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V/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
V. The (tropical) tropopause
VI. Greenhouse gasses (GHG) and climate VII. Solar (decadal) variability and dynamical coupling
V/2
Climate: energy in the sun-earth system
Earth‘s radiation budget
Turco 1997
SW heatingUV/Vis/NIR
LW coolingThermal IR
V/3
solar and terrestrial radiation
Solar irradiance coming from the photospheric layer (Stefan-Boltzmann Law, Tsol=5800 K):
Radiative power (units: Watt) the solar photosphere:
Solar intensity at earth‘s radius:
4 8 72 4 2
5.67 10 5800 6.4 10sol sol
W WI T K
m K m
4 24sol sol solP T R
24sol
o
PI
r
24
2sol
o sol
RI T
r
„solar constant“6
695300
149.5 10
5800
sol
sol
R km
r km
T K
21386o
WI
m
V/4
solar and terrestrial radiation (II)
total solar intensity received on earth surface (R2 is only illuminated):
Mean radiative flux density on the entire earth surface:
radiation budget without atmospherenet radiative flux density (intensity) at surface
such a radiation budget can be set up at any altitude
2earth oP I R earth
2234344
earth oearth
P I WImR
F F F
F
F
V/5
Solar Insulation
2 6 245 / 45 10 /521 / 2
24 86400sec
MJ m J mW m
h
Wallace & Hobbs 2005
V/6
solar and terrestrial radiation
at earth‘s surface:
Radiative equilibrium at the surface (F=0)
4
4
4
o
osurface
IF
IF T a
thermal IR radiation emitted from surface
solar radiation (UV/VIS) reflectedback into space (a=0.3 planetary albedo)
40
14
0 (1 )4
1
4
surface
o
IF F F a T
IaT
02
84 2
3434
0.3
5.67 10
I Wm
a
WK m
255surfaceT K
F
F
V/7
Climate without atmosphere
without an atmosphere earth‘s mean surface temperature would be T=255K=-18°C. Atmosphere is responsible for thermal insulation and a global average surface temperature of T=288K=+15°C.
02
84 2
3434
0.3
5.67 10
I Wm
a
WK m
255surfaceT K
max( , 5800 ) / 265000 0.5B T K m
max( , 255 ) 10B T K m
solar radiation is a black body with T=5800Kattenuated by a factor of 265000 represents 99% of shortwave emission (<4m)
terrestrial radiation is a black body with T=255K and represents 99% of longwave emission (>4m)
shortwave and long wave spectrum on earth‘s surface
SW LW
V/8
SW and LW radiation from pole to pole
Wallace & Hobbs 2005
V/9
greenhouse gases: IR active gases
Hanel et al. 1972
V/10
simple climate model: the atmospheric green house effect
Simple model:
atmosphere is approximated as an infinitely thin layer having a temperature of TA. It is transparent to shortwave radiation (UV/vis) but opaque to longwave radiation (IR)
surface has a temperature of TB and reflects 30% (a=0.3) of shortwave radiation back into space (albedo=0.3). Like the atmosphere the surface is completely absorbing longwave radiation and acts like a blackbody with surface temperature TB.
4 4
4 4
4
2 0
1 04
1 04
in outA B AA A
in out oB A BB B
oA B A
F F F T T
IF F F a T T
IF F a T
14
14
14
1255
4
12 303
2
oA
oB A
a IT K
a IT T K
radiation budget (energy balance):
V/11
simple climate model: the green house effect
TA=255K corresponds to the mean temperature at 5.5 km altitude (~500 hPa). This altitude divides the real atmospheric mass in about two halves.
TB=303K=30°C is about 15°C larger than the global mean surface temperature of 288K.
The heating of the atmosphere occurs because of IR absorption of H2O, CO2, CH4 etc. However, in a real atmosphere:
Some of the IR region is transparent (atmospheric window) UV/vis region is not completely transparent mainly due to O3, O2,
and H2O absorption Clouds modify the planetary albedo (a=0.6-1.0)
Analogy to a real green house: glas is 60% transparent to UV/vis radiation but much less transparent
to IR heat-up of the glas house is mainly due to convection (wind
protection!). This is the major difference to the real atmosphere
V/12
atmospheric windows
atmospheric window(s)
greenhouse gases in IR atmospheric windows
Turco 1997
V/13
earth energy budget
Turco 1997
V/14
climate feedbacks: direct (radiation) and indirect
Stratospheric aerosols (major volcanic eruption): direct effect: changes in albedo (scattering/cooling) and absorption (soot/warming)Indirect effect: increases amount of CCN, more cloud can form
Role of clouds:Cloud cover changes modify planetary albedo
Turco 1997
Chemical feedbackOzone depletion contrbutes
to stratospheric coolingWarmer troposphere leads
to higher water vapor amounts, modifies clouds
Methane oxydation enhances stratospheric H2O (CH4+OHCH3+H2O), additional IR cooling
Chemical response to temperature changes
circulation changes (transport & chemistry)
V/15
stratospheric aerosol
V/16
Stratospheric aerosol and temperature
Impact of El-Chichon and Pinatubo increase in stratospheric temperatures in the tropics (increase of
2-3K @ 100hPa for about 1-2 years increase in H2O vapor (reduced freeze drying)?
anti-correlation between Arctic and tropical LS temperatureaerosol effect on Brewer-Dobson circulation
?
Dhomse et al., 2006
Pinatubo
El Chichon
V/17
Trends in greenhouse gases (surface): CO2
Note today:
[CO2] 382 ppmv
[CH4] 1800 ppbv
Mouna Loa Hawaii
Ahrens 1999
V/18
Trends in greenhouse gases (surface)
Note today:
[CO2] 370 ppmv
[CH4] 1800 ppbv
IPCC 2001
V/19
Current trends: CH4 and CO2
V/20
GHG in the past fromice cores
Note today:
[CO2] 370 ppmv
[CH4] 1700 ppbv
Age in kyears0 ky 150 ky
V/21
Surface temperature trend
Note: Year 2005 record warm year in NH NASA/GISS
V/22
radiative forcing: greenhouse gases
SROC IPCC
V/23
Forcing scenario (future prediction)
Turco 1997
V/24
Surface temperatures from the past to the future
change in NH surface temperature until 2100
from +1K to +5.5 K dependent on models
Mann et al, 1998
Mann et al., 1998: temperature proxy dataECHO-G1: climate model result
Cubash
V/25
GHG sources & sink
Major CH4 sink: CH4+OH CH3+H2O
CO2
CH4CFC
V/26
GHG space observation: local sources
Green house gases (CH4) and air pollution CO, SO2, NO2
Ric
hte
r
Buch
wit
z
V/27
Prediction of climate change
cooling
warming
Schmidt, MPI-HH
2xCO2 2xCO2 + GHG
V/28
Prediction of climate change
Temperature change from climate model due to doubling CO2 and changes in SST (sea surface temperature)
SST changes from a coupled ocean-atmosphere model with a 2xCO2 atmosphere
Schmidt, MPI-HH
Julydoubling CO2 only
SST change + doubling CO2
July
Changes in TChanging reaction rates
& heterogeneous chemistry
Changing atmospheric circulation (transport)
V/29
Ozone and climate change
stratospheric cooling leads to larger PSC volumes accumulated over winter
Update Rex et al. 2004, Rex et al. 2006
larger PSC volumes leads to higher observed heterogenous chemical ozone loss in Arctic winters
high variability due to transport & chemistry (BD circulation)
Arctic
Arctic
CTM model results (solid: 2.5° grid, light: 7.5° grid)
V/30
Current trends in GHG emissions
GWP: greenhouse gas warming potential (relative to CO2)
„success“ of Montreal protocol and amendments
„failure“ of Kyoto protocol
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