Polar Stratospheric Clouds are associated with which of the following…

Concept: Polar Stratospheric Clouds (PSCs) form only in the extremely cold polar stratosphere (below about -78°C / 195 K) during the polar winter. Their ice and nitric-acid particle surfaces provide sites for heterogeneous chemical reactions that convert stable chlorine and bromine reservoir compounds into reactive, ozone-destroying forms.

Application: On PSC particle surfaces, stable reservoir gases such as HCl and ClONO2 are converted into more reactive species (e.g., Cl2, HOCl). When sunlight returns in early polar spring, these are photolyzed to release chlorine radicals, which destroy ozone through a catalytic chain reaction (Cl + O3 → ClO + O2, repeating many times per radical). This PSC-driven chemistry is the principal mechanism behind the seasonal Antarctic "ozone hole".

• Flash floods arise from intense surface rainfall overwhelming drainage and terrain — a short-term hydro-meteorological hazard with no link to stratospheric halogen chemistry.

• Acid rain forms in the lower troposphere when sulphur and nitrogen oxides dissolve in atmospheric moisture and fall as precipitation — a ground-level pollutant-deposition issue, not a polar-stratosphere cloud process.

• Photo-chemical smog is also a tropospheric phenomenon, produced when nitrogen oxides and volatile organic compounds react in sunlight near the surface — it adds ozone at ground level rather than destroying it in the stratosphere.

Result: Because PSCs specifically enable the chemistry that depletes stratospheric ozone, they are associated with ozone layer depletion.