Chemistry of the Earth's gas envelope: photochemistry of ozone, NOx/HOx/VOC cycles driving tropospheric oxidation, stratospheric halogen chemistry, aerosol formation, greenhouse-gas balance. Substrate of climate and air-quality modelling.
atmospheric-chemistry
Chapman mechanism (stratospheric ozone)
Four-reaction cycle forming/destroying stratospheric ozone: O₂+hν→2O (λ<242 nm), O+O₂+M→O₃, O₃+hν→O₂+O, O+O₃→2O₂. Predicts qualitative…
Catalytic ozone destruction (Cl, NO, HO_x)
X + O₃ → XO + O₂; XO + O → X + O₂ (net: O₃ + O → 2 O₂); each X atom destroys ~10⁴–10⁵ O₃ before removal. Active X: Cl (CFC source,…
Tropospheric HO_x chemistry
Hydroxyl radical OH, the 'detergent of the atmosphere', initiates oxidation of almost every VOC and CO. Principal source: O(¹D)+H₂O→2OH.…
Photochemical smog (NO_x + VOC)
Sunlight-driven oxidation of VOCs in NO_x-rich air yields ozone and PAN: RO₂ + NO → RO + NO₂; NO₂ + hν → NO + O; O + O₂ + M → O₃. PM₂.₅ and…
Atmospheric aerosol formation
Nucleation of H₂SO₄–H₂O–NH₃–organic clusters produces ultrafine particles (<3 nm) that grow by condensation and coagulation into CCN.…
Polar-vortex heterogeneous chemistry
On polar-stratospheric-cloud surfaces at <~195 K: HCl + ClONO₂ → Cl₂ + HNO₃. Spring sunlight photolyses Cl₂, launching catalytic O₃…
Greenhouse-gas radiative forcing
Molecules with ro-vibrational IR transitions in the 8–14 μm window (CO₂, CH₄, N₂O, H₂O, CFCs) absorb outgoing thermal radiation. Forcing ΔF…
Atmospheric photolysis (J-values)
First-order photolysis rate J = ∫σ(λ)ϕ(λ)F(λ)dλ with absorption cross-section σ, quantum yield ϕ, actinic flux F. Principal driver of…