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