III/1 Atmospheric transport and chemistry lecture I.Introduction II.Fundamental concepts in atmospheric dynamics: Brewer-Dobson circulation and waves III.Radiative

III/1

Atmospheric transport and chemistry lecture

I. IntroductionII. Fundamental concepts in atmospheric dynamics:

Brewer-Dobson circulation and wavesIII. Radiative transfer, heating and vertical transport

IV. Stratospheric ozone chemistry

III/2

Processes affecting stratospheric O3

3/1997 3/1999

III/3


1. Basic concepts of atmospheric chemistry2. Ozone chemistry and ozone distribution3. Sources and distribution of ozone-related species4. Ozone trends5. The ozone hole6. Ion chemistry and solar variation7. Middle atmosphere processes: sprites, meteors, aurora

III/4


1. Basic concepts of atmospheric chemistry

III/5

What goes in ? What goes out ? horizontal / vertical transport

What goes on in there ?

gas-phase reactionssurface reactionsion 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 reactionssurface reactionsion 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

dDcCbBaA

reactants A and B form products C and Da,b,c,d: stoechiometric quantity of A, B, C, D

III/8


dDcCbBaA

Rate R of the reaction:

dtdD

ddtdC

cdtdB

bdtdA

aR 1111

rate of change of A

R: [molecules / cm3s]

III/9


dDcCbBaA


dtdD

ddtdC

cdtdB

bdtdA

aR 1111


BAkR k rate constant of the reaction[A] concentration (number density) of A[B] concentration of B

III/10


dDcCbBaA


dtdD

ddtdC

cdtdB

bdtdA

aR 1111


BAkadtdA

BAkR

rate of change of A

III/11

dDcCbBaA

BAkadtdA

rate constant k: from laboratory measurements

III/12

dDcCbBaA

BAkadtdA


An estimate of k from collision theory: molecules A and B are hard spheres of radii rA and rB

2

8

BAcollission

BA

BABoltzmannthermal

thermalcollission

rr

mmmmTk

v

vk

III/13

dDcCbBaA

BAkadtdA


An estimate of k from collision theory: molecules A and B are hard spheres of radii rA and rB

smoleccmk

Tk

vk thermalcollission

3

11

21

104

III/14

BACACBCBA *

activated complexreactants products

III/15

BACACBCBA *


E1: Activation energy

E2 energy gained by reactionH: reaction enthalpy

III/16

BACACBCBA *




The reaction takes place if the thermal energy of the reactants is larger than E1:k = A* exp(-E1/(kT))

Boltzmann factor

III/17

BACACBCBA *




The reaction takes place if the thermal energy of the reactants is larger than E1:k = A* exp(-E1/(kT))Arrhenius-form

III/18

Summary of gas-phase reactions

CBA First order (unimolecular) reactionphotolysis or thermal decomposition

EDBA Second order (bimolecular) reaction

DBA Three-body reaction

III/19


CBAMA * First order (unimolecular) reactionthermal decompositionpressure and temperature dependent

EDBA Second order (bimolecular) reactiontemperature dependent

DBA Three-body reaction

pressure

III/20


CBAMA * First order (unimolecular) reactionthermal decompositionpressure and temperature dependent

EDBA Second order (bimolecular) reactiontemperature dependent

DMD

DBA

*

* Three-body reactionpressure and temperature dependent

pressure

III/21

Photodissociation

ABJdtABd

BAhAB

AB

JAB: photolysis rate

III/22

quantum yield = 0: AB is not dissociatedquantum yield = 1: AB is totally dissociated

Photodissociation

number of photons absorbed

ABJdtABd

BAhAB

AB

JAB: photolysis rate

hFT

ddJ AB ,

quantum yield absorption cross section

actinic flux

III/23

First-order reaction

CBA

AkdtdA

A

III/24


CBA

tkAtA

AkdtdA

A

A

exp0

III/25


CBA

dtdAtkAtA

AkdtdA

A

A

exp0

Lifetime of A:

Ak1

III/26

Second-order reaction

DCBA

Lifetime of A:

BkAB

1

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 = kij[Ci][Cj] - kj[A][Cj] + Jj[Ci] – JA [A]

gas-phase productionand loss reactions of A

photolysis reactions forming and dissociationg A

III/28


2. Ozone chemistry and ozone distribution- Oxygen atmosphere- Ozone distribution- Catalytic cycles

III/29

Purely oxygen atmosphere (Chapmann cycle)

)(

2

12

323

323

232

22

rethermosphekMOMOOJOOhOkOOOkMOMOO

JOOhO

III/30

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

Mixing ratio

III/31


Mixing ratio

Ozone maximum

Second ozone maximum

III/32


Mixing ratio Number density

III/33



Maximum 30-40 km Maximum 20-30 km

III/34



Maximum 30-40 km Maximum 20-30 km The ozone colume (= total ozone) is dominated by the lower stratosphere

III/35

Purely oxygen atmosphere (Chapmann cycle)

)(2

)(2

2

)(

5231

421

4221

4221

*2

12

*3

123

323

323

232

12

22

slowkOODO

rethermosphekOODO

kOOODO

kNONDO

JODOhO

JDOOhO

JOOhOkOOOkMOMOO

rethermosphekMOMOOJOOhO

c

b

a

III/36

The Ox-family

Ox: reactive oxygenOx = O + O(1D) + O3

lifetime of family is long, family members transfer into each other in fast reactions

III/37

The Ox-family

Ox: reactive oxygenOx = O + O(1D) + O3

lifetime of family is long, family members transfer into each other in fast reactions

2131

5332*22 2222 OkODOkOOkOJJ

dtOd x

formation of Ox loss of Ox

III/38

Photochemical lifetimes of O3, O and Ox

compared to horizontal transport u

III/39



>40 km: Ox is dominated by transport40-80 km: Ox is dominated by chemistry>80 km: Ox is dominated by transport

III/40



>40 km: Ox is dominated by transport of ozone40-80 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




Chemical control from mid-stratosphere to mid-mesosphere

III/44




Chemical control from mid-stratosphere to mid-mesosphere

Transition zone of transport/chemistry control

III/45

The Ox-family: partitioning of family members

31

5

21

421

42*23

*3

1

33222

1

21

421

4332*222

31

53*333322

3

2

2

ODOk

ODOkNDOkOJOJdt

DOd

OOkOOkOk

ODOkNDOkOJOJOJdtOd

ODOkOJJOOkOOkdtOd

ba

ba

III/46

The Ox-family: partitioning of family members

31

5

21

421

42*23

*3

1

33222

1

21

421

4332*222

31

53*333322

3

2

2

ODOk

ODOkNDOkOJOJdt

DOd

OOkOOkOk

ODOkNDOkOJOJOJdtOd

ODOkOJJOOkOOkdtOd

ba

ba

from these equation the partitioning of family members can be calculated if photochemical equilibrium is assumed for O and O(1D), i.e,

0,01

dt

DOddtOd

III/47

The Ox-family: partitioning of family members from photochemical equilibrium

3322

3*3

3

2424

*3

3

1

OkOkJJ

OO

OkNkJ

ODO

ba

III/48

The Ox-family: partitioning of family members from photochemical equilibrium

3322

3*3

3

2424

*3

3

1

OkOkJJ

OO

OkNkJ

ODO

ba

both O and O(1D) are zero during night-time

in the stratosphere:[O3] >> [O] (Ox O3)

in the upper mesosphere:[O3] < [O] (Ox O)

III/49

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

(non-equilibrium model)

Noon

III/50


Noon< 50 km: Ox O3

> 70 km: Ox O50-70 km: transition zone, O and O3

O(1D) more than five orders of magnitude smaller

III/51


Noon Night

III/52


Noon Night

Ox O3 up to ~ 75 km

III/53

Diurnal variation of Ox species, 8°N, January 28, 2004Model result from the modified Leeds-Bremen model

40 km: no diurnal variation of ozone and Ox

OzoneOOx

III/54


50 km: small diurnal variation of O3, Ox constant

OzoneOOx

III/55


60 km: night: Ox = O3

day: Ox OOzoneOOx

III/56


70 km: night: Ox = O3

day: Ox = OOzoneOOx

III/57


80 km: Ox OOzoneOOx

III/58Brasseur and Solomon

III/59

Latitudinal distribution of O3, 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 O3, Southern winter (July), ppm Model result from the modified Leeds-Bremen

modelUnrealistic high values in polar night (equilibrium model!)

III/61

Annual variation of O3, Southern winter (July), ppm Model result from the modified Leeds-Bremen model

tropics (0°N)

III/62

Annual variation of O3, ppm Model result from the modified Leeds-Bremen model

tropics (0°N)

mid-lats (47°N)

III/63

Annual variation of O3, 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

23

2

23

2: OOOnet

OXOOXOOXOX

First proposed by Bates and Nicolet, 1950, reactants: HOx

III/68

Catalytic destruction of ozone

23

2

23

2: OOOnet

OXOOXOOXOX

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

III/69

III/70

Catalytic destruction of ozone: usefull terms

23

2

23

2: OOOnet

OXOOXOOXOX

chain center

Chain lengths N: number of times the cycle is executed before the chain center is destroyed

N

: 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

23

2

23

2: OOOnet

OXOOXOOXOX

chain center

Chain lengths N: number of times the cycle is executed before the chain center is destroyed

N

Chain effectiveness : N

Documents

III/1 Atmospheric transport and chemistry lecture I.Introduction II.Fundamental concepts in atmospheric dynamics: Brewer-Dobson circulation and waves III.Radiative