METO 621The Ozone HoleDecline in mean October ozone levels over Halley BayOzone concentrations over Syowa StationSchematic of the winter polar vortexOzone HoleClO and O3 in mid-SeptemberPartitioning of ChlorinePolar Stratospheric CloudsSlide 10Overall chemistry within the vortexOzone loss within the Arctic VortexTemperature and chlorine monoxide in the ArcticTotal Ozone Field March 11, 1990 Nimbus 7 TOMSLatitudinal Average for Total Ozone March 11, 1990Total ozone with seasonal component removedTotal Mass of OzoneDynamics versus ChemistryMETO 621Lesson 23The Ozone HoleDecline in mean October ozone levels over Halley BayOzone concentrations over Syowa StationSchematic of the winter polar vortexOzone HoleClO and O3 in mid-SeptemberPartitioning of ChlorinePolar Stratospheric Clouds•There are two main classes of PSC.•Type 1 PSC are small (<1m) HNO3 rich particles. These have a mass mixing ratio of about 10 ppbm.•Type II PSC are larger (from 10 m to about 1 mm) composed primarily of H2O-ice with minor amounts of HNO3 as hydrates.•They can constitute up to 1000 ppbm of the stratosphere.•As noted before, the primary reaction that can be induced on the surface of the PSC isClONO2 + HCl → Cl2 + HNO3•The HNO3 is then retained in the PSC.Polar Stratospheric Clouds•The overall catalytic cycle is2(Cl+O3 → ClO + O2) ClO + ClO + M → (ClO)2 + M (ClO)2 + h → Cl + ClOO ClOO + M → Cl + O2 + M net 2O3 → 3O2Overall chemistry within the vortexOzone loss within the Arctic VortexTemperature and chlorine monoxide in the ArcticTotal Ozone Field March 11, 1990 Nimbus 7 TOMS(Hudson et al., 2003)Latitudinal Average for Total OzoneMarch 11, 1990(Hudson et al., 2003)Total ozone with seasonal component removedLINEAR FITSOverall (black) 3.2% decadePolar (Blue)2.5% per decadeMid-latitude (Green)2.2 per decadeTropical (Red)1.9% per decadeLinear fit from Jan 1979 to May 1991Total Mass of Ozone•The difference between the overall and regime trends can be explained by looking at the equation for the total mass of ozone: M = AΩ0 = APΩP + AMΩM + ATΩT +AAΩA –A =total area between 25 and 60°N, and Ω0 = overall mean column ozone –AP, AM, AT = regime areas ΩP, ΩM, ΩT= regime mean column ozone •One can get a trend if the regime Ω varies with time, or the regime A varies with time, or bothDynamics versus Chemistrychemistry. to70% and dynamics, to due is trend theof 30%about then thisdo weIf.chemistry it toassign weso )boundaries (fixed area relative fixed a has termsecond The dynamics. it toassign will weso valueozone fixed a haspair each of first term Theetc ......... dtd:get we wrt timeatingDifferentiarea. relative theis Where:equation previous therearrangecan