III/1 Atmospheric transport and chemistry lecture I.Introduction II.Fundamental concepts in atmospheric dynamics: Brewer-Dobson circulation and waves III.Radiative transfer, heating and vertical transport IV.Stratospheric ozone chemistry

III/2 Processes affecting stratospheric O3 3/1997 3/1999

III/3 IV. Stratospheric ozone chemistry 1.Basic concepts of atmospheric chemistry 2.Ozone chemistry and ozone distribution 3.Sources and distribution of ozone-related species 4.Ozone trends 5.The ozone hole 6.Ion chemistry and solar variation 7.Middle atmosphere processes: sprites, meteors, aurora

III/4 IV. Stratospheric ozone chemistry 1.Basic concepts of atmospheric chemistry

III/5 What goes in ? What goes out ? horizontal / vertical transport What goes on in there ? gas-phase reactions surface reactions ion reactions External forcing ? solar radiation, (solar / magnetospheric particles in polar regions)

III/6 What goes in ? What goes out ? horizontal / vertical transport What goes on in there ? gas-phase reactions surface reactions ion reactions External forcing ? solar radiation, (solar / magnetospheric particles in polar regions) Most commonly, reactions in the stratosphere are neutral gas-phase reactions of two reactants, involving at least one radical

III/7 Second order (bimolecular) reaction reactants A and B form products C and D a,b,c,d: stoechiometric quantity of A, B, C, D

III/8 Second order (bimolecular) reaction Rate R of the reaction: rate of change of A R: [molecules / cm 3 s]

III/9 Second order (bimolecular) reaction Rate R of the reaction: R: [molecules / cm 3 s] k rate constant of the reaction [A] concentration (number density) of A [B] concentration of B

III/10 Second order (bimolecular) reaction Rate R of the reaction: R: [molecules / cm 3 s] rate of change of A

III/11 rate constant k: from laboratory measurements

III/12 rate constant k: from laboratory measurements An estimate of k from collision theory: molecules A and B are hard spheres of radii r A and r B

III/13 rate constant k: from laboratory measurements An estimate of k from collision theory: molecules A and B are hard spheres of radii r A and r B

III/14 activated complex reactants products

III/15 activated complex reactants products E 1 : Activation energy E2 energy gained by reaction  H: reaction enthalpy

III/16 activated complex reactants products E 1 : Activation energy E2 energy gained by reaction  H: reaction enthalpy The reaction takes place if the thermal energy of the reactants is larger than E 1 : k = A* exp(-E 1 /(kT)) Boltzmann factor

III/17 activated complex reactants products E 1 : Activation energy E2 energy gained by reaction  H: reaction enthalpy The reaction takes place if the thermal energy of the reactants is larger than E 1 : k = A* exp(-E 1 /(kT)) Arrhenius-form

III/18 Summary of gas-phase reactions First order (unimolecular) reaction photolysis or thermal decomposition Second order (bimolecular) reaction Three-body reaction

III/19 Summary of gas-phase reactions First order (unimolecular) reaction thermal decomposition pressure and temperature dependent Second order (bimolecular) reaction temperature dependent Three-body reaction pressure

III/20 Summary of gas-phase reactions First order (unimolecular) reaction thermal decomposition pressure and temperature dependent Second order (bimolecular) reaction temperature dependent Three-body reaction pressure and temperature dependent pressure

III/21 Photodissociation J AB : photolysis rate

III/22 quantum yield = 0: AB is not dissociated quantum yield = 1: AB is totally dissociated Photodissociation number of photons absorbed J AB : photolysis rate quantum yield absorption cross section actinic flux

III/23 First-order reaction

III/24 First-order reaction

III/25 First-order reaction Lifetime of A: 

III/26 Second-order reaction Lifetime of A:  Valid if [B] is constant, i.e., if the lifetime of B is larger than the lifetime of A

III/27 Calculating the behaviour of gas [A] d[A] / dt = (sum of formation reactions) – (sum of loss reactions) d[A] / dt =  k ij [C i ][C j ] -  k j [A][C j ] +  J j [C i ] – J A [A] gas-phase production and loss reactions of A photolysis reactions forming and dissociationg A

III/28 IV. Stratospheric ozone chemistry 2.Ozone chemistry and ozone distribution - Oxygen atmosphere - Ozone distribution - Catalytic cycles

III/29 Purely oxygen atmosphere (Chapmann cycle)

III/30 Ozone altitude distribution at 8°N, January 28, 2004 Model result from the modified Leeds-Bremen model Mixing ratio

III/31 Ozone altitude distribution at 8°N, January 28, 2004 Model result from the modified Leeds-Bremen model Mixing ratio Ozone maximum Second ozone maximum

III/32 Ozone altitude distribution at 8°N, January 28, 2004 Model result from the modified Leeds-Bremen model Mixing ratioNumber density

III/33 Ozone altitude distribution at 8°N, January 28, 2004 Model result from the modified Leeds-Bremen model Mixing ratioNumber density Maximum kmMaximum km

III/34 Ozone altitude distribution at 8°N, January 28, 2004 Model result from the modified Leeds-Bremen model Mixing ratioNumber density Maximum km Maximum km  The ozone colume (= total ozone) is dominated by the lower stratosphere

III/35 Purely oxygen atmosphere (Chapmann cycle)

III/36 The Ox-family Ox: reactive oxygen Ox = O + O( 1 D) + O 3 lifetime of family is long, family members transfer into each other in fast reactions

III/37 The Ox-family Ox: reactive oxygen Ox = O + O( 1 D) + O 3 lifetime of family is long, family members transfer into each other in fast reactions formation of Ox loss of Ox

III/38 Photochemical lifetimes of O3, O and Ox compared to horizontal transport u

III/39 Photochemical lifetimes of O3, O and Ox compared to horizontal transport u >40 km: Ox is dominated by transport km: Ox is dominated by chemistry >80 km: Ox is dominated by transport

III/40 Photochemical lifetimes of O3, O and Ox compared to horizontal transport u >40 km: Ox is dominated by transport of ozone km: Ox is dominated by chemistry >80 km: Ox is dominated by transport of O

III/41

III/42 Dynamical control of Ox (ozone) in polar night Dynamical control throughout the upper mesosphere / lower thermosphere Dynamical control in the lower stratosphere

III/43 Dynamical control of Ox (ozone) in polar night Dynamical control throughout the upper mesosphere / lower thermosphere Dynamical control in the lower stratosphere Chemical control from mid- stratosphere to mid-mesosphere

III/44 Dynamical control of Ox (ozone) in polar night Dynamical control throughout the upper mesosphere / lower thermosphere Dynamical control in the lower stratosphere Chemical control from mid- stratosphere to mid-mesosphere Transition zone of transport/chemistry control

III/45 The Ox-family: partitioning of family members

III/46 The Ox-family: partitioning of family members from these equation the partitioning of family members can be calculated if photochemical equilibrium is assumed for O and O( 1 D), i.e,

III/47 The Ox-family: partitioning of family members from photochemical equilibrium

III/48 The Ox-family: partitioning of family members from photochemical equilibrium both O and O(1D) are zero during night-time in the stratosphere: [O 3 ] >> [O](Ox  O 3 ) in the upper mesosphere: [O 3 ] < [O] (Ox  O)

III/49 Altitude distribution of Ox species, 8°N, January 28, 2004 Model result from the modified Leeds-Bremen model (non-equilibrium model) Noon

III/50 Altitude distribution of Ox species, 8°N, January 28, 2004 Model result from the modified Leeds-Bremen model Noon < 50 km: Ox  O 3 > 70 km: Ox  O km: transition zone, O and O 3 O(1D) more than five orders of magnitude smaller

III/51 Altitude distribution of Ox species, 8°N, January 28, 2004 Model result from the modified Leeds-Bremen model NoonNight

III/52 Altitude distribution of Ox species, 8°N, January 28, 2004 Model result from the modified Leeds-Bremen model NoonNight Ox  O 3 up to ~ 75 km

III/53 Diurnal variation of Ox species, 8°N, January 28, 2004 Model result from the modified Leeds-Bremen model 40 km: no diurnal variation of ozone and Ox Ozone O Ox

III/54 Diurnal variation of Ox species, 8°N, January 28, 2004 Model result from the modified Leeds-Bremen model 50 km: small diurnal variation of O 3, Ox constant Ozone O Ox

III/55 Diurnal variation of Ox species, 8°N, January 28, 2004 Model result from the modified Leeds-Bremen model 60 km: night: Ox = O 3 day: Ox  O Ozone O Ox

III/56 Diurnal variation of Ox species, 8°N, January 28, 2004 Model result from the modified Leeds-Bremen model 70 km: night: Ox = O 3 day: Ox = O Ozone O Ox

III/57 Diurnal variation of Ox species, 8°N, January 28, 2004 Model result from the modified Leeds-Bremen model 80 km: Ox  O Ozone O Ox

III/58 Brasseur and Solomon

III/59 Latitudinal distribution of O 3, Northern winter (January), ppm Model result from the modified Leeds-Bremen model Unrealistic high values in polar night (equilibrium model!)

III/60 Latitudinal distribution of O 3, Southern winter (July), ppm Model result from the modified Leeds-Bremen model Unrealistic high values in polar night (equilibrium model!)

III/61 Annual variation of O 3, Southern winter (July), ppm Model result from the modified Leeds-Bremen model tropics (0°N)

III/62 Annual variation of O 3, ppm Model result from the modified Leeds-Bremen model tropics (0°N) mid-lats (47°N)

III/63 Annual variation of O 3, ppm Model result from the modified Leeds-Bremen model tropics (0°N) mid-lats (47°N) polar (75°N)

III/64 Variation of ozone in latitude and season, measured by the TOMS satellite instrument for 1990

III/65 Variation of ozone in latitude and season, measured by the TOMS satellite instrument for 1990 Downward transport during polar winter Ozone hole (Antarctic winter)

III/66 Variation of total ozone related to the altitude of the tropopause and the 200 hPa level

III/67 Catalytic destruction of ozone First proposed by Bates and Nicolet, 1950, reactants: HOx

III/68 Catalytic destruction of ozone First proposed by Bates and Nicolet, 1950, reactants: HOx Molina and Rowland, 1974: Stratospheric sink for chlorofluoromethanes: Chlorine atom catalysed destruction of ozone Crutzen, 1970 th : Numerous studies about catalytic cycles of HOx and NOx

III/69

III/70 Catalytic destruction of ozone: usefull terms chain center Chain lengths N: number of times the cycle is executed before the chain center is destroyed  : rate of propagation (i.e., the rate of the slowest reaction involved, the rate- limiting step)  : rate of termination (rate of destruction of the chain center)

III/71 Catalytic destruction of ozone: usefull terms chain center Chain lengths N: number of times the cycle is executed before the chain center is destroyed Chain effectiveness  :