Physics and chemistry of the atmosphere
- brief overview on important effects -
 Basic properties of the atmosphere
 Greenhouse effect
 Stratospheric chemistry: ozone layer
 Tropospheric chemistry:
- winter smog
- summer smog
- oxidation capacity
Remote sensing of the atmosphere
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Basic properties of the atmosphere: composition
Remote sensing of the atmosphere
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Basic properties of the atmosphere: composition
Trace gases are important. They control:
-radiation absorption/emission
-energy supply for organisms
-chemical reactions
-energy transport (latent heat)
Remote sensing of the atmosphere
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FCKW
N2 O
CH4
CH3CCl3
CH3BR
CO
1Tag
trop. O 3
SO2
NOx
CH5 H 8
DMS
1hr
1s
CH5 H 8
CH3O
kurzlebig
100s
Lebensdauer
global
langlebig
mikro
moderat langlebig
Räumliche Skala
lokal
regional
1 Jahr
100 Jahre
Residence time of various
atmospheric trace gases
2
HO2
NO3
OH
10m
Remote sensing of the atmosphere
1km
100km
Transport Skala
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10000km
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Basic properties of the atmosphere: pressure profile
 g   ( z) 
dp ( z )
dz
Hydrostatic
equation
p(z+dz)
z + dz
p(z)
z
Remote sensing of the atmosphere
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Basic properties of the atmosphere: pressure profile
 g   ( z) 
dp ( z )
dz
Hydrostatic
equation
p(z+dz)
z + dz
With ideal
gas law
pV  N ART
it follows:
N A M
Mp


RT
V
p(z)
z
and:
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For isothermal atmosphere (t=const):
p ( z )  p (0)  e

Mg
z
RT
RT
 z0
Mg
Scale height z0:
p( z )  p(0)  e

z
z0
Remote sensing of the atmosphere
 8km
=> Scale height is different
for different molecules
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Basic properties of the atmosphere: temperature profile
120
1E-4
1E-3
Thermosphäre
1E-2
Mesopause
100
1E-1
Mesosphäre
60
Stratopause
1E+0
Höhe [km]
Druck [mb]
80
40
1E+1
Stratosphäre
Ozonschicht
1E+2
20
Tropopause
Troposphäre
1E+3
-100
0
-50
0
50
Temperatur [°C]
Remote sensing of the atmosphere
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The temperature profile in the troposphere is controlled by convective
circulation. The energy originates from the warm surface which is heated by
solar irradiation.
For the calculation of the temperature change with altitude it is assumed that
the air parcels move adiabatically. That means they don’t exchange energy
with their environment. This assumption is justified by comparison with the
rates of radiative cooling with the transport times within the tropopause.
When an air parcel ascends it expands and thus does work against the air
pressure.
The first thermodynamical law is:
(U = internal energy, Q = obtained heat, W = work done to the gas, p =
pressure, V = volume)
For an ideal gas the internal energy only depends on the temperature T it is:
It follows:
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With ideal gas law:
or
It follows:
With Cp = specific heat at constant pressure, Cp + R = Cv
With
It follows:
For adiabatic processes: dQ = 0 and we get:
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With barometric height formula:
It follows:
And we get the dry adiabatic temperature gradient:
Values for air:
Moist adiabatic temperature gradient:
If air ascends and cools, it will eventually reach the temperature at which water vapor
condenses. The condensation process releases latent heat which provides energy to the air
parcel. Thus, the temperature decrease with height is smaller than for the dry adiabatic
temperature gradient.
The typical temparture gradient in the lower atmospere (up to about 10km) is determined
by the moist adiabatic temperature gradient. Typical values are 0.6K/100m
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Long time it was known (e.g. from mountain climbing) that the temperature decreases
with height. It was also assumed that the temperature decrease would continue until the
‚upper edge‘ of the atmosphere.
About more than 100 years ago, several important observations were made, which
showed that the actual temperature gradient differs from this expectation:
 1880 - 1908: Discovery of the ozone absorption (especially in the UV)
 1902: Balloon borne temperature measurements (Teisserenc de Bort and Richard
Assmann) showed a temperature increase at about 11km.
 1913: Balloon borne observations (Wigand) of the ozone absorption show no
significant increase of the UV intensity up to 10km
 1926: Umkehr-Effekt (Paul Götz): Maximum of the ozone layer at about 25km
Remote sensing of the atmosphere
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Basic properties of the atmosphere: temperature profile
120
1E-4
1E-3
Thermosphäre
1E-2
Mesopause
100
1E-1
Mesosphäre
60
Stratopause
1E+0
Höhe [km]
Druck [mb]
80
40
1E+1
Stratosphäre
Ozonschicht
1E+2
20
Tropopause
Troposphäre
1E+3
-100
0
-50
0
50
Temperatur [°C]
Remote sensing of the atmosphere
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Greenhouse effect
© W. Roedel
The solar irradiation is S = 1368 W/m² (Solarkonstante). The earth cuts a cross
section of r² off the solar beam. It reflects a fraction A (albedo) back into space.
The absorbed power (1-A)Sr² has to be compensated by the terrestrial IR
radiation to avoid a heating of the earth. From the Stefan-Boltzmann-law it follows
that the terrestrial radiation is T4 · 4r²
It follows: Taverage = -18°C
but
Treal = +15°C
Remote sensing of the atmosphere
Greenhouse effect T = +33°C
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+50°
a) A roof of
normal glass
+40°
b) A roof of
rock salt
+25°
c) No roof
Some considerations to the ‚greenhouse effect‘
a) A roof of normal glass is transparent for solar radiation, but opaque for
IR radiation.
b) A roof of rock salt is transparent for solar and IR radiation
c) No roof
To which model does the atmosphere fit?
Remote sensing of the atmosphere
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Atmospheric radiation budget
Remote sensing of the atmosphere
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63.5%
Contribution of different
greenhouse gases to the
natural greenhouse effect
(IPCC, 1995)
22.5%
7.2%
Remote sensing of the atmosphere
4.2%
2.7%
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2
1
0
-1
(C) ICCP
Remote sensing of the atmosphere
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Summe Antropogen
Solare Einstrahlung
Aerosol indirect
(Wolken)
Aerosol direkt
Albedo
(Schneeoberfläche)
Albedo
(Landnutzung)
trop. O3
strat. O3
strat. H2O aus CH4
künstlich
natürlich
gesamt künstlich
FCKW
N2O
CH4
-2
CO2
Stärke des Klimaantriebs [W/m²]
Stärke verschiedener Klimaantriebe (Radiative Forcing, Differenz zur Zeit vor
der Industrialisierung).
Rükkopplungen verstärken oder dämpfen ursprüngliche Klimaeinflüsse
Ohne Rückkopplungen
Störung der Klimabilanz, z.B.
doppelte CO2 Konzentration
3.7 W/m2
T = 1.2°C
Klimasystem
Mit Rückkopplungen
Verstärkung der Störung
durch Rückkopplungen
3.7 W/m2
Klimasystem
+1.9 W/m2
+0.3 W/m2
+1.6 W/m2
Wasserdampf
Albedo
Wolken
bis -0.2 W/m2
T = 1.5°C - 5.5°C
Rückkopplungen
Störung der Klimabilanz, z.B.
doppelte CO2 Konzentration
-0.8 W/m2 TemperaturGradient
Remote sensing of the atmosphere
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Report of the
Intergovernmental
Panel of Climate
Change (IPCC),
http://www.ipcc.ch/
Remote sensing of the atmosphere
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Millionen km2
0.4
0.2
0
Jahresmittel
10-Jahresmittel
-0.2
-0.4
-0.6
Anomalie des arktischen See-Eises
-0.8
1980
1985
1990
1995
2000
2005
Jahr
Millionen km2
0.4
Anomalie des antarktischen See-Eises
0.2
0
-0.2
-0.4
Jahresmittel
10-Jahresmittel
-0.6
-0.8
1980
1985
1990
1995
2000
2005
Jahr
Von Satelliten gemessene Ausdehnung des See-Eises in beiden Hemisphären
während der letzten 30 Jahre. Dargestellt sind die Abweichungen vom
Mittelwert 1979 – 2005 (Daten aus Comiso, 2003 und Lemke et al., 2007).
Remote sensing of the atmosphere
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Remote sensing of the atmosphere
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Remote sensing of the atmosphere
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Global circulation patterns redistribute energy
Why not
at the
equator?
Average near surface temperature as function of latitude
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Global circulation patterns redistribute energy
Remote sensing of the atmosphere
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Complex atmospheric
circulation patterns
Convection
-heat gradient
-gravitation
cold
Solar irradiance
hot
cold
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CFC + h 
-> Cl
+ O 1D
summer
op
p
Tro
se
u
a
winter
rapid mixing
Schematic diagram of the Brewer-Dobson Circulation (adapted from
Solomon et al. [1998]). Because the stratosphere contains only about
10% of the total atmosphere, the circulation must turn over many times
to destroy all of the CFCs present, resulting in a long atmospheric live
time of these species.
Remote sensing of the atmosphere
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Ozone in the stratosphere
Chapman Cycle [1930].
O2 + h

2O
O + O2 + M

O3 + M
O3 + h

O2 + O(1D)
O(1D) + M

O+M
O3 + h

O + O2
O + O +M

O2 + M
O + O3

2 O2
Remote sensing of the atmosphere
(  240nm)
(  320nm)
Odd oxygen is
produced
Odd oxygen is
conserved
(  1180nm)
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Odd oxygen is
destroyed
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40
Height [km]
measurements
30
Chapman-cycle
20
10
0
5
10
15
20
Ozone mixing ratio [ppm]
Comparison of measured ozone profiles and modelled ones taking into
account only the reactions of the Chapman-cycle (adapted from Röth
[1994]).
Remote sensing of the atmosphere
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Additional (catalytic) Ozone destruction mechanisms:
Net:
X + O3

XO + O2
XO + O

X + O2
O + O3

2O2
with:
X = OH, NO, Cl, Br
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Until the mid 1990s the stratospheric Clorine load increased
units:
1012 g Cl yr-1
Stratospheric
Chlorine compounds
accumulation: 0.08
0.03
0.19 Precipitation
0.24
Organic chlorine
(mostly CH3Cl)
Oceanic
emissions
2.5
Precipitation,
HO-reaction
5
CFCs
Tropospheric
accum.: 0.56
1
600
Chloride ion
in sea salt
aerosol
0.8
3
1.5
Biomass
burning
Inorganic chlorine
compounds
(mostly HCl)
Precipitation HCl
610
7
Industrial
emissions
Volcanoes
Wave
generation
6000
Sedimentation,
Precipation
5400
Global atmospheric chlorine cycle
(adapted from Graedel and Crutzen [1993]).
Remote sensing of the atmosphere
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[ppt]
300
200
global averaged
CFC-11 mixing ratios
100
76
78
80
82
84
86
88
90
92
94
year
Global averaged increase of CFC11 (adapted from IPCC [1996]).
Altitude profiles of CFC-11 (bottom) and
CFC-12 (top) [NASA, 1994].
Remote sensing of the atmosphere
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Ozone hole, Antarctica
1. März 1979
1. Nov. 1979
100
1. März 2007
1. Nov. 2007
300
400
500
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Remote sensing of the atmosphere
Ozongesamtsäule
aus
Satellitenmessungen über
dem Nord- und Südpol im
polaren Frühling 1979
und 2007. (Daten vom
NASA Goddard Space
Flight
Center,
http://toms.gsfc.nasa.gov/i
ndex_v8.html)
200
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Ozone hole, Antarctica
25
Ozonprofile am
Südpol
Oktobermittelwerte
1967 - 1971:
282 DU
300
Hoehe [km]
Ozon Gesamtsaeule [DU]
350
250
200
20
15
7. Oktober 1986:
158 DU
150
100
1950
1960
1970
1980
Zeit
1990
2000
8. Oktober 1997:
112 DU
2010
10
Ground based measurements,
Halley, Antarctis
Farman et al. 1985; Johnes et al.,
1995 und SPARC, 2009
Remote sensing of the atmosphere
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0
5
10
15
20
Ozon Partialdruck [mPa]
(from Hoffmann et al., 1997)
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....what has been ignored before:
Polar Stratospheric Clouds over Kiruna (Sweden), ©Carl-Fredrik Enell.
Remote sensing of the atmosphere
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Dynamical and photochemical development in the
stratosphere during polar winter
Gas phase
reactions
Abundance
Surface
reactions
ClO + 2 Cl2O2
ClONO2
HCl
Fall
Early winter
Denitrification
Dehydration
Transport
CFC 
Late winter
Spring
End of polar night
photochemical ozone destruction
hv (UV)
Stratosphere 
Remote sensing of the atmosphere
Time
PSC
Reservoir compounds
(HCl, ClONO2)
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BrO
 active comp.  OClO
(Cl, ClO)
Ozone destruction
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Catalytic ozone destruction cycle through chlorine
Quadratic
dependence
on ClO
Dependence
on sun light
Net:
Remote sensing of the atmosphere
2(Cl + O3

ClO + O2)
ClO + ClO + M

Cl2O2 + M
Cl2O2 + h

Cl + ClOO
ClOO + M

Cl + O2 +M

3O2
2O3
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Temperature differences between both hemispheres
Envelope of minimum temperature 1980-1988 at about 90
mb from MSU measurements [WMO 1991].
Remote sensing of the atmosphere
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Predicted future
atmospheric burden of
chlorine (adapted from
Brasseur [1995]).
Remote sensing of the atmosphere
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6
35°N - 60°N
0
-3
-6
-9
0
-3
-6
-9
-12
-12
-15
-15
1970
1980
1990
35°S - 60°S
3
Abweichung [%]
3
Abweichung [%]
6
2000
1970
1980
1990
2000
Zeit
Zeit
Aus Messungen von Bodenstationen gewonnene Zeitserien der atmosphärischen
Ozongesamtsäule in mittleren Breiten. (nach WMO 2006).
Remote sensing of the atmosphere
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Questions:
• When will ozone hole close?
(influence of climate change)
• How important are bromine compounds?
• Will there be an ozone hole over the Arctic?
• How strong does ozone change in mid-latiudes?
Remote sensing of the atmosphere
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’London Smog’ (John Evelyn, Fumifugium, 17th century)
‘It is this horried smoake which obscures our church and makes our places look old, which
fouls our cloth and corrupts the waters, so as the very rain, and refreshing dews which fall
in the several seasons, precipate to impure vapour, which, with its black and tenacious
quality, spots and contaminates whatever is exposed to it.
But without the use of calculations it is evident to every one who looks on the yearly bill
of mortality, that near half of the children that are born and bred in London die under two
years of age. Some have attributed this amazing destruction to luxury and the abuse of
spirituos liquors: these, no doubts, are powerful assistants; but the constant and
unremitting poison is communicated by the foul air, which, as the town still grows larger,
has made regular and steady avances in its fatal influence.’
‘Es ist dieser schreckliche Rauch, der unsere Kirchen verdunkelt und unsere Paläste alt aussehen
läßt; der unsere Kleider verdreckt und unser Wasser verdirbt. Insbesondere den Regen und den
erfrischenden Tau, die sich zu unreinem Dunst niederschlagen, der schwarz und zäh alles benetzt, das
ihm ausgesetzt ist.
Aber ohne zu rechnen ist es auch für jeden offensichtlich, der in die Jährliche Todesstatistik liest, daß
fast die Hälfte der in London geborenen Kinder im Alter von nicht einmal zwei Jahren stirbt. Manche
glauben daß diese erschreckende Entwicklung auf Luxus und Mißbrauch von alkoholischen
Getränken zurückzuführen sei. Diese Faktoren mögen die Entwicklung sicherlich begünstigen, aber
das wahre Gift erreicht uns durch die verdorbene Luft, die, solange die Stadt stetig wächst, ihren
verderblichen Einfluß beständig erhöht.
Remote sensing of the atmosphere
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’London Smog’ (also wintersmog, sulfur smog)
• In the 13th century coal (with high sulfur content) began to replace wood for
domestic heating and industrial use in London
• Earliest massive human impact on the atmosphere
• The effects of smog on human health were evident, particularly when smog
persisted for several days. Many people suffered respiratory problems and
increased deaths were recorded, notably those relating to bronchial causes.
• The first smog-related deaths were recorded in London in 1873, when it killed
500 people. In 1880, the toll was 2000. London had one of its worst experiences
with smog in December 1892. It lasted for three days and resulted in about 1000
deaths.
• London became quite notorious for its smog. By the end of the 19th century,
many people visited London to see the fog.
• Despite gradual improvements in air quality during the 20th century, another
major smog occurred in London in December 1952. The Great London Smog
lasted for five days and resulted in about 4000 more deaths than usual.
Remote sensing of the atmosphere
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The London smog disaster of 1952. Death rate
with concentrations of smoke
Hazardous driving conditions due to smog
(see also http://www.met-office.gov.uk/education/historic/smog.html)
Remote sensing of the atmosphere
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Environmental damage due to sulfur emissions
 Anthropogenic sulfur emissions were in particular responsible for
the first non-local pollution
 At the end of the 1960s in Scandinavia a massive fish-dying
occurred in inland waters. It was found out that the reason was an
acidification of the soil. Finally it turned out that it was caused by
strong industrial SO2 emissions from Great Britain.
 The Waldsterben was also mainly caused by SO2 emissions
 Since the mid of the 1980s the SO2 -emissions were strongly
reduced due to effective filter techniques.
 Today very strong smog events in China
Remote sensing of the atmosphere
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SO2 reacts rapidly with OH to form HSO3 (1), which reacts with O2 to form SO3
(2). It is soluble in clouds and aerosols, where it reacts with H2O2. As a result
of these processes, SO2 is converted to H2SO4 (3), consequently causing Acid
rain and deforestation. In general the maximum concentration of SO2 is close
to its source and the amount of SO2 decreases rapidly as the distance from the
source increases, indicating a short tropospheric lifetime of typically a few
days.
SO2
+ OH
HSO3 + O2
SO3
+ H2 O2
M


M

HSO3
(1)
SO3 + HO2
(2)
H2SO4
(3)
In the dry stratosphere, particularly in the lower stratosphere where the
concentration of OH is relatively small, the lifetime of SO2 is longer than in the
troposphere being of the order of several weeks.
Remote sensing of the atmosphere
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Typical conditions for winter smog:
-primary pollution:
SO2, soot particles
-secundary pollution :
H2SO4, Aerosols
-Temperature:
2°C
-Relative humidity:
high, typically foggy
-kind of inversion:
ground inversion
-time of maximum pollution:
early morning
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Los Angeles Smog
(Sommersmog, Ozonsmog)
• Ozone affects health
• Ozone damages plants
• Ozone destroys material
• Ozone determines the
oxidation capacity of the
atmosphere
Remote sensing of the atmosphere
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Impact of
Ozone on
Rubber
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Ozone production in the troposphere, summer smog
Penetration depth of UV radiation
-In the troposphere, not
enough UV radiation is
available for ozone
formation through O2
photolysis
-where does tropospheric
O3 originate from?
DeMore et al., 1997
Remote sensing of the atmosphere
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Early assumption
Stratosphere
Troposphere
Todays knowledge
Stratosphere
Troposphere
Remote sensing of the atmosphere
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Ozonsmog
(Los Angeles, 1940s, Haagen-Smit, 1952)
Radical chemistry, Ozone production in the troposphere:
RO2 + NO

RO + NO2
NO2 + h

NO + O (  410nm)
O + O2 + M

O3 + M
The occurance of ozone smog depends on the concentrations
of volatile organic compounds (VOC) an nitrogen dioxid
(NO2)
Without pollution, ozone is produced by oxidation of CH4 and
CO => tropospheric background ozone
Remote sensing of the atmosphere
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NOx limited
VOC limited
A VOC to NOx ratio of 8 to 1 is often cited as an approximate decision point for determining the relative
benefits of NOx vs. VOC controls. At low VOC to NOx ratios (< about 4 to 1), an area is considered to be
VOC-limited; VOC reductions will be most effective in reducing ozone, and NOx controls may lead to ozone
increases. At high VOC to NOx ratios (>about 15 to 1), an area is considered NOx limited, and VOC controls
may be ineffective. When VOC to NOx ratios are at intermediate levels (4 to 15), a combination of VOC and
NOx reductions may be warranted.
Remote sensing of the atmosphere
[email protected]
http://www.mpch-mainz.mpg.de/satellite
Importance of ‚local‘ effects?
Average concentrations of NO2 in Germany
Emissions of NMHC in Germany
Days with
[O3] > 240 ug/m³
in Germany
Remote sensing of the atmosphere
[email protected]
http://www.mpch-mainz.mpg.de/satellite
What about tropospheric background ozone concentrations?
Average O3 concentration
(Germany, all stations, (c) Umweltbundesamt)
48
46
44
42
[ug/m³]
Montsouris
Cape
Arcona
40
38
36
34
32
30
1975
1980
1985
1990
1995
2000
Year
Increase of background
ozone in Europe
(Volz and Kley, 1988)
Remote sensing of the atmosphere
[email protected]
http://www.mpch-mainz.mpg.de/satellite
CO and CH4 column
above the
Jungfraujoch station
1985 - 1996
Mahieu et al., 1997
Remote sensing of the atmosphere
[email protected]
http://www.mpch-mainz.mpg.de/satellite
Discovery of the ‘Cleansing agent’ of the atmosphere (OH-radical, Levi, 1971)
O3 + h

O(1D) + O2
O(1D) + H2O

2OH•
(  310nm)
OH• ist a (free) radical. Radicals are molecule fragments with unpaired electrons. Thus their
bound conditions are not required and they are very reactive. The production of radicals depends
on the fission of molecules and requires high energy. Typically, this energy is supplied by
photons. Radicals are the ‘active players’ of photochemistry.
OH reacts with almost all atmospheric trace gases which is the prerequisite for their destruction.
This ability to destroy atmospheric trace gases is called oxidation capacity.
OH is very reactive (within seconds). Although its concentrations are very low, it is the most
important atmospheric reactand.
OH exists only during day. Will concentrations of atmospheric pollutants increase during
night?
Remote sensing of the atmosphere
[email protected]
http://www.mpch-mainz.mpg.de/satellite