine atom reacts with ozone. Its reaction partners and reservoirs depend on altitude and temperature; the chlorine monoxide dimer cycle is important under cold, activated polar conditions.

A low-temperature catalytic ozone destruction pathway involving ClO association to ClOOCl, photodissociation of the dimer and regeneration of chlorine atoms. Combined with two Cl + O3 reactions its net effect is $2{\mathrm{O}}_3\to 3{\mathrm{O}}_2$. Low temperature suppresses thermal dimer dissociation, while sunlight is needed for the photolytic step. Polar stratospheric clouds can activate reservoir chlorine before the sunlit cycle becomes rapid.

A compound composed of carbon, chlorine and fluorine, with no hydrogen. Many such fully halogenated molecules resist lower-atmospheric attack but release reactive chlorine after stratospheric photodissociation, contributing to catalytic ozone destruction.

The chlorine peroxide structure formed by association of two ClO radicals with collisional stabilization. Its low-temperature stability and photodissociation provide a route for catalytic ozone destruction. In a laboratory flow system, changing among three ClO precursors and examining infrared spectra helped distinguish the predominant ClOOCl product from an alternative ClOClO isomer. Product assignment and ultraviolet absorption support the proposed intermediate, but do not alone measure an entire atmospheric cycle's ozone-loss rate.^[ref]

An atmospheric electrical discharge. Its high-temperature chemistry can produce nitrogen oxides, influencing ozone and radical chemistry away from surface emission sources. The ozone response depends on subsequent transport and the local chemical regime.

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.

In the productive mixed-radical pathway, chlorine monoxide and BrO yield chlorine and bromine atoms; subsequent atom reactions with ozone regenerate the oxides. The net cycle consumes two ozone molecules per radical-pair event, giving $L=2k[\mathrm{ClO}][\mathrm{BrO}]$ when the subsequent steps are fast. The branching of a real chlorine monoxide–BrO reaction must be included if not already absorbed into its specified effective rate coefficient.

The atmospheric nitrogen oxide $\mathrm{N}{\mathrm{O}}_2$. Daylight photodissociation forms nitrogen monoxide and an oxygen atom; subsequent third-body recombination with oxygen forms ozone. Whether this makes net ozone depends on the pathway that regenerated nitrogen dioxide.

The atmospheric nitrogen oxide $\mathrm{NO}$. It consumes ozone when converted to nitrogen dioxide by $\mathrm{NO}+{\mathrm{O}}_3\to \mathrm{N}{\mathrm{O}}_2+{\mathrm{O}}_2$, but its oxidation by peroxy radicals instead enables net photochemical ozone production.

A regime in which additional available nitrogen oxides tends to increase net photochemical ozone production when other factors are fixed. Reducing nitrogen oxides generally suppresses that production, but local ozone concentration also depends on transport, deposition and NO titration.

A regime in which additional nitrogen oxides promote net tropospheric ozone production because NO availability limits peroxy-radical oxidation of NO. Reducing NOx then generally lowers ozone production, subject to transport and chemical history. At much larger NOx burdens, OH removal by nitric-acid formation can instead produce a VOC-limited ozone-production regime.

Nonbiological molecular oxygen can accumulate when photochemistry and planetary redox sinks allow it, for example after water photolysis and hydrogen loss. Ozone produced from that oxygen is not independent proof of a biological source. The stellar spectrum, water inventory, atmospheric escape and other gases constrain these interpretations.

An electronically excited atomic oxygen state produced in part by ozone photodissociation. Reaction with water can yield two hydroxyl radicals, while collisional quenching returns the atom to its triplet ground term without the same radical production. Its short-lived steady balance is distinct from the lifetime of ozone or water.

In a direct-beam model with an effective ozone cross section $\sigma$, removal of an overlying column $\Delta N$ multiplies the transmitted photodissociation flux by $e^{\sigma \Delta N}$. A real photodissociation coefficient integrates wavelength-dependent cross section, quantum yield and actinic flux, including scattering and the local radiation field.

A relative measure of stratospheric ozone destruction associated with emissions of a substance, conventionally referenced to CFC-11. It depends on atmospheric survival, transport, halogen delivery and catalytic effectiveness, not only the number of chlorine atoms in the formula. Fluorine-only replacements can have negligible direct ozone-depletion potential while remaining strong greenhouse gases.

A contour plot of a specified ozone outcome against the loadings of nitrogen oxides and volatile organic compounds. The ridge separating opposite NOx sensitivities distinguishes an NOx-limited ozone-production regime from a VOC-limited ozone-production regime. The outcome may be peak concentration, a time-integrated measure or a model production rate; axes and averaging conditions must be stated. A schematic diagram is not a calibrated emissions-response prediction.

Local ozone consumption by the reaction $\mathrm{NO}+{\mathrm{O}}_3\to \mathrm{N}{\mathrm{O}}_2+{\mathrm{O}}_2$. Reducing fresh NO emissions can raise local measured ozone even while decreasing regional ozone production. This distinction matters when interpreting precursor-control experiments and observations.