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Module “Atmosphere”Introduction and Basics
Dr. Axel KleidonMax-Planck-Institut für Biogeochemie
Day 1
29.02.20161
IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
Motivation for this CourseGoal: provide the basic background of climate physics to
understand biogeochemical cycling within the Earth system
2
Field et al. (1998) Science
Patterns of net primary productivity reflect limitations imposed by climate
gC m -2 yr-1
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IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
Overview of the Module
Date Topic Lecturer
29.02. Introduction and Basics Kleidon
07.03. Radiation Feist, Marshall
14.03. Dynamics Gerbig, Rödenbeck
21.03. Land Surface Exchange Gerbig, Kolle
22.03. Feedbacks and Change Kleidon, Heimann
Structure:
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IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
About myself
4
Dr. Axel Kleidon
e-mail: akleidon@bgc-jena.mpg.deoffice: A2.015 (BSYS)phone: 57-6217background: M.Sc. (physics), Ph.D. (meteorology)at MPI-BGC: group leader “Biospheric Theory and Modelling” (since 2006)scientific interests: atmosphere-biosphere interaction, vegetation modelling, thermodynamics of the Earth system, Gaia hypothesis
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IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
About yourself
• What is your name?
• What is your background in atmospheric/climate science?
• What are your expectations for this course?
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IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
Literature
66
IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
Overview of Today
Time Topic09:00 Overview of the module09:00
1. Introduction to the climate systemShort break2. Physical principles3. Atmospheric structure
12:30 Lunch break14:00 4. Radiation14:00
5. Global energy balanceShort break6. Atmospheric dynamics7. Biogeochemical cycles
17:00 End
7
Ewith several simple exercises, marked by on the slides
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IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
1. Introduction
-180 -120 -60 0 60 120 180
-90
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60
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-30 -20 -10 0 10 20 30Annual Mean Temperature (°C)
-180 -120 -60 0 60 120 180
-90
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-30
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30
60
90
0 500 1000 1500 2000Annual Precipitation (mm)
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-30
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30
60
90
0 100 200 300 400Net Solar TOA (W/m2)
Forcing:solar radiation
8
Predictable mean variations in
physical variables
Temperature
Precipitation
Net solar radiation at the Top Of the Atmosphere (TOA)
(includes effects of clouds and ice)
Climatesystem
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IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
Dominant time periods associated with temperature variations, most are caused by external forcing, but amplified by internal dynamics
Introduction
Peixoto and Oort: Physics of Climate
9
Diurnal scale(day/night)
Annual scale(seasons)Orbital variations
(ice ages)
Synoptic scale(weather)
9
IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
To understand climate, we need to understand the physical relation-ships between solar forcing, internal dynamics, and observable variables
Introduction
SolarForcing
Climate systeminternal dynamics:
transport and conversions
Characteristicpatterns
Observations(temperature,precipitation)
Physicallaws
10
Biogeochemicalcycles
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IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
The climate system consists of the atmosphere (gaseous), oceans (liquid), land (mixed), cryosphere (solid water) and lithosphere (solid)
The Climate System
11
Atmosphere
Ocean Land
Cryo-sphere
Lithosphere
Water
Surface area of 511 1012 m271% 29%
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IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
Water on Earth
Relevance to climate: • affects radiative transfer (reflectivity by clouds, snow; greenhouse effect)• transports large quantities of energy
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Water reservoir % stateOceans 97,0000% liquidIce caps and glaciers 2,2000% solidGroundwater 0,7000% liquidLakes and streams 0,0130% liquidSoil moisture 0,0130% liquidAtmosphere 0,0009% gaseous
Hartmann, Table 1.2
Uneven distribution of water:
Solidfixed volume,fixed shape
Liquidfixed volume,
free shape
Vaporfree volume,free shape
2.5 MJ/kg
0.3 MJ/kg
2.8 MJ/kg
Phase transitions and energy:
requires heatreleases heat
Ocean 7%Snow 35-90%Clouds 20-70%
Hartmann, Tables 3.2 and 4.2
Reflectivity of water:
E
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IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
Internal dynamics are ultimately driven by differences in radiative exchange with space and coupled by energy and mass fluxes
The Climate System
Atmosphere
Ocean Land
Cryo-sphere
13
Solar radiation
Lithosphere
Terrestrial radiation
Driver: differences in solar radiationRelevance: distribution and conversions of heat and mass
Driver: wind, differences in densityRelevance: heat storage, distribution of heat and mass, evaporation
Driver: radiative heating, windRelevance: heat storage, vertical exchange of heat and mass
342 W m-2 102 W m-2 240 W m-2
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IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
Atmosphere: Composition
Constituent m-w conc. Total mass (g)Nitrogen N2 28 78% 3.9 1021
Oxygen O2 32 21% 1.2 1021
Argon Ar 40 1% 6.6 1019
Water vapor H2O 18 variable 1.7 1019
Carbon dioxide CO2 44 353 ppmv 2.8 1018
Neon Ne 20 18.2 ppmv 6.5 1016
Krypton Kr 84 1.14 ppmv 1.7 1016
Helium He 4 5.24 ppmv 3.7 1015
Methane CH4 16 1.72 ppmv 4.9 1015
Xenon Xe 131 87 ppbv 2.0 1015
Ozone O3 48 variable 3.3 1015
Nitrous oxide N2O 44 310 ppbv 2.3 1015
Carbon monoxide CO 28 120 ppbv 5.9 1014
Hydrogen H2 2 500 ppbv 1.8 1014
Ammonia NH3 17 100 ppbv 3.0 1013
Nitrogen dioxide NO2 46 1 ppbv 8.1 1012
CFC-11 CCl2F2 121 480 pptv 1.0 1013
…
based on Hartmann, Table 1.1
14
• > 99% of the atmosphere consists of inert gases (they do not react without addition of energy)• Gases of particular importance:
• Greenhouse gases (absorb terrestrial radiation), e.g. H2O, CO2, CH4, N2O, CO
• UV absorption: oxygen (O2 and O3, largely of biotic origin, reactive)
• Atmospheric chemistry (e.g., CFC-11; CFC-12 are man-made compounds that affect ozone chemistry)
• Water vapor: highly variable • Also: droplets, aerosols
m-w: molar weight, conc.: volume concentration
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IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
Atmosphere: Temperature
Hartmann, Figure 1.2
• The atmosphere shows a typical vertical profile of temperature• The lapse rate describes the rate of decrease in temperature with height• Distinct layers defined by a sign change of lapse rate• Inversions describe areas in which temperature increase with height• Radiative and convective processes shape this profile• Most climate-relevant dynamics take place in the lowest layer (troposphere)
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IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
Hartmann, Figure 1.8
Atmosphere: Pressure
• Pressure defined as force per unit area in units of hPa
• Air pressure typically decreases nearly exponentially with height• Total pressure is composed of sum of partial pressures of different compounds• Partial pressure of water vapor decreases much faster with height
16
p =F
A=
mg
A
p! pressurem! massF! force
A! areag! = 9.81 m s-2
E
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IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
Ability of air to hold moisture is restricted up to its saturation vapor pressure, esat, which depends strongly on temperature T.
Atmosphere: Water vapor
17
0
2000
4000
−20 −10 0 10 20 30
Air Temperature (°C)
Satu
ratio
n pr
essu
re (P
a)
T: Temperature in Kelvinesat: partial pressure in Pa
Saturation increases by about 6.5%/K at global mean temperature of
15°C
esat = 611 · e19.83�5417/T
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IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
Oceans: Composition
Component g/kg
Chloride 19,353Sodium 10,760
Sulfate 2,712Magnesium 1,294Calcium 0,413
Potassium 0,387Bicarbonate 0,142Bromide 0,067
Strontium 0,008Boron 0,004
Fluoride 0,001
Hartmann Table 1.3
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Mean Compositionof Sea Water
Spatial deviations of mean salinity (35 g/kg)
• Relevance: salinity affects density of sea water (and thereby buoyancy, thermohaline circulation)• Driver: mostly the hydrologic cycle
http://www.nodc.noaa.gov/OC5/
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IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
Oceans: Structure
Hartmann, Figure 1.10
Mixed layer
19
Thermocline
Deep ocean
The vertical temperature profile can typically be partitioned into three regions:• Mixed layer: top 20-200m, well mixed, exchanges with atmosphere• Thermocline: rapid change in temperature• Deep ocean: below thermocline
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IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
Cryosphere
Reservoir Volume (km3) %Antarctic Ice Sheet 30.1 106 89,3 %Greenland Ice Sheet 2.6 106 8,6 %Mountain Glaciers 0.3 106 0,8 %Permafrost 0.2-0.5 106 1,0 %Seasonal snow 2-3 103 Sea Ice 4-10 104
• Mostly in polar regions• > 10% of Earth’s surface (3% ice sheets, 7% sea ice)• Highly reflective surface (reflection of 60% and more)• Stores freshwater• Affects ocean salinity, sea level• Forms topography
20
NASA/Goddard Space Flight Center E
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IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
Land
• 29% of Earth’s surface• Surface properties are strongly affected by vegetation
• reflectance (e.g., Sahara: 35%, rainforest 14%)• ability to evaporate (stomatal conductance, rooting depth)
• Topography affects precipitation, heating, and flow• relevant to humans:
• 10-13% farming and settlements• 20-25% grazing lands
180˚ 270˚ 0˚ 90˚ 180˚-90˚ -90˚
-60˚ -60˚
-30˚ -30˚
0˚ 0˚
30˚ 30˚
60˚ 60˚
90˚ 90˚
-10000 -7500 -5000 -2500 0 2500 5000 7500 10000
height (m)
180˚ 270˚ 0˚ 90˚ 180˚-90˚ -90˚
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30˚ 30˚
60˚ 60˚
90˚ 90˚
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height (m)
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IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
2. Physical Principles
1. Conservation laws: Some basic physical quantities are conserved. This results in balance equations which account for the changes of content with the difference of in- and outfluxes
• energy
• mass
• momentum
• [angular momentum, charge, ...]2. Thermodynamics: Conversions of energy, mass and momentum are associated with energy conversions. Thermodynamics sets the rules:
• energy is conserved during conversion process
• energy is dispersed (increase of entropy) => sets direction
• sets limits to the magnitude of energy conversions22
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IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
Balance Equations
• Energy balances describe changes in heat storage in relation to heat fluxes and predict changes in temperature
• Example: surface energy balance on land
• Specific heat capacity cp and density ρ determine how fast temperature changes as a result of heat fluxes.
23
E
cp⇢dTs
dt= Rs �Rl �H � �E �G
change in heat storage
radiativefluxes
sensible andlatent heat fluxes
groundheat flux
23
IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
Balance Equations
• Simplest representation of the mass balance is the linear reservoir
• Steady-state represents the case in which contents do not change in time (dW/dt = 0). In this case, contents are given by:
• Other example: diffusion equation
24
ContentsW
InfluxJin
OutfluxJout
dW
dt= Jin � W
�
• outflux assumed to be proportional to contents W with a residence time τ
Wss = Jin �
change incontents
sum offluxes
24
IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
Thermodynamics
There are a total of four laws of thermodynamics. The first and second law are the most important for calculations.
• First law states energy conservation, with heat exchanged dQ being balancedby internal changes dU and work performed in time:
• For heat fluxes through time, it canbe expressed as:
• can be generalized to all forms of energy conversions
25
heatcontent
U
heat fluxJin
heat fluxJout
powerP
dU = dQ� dW
cp
⇢dT
dt=
dU
dt= (J
in
� Jout
)� P
25
IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
heatcontent
U
heat fluxJin
heat fluxJout
Thermodynamics
• The second law describes the direction of increased energy dispersal among energy conversion processes. It requires the entropy S during a conversion process to increase (or stay unchanged)
• Typically, this is evaluated in the contextof an entropy balance of the system:
26
powerP
dS � 0Tin
Tout
dS
dt= � +
Jin
Tin
� Jout
Tout
entropy producedby processes
within the system(σ ≥ 0)
entropy exchangeof the system
change ofentropy ofthe system
26
IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
Thermodynamics
27
Externalheating
Externalcooling
System A(isolated)
Steady state
Redistributionof heat
Initial stateTime
System B(non-isolated)
Thermodynamic equilibrium
Thermodynamic disequilibrium
Redistributionof heat
Redistributionof heat
Hot Cold
Hot Cold Externalheating
Externalcooling
Warm Cool
Warm Warm
Example
Cup of cold coffee
Pot ofboiling water
Examples of how the Second Law sets the direction(in general: fluxes deplete their driving gradient)
27
IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
Thermodynamics
Atmospheric dynamics: generation of kinetic energy and frictional dissipation affect wind speeds
• generation of kinetic energy out of heating differences (surface-atmosphere, tropical-polar)
• dissipation of kinetic energy due to friction
Biotic activity: photosynthesis and respiration alter biomass
• “endotherm”: ! CO2 + H2O + light → CH2O + O2
• exotherm:! ! CH2O → CO2 + H2O + heat
solar radiation heatchemical energy
28
heating difference heatkinetic energy
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IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
heatcontent
U
heat fluxJin
heat fluxJout
Thermodynamics
• Both laws combined set the Carnot limit on energy conversions in steady state. It represents the idealized upper limit on energy conversion that fulfills the second law when
• Then, the two laws take this form:
29
powerP
Tin
Tout
� = 0
Jin
Tin
� Jout
Tout
= 0
Jin
� Jout
� P = 0first law:
second law:
Carnot limit: P = Jin
Tin
� Tout
Tin
⌘ =Tin
� Tout
Tin
Carnot efficiency:
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IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
Thermodynamics
30
Heat fluxWarm temperature, low entropy
Power = work/timeNo entropy
Waste heat fluxCold temperature, high entropy
Trade-off between power and waste heat flux affects
entropy exchange of the system
a. Steam engine b. Atmospheric heat engine
Surface
Absorption of solar radiation Warm temperature, low entropy
Emission of terrestrial radiation Cold temperature, high entropy
Heatengine
Power
MotionHeat flux
Atmosphere
Radiativeexchange
Thermodynamics sets limits to work and energy conversions
E
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IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
Thermodynamics
31
Solar radiation
Not reflected70%
Solar radiative heating
Differential heating
Atmospheric circulation
Oceanwaves
Oceanic circulation
≈ 175000 TW
Geometric differences40%
Maximum power efficiency2%
≈ 123000 TW
≈ 49000 TW
≈ 1000 TW
Conversion6%
≈ 60 TW
≈ 5 TW
Conversion8%
Work done by Earth system processes is small compared to radiative fluxes, but
essential to maintain dynamics
Comparison: 17 TW of human primary energy consumption
(0.4 TW in Germany)Kleidon (in press)
1 TW = 1012 W
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IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
Thermodynamics
• The ideal gas law describes relationship between pressure p and temperature T of air. It is typically expressed for air in terms of air density ρ and the gas constant Ra as
• very often used to determine air density!
32
p = ⇢RaT
E
T temperature K
Ra gas constant for air 287 J kg -1 K-1
ρ density kg m-3
p pressure Pa
T (in °C) ρ (in kg m-3)0 1,2935 1,270
10 1,24815 1,22620 1,20525 1,18530 1,165 at p = 1013.25 hPa
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IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
3. Atmospheric Structure
33
The basic structure of the atmosphere in terms of vertical temperature and pressure variations can be derived from simple physics.
First law: conserve total energy (heat + potential) when air is lifted by dz
cpdT + gdz = 0
Hydrostatic balance: balance of gravity with pressure drop across a layer of thickness dz:
dp = ��gdz
Ecommonly used to convert pressure into heighteffect of moisture?
33
IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
Atmospheric Structure
When air is lifted adiabatically (no heat exchange), pressure and temperature changes. To make air parcels comparable, a potential temperature is introduced.The potential temperature θ isdefined as the temperature ofair with (T, p) when brought toa reference pressure p0:
- is derived from heat engine- is used to determine vertical motion
34
� = T
✓p0p
◆R/cp
R/cp: !2/7p0: ! Reference pressure
(p0 = 1000 hPa)
Equator SN
300 K
350 K
200 K
300 K
260 K
100 hPa
10 hPa
1000 hPa
100 hPa
1000 hPa
1 hPa
260 K260 K
Source: ECMWF - ERA40
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IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
Atmospheric Structure
35
Example: Radiosounding, Meteorological Observatory Lindenberg, 09. Juli 2011; 12h
Temperaturpotentielle Temperatur
Höh
e (m
)
0
2500
5000
7500
10000
12500
15000
Temperatur (°C)−60 −40 −20 0 20 40 60 80 100
Hei
ght (
m)
Temperature (°C)
T
Hei
ght (
m)
θ
Pressure[hPa]
Temperature [°C]
Height[m]
pot. Temp.[K]
1002 27,0 115 26,8
1000 25,8 132 25,8
925 19,0 810 25,6
850 12,0 1528 25,6
752 4,8 2542 28,4
http://weather.uwyo.edu/upperair/sounding.html
observed inferred
35
Lunch Break
we meet again at 14:00
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IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
Solar radiation is the primary forcing of the Earth system. Its magnitude and its variation is governed by radiation laws.
• Radiation is characterized by wavelength λ (“lambda”, unit: m) or frequency ν (“nu”, unit: Hz = 1/s)
• Relationship between wavelength and frequency:
• Wave-particle (“photon”) dualism, with photon energy (“quantum”):
• Every object with a temperature emits radiation according to the Stefan-Boltzmann law:
• Peak emission occurs at a wavelength λmax given by Wien’s displacement law:
4. Solar radiation
37
c = � · ⌫
E = h⌫
R = � · T 4
�max
T = bT temperature in Kelvinc speed of light 3 108 m s-1
h Planck constant 6.63 10-34 Jsσ Stefan-Boltzmann constant 5.67 10-8 W m-2 K-4
b constant 2.8978 10-3 m K E
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IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
Radiative Spectra
38
The emission spectra for T = 5760K and T = 255K (relative intensity) are well-separated. This results in the separation between solar vs. terrestrial radiation.
0
0.2
0.4
0.6
0.8
1.0
0.1 1 10 1000
0.2
0.4
0.6
0.8
1.0
0.1 1 10 100
Rel
ativ
e in
tens
ity
Rout = 342 W m-2
EarthSolar radiation(low entropy)
Reflected solar and reemitted terrestrial radiation
(high entropy)
Rin = 342 W m-2
Wavelength (µm)
Irreversible processes
Tsun= 5760 K
Wavelength (µm)
Rel
ativ
e in
tens
ity Tearth = 255 K
scattered
re-emitted
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IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
The magnitude of solar radiation at a given place on Earth is determined by the solar luminosity, the distance between the Sun and the Earth, and the orientation of the Earth’s surface.
SunEarth
Solar Radiation on Earth
Solar luminosity:L0 = 3.9 1026 W
I =L0
4π · d2
Radiative flux atdistance d:
DistanceEarth-Sun:
d = 150 109 m
I = 1379 W m-2
39
Solar “constant”:Mean influx: I/4 = 345 W m-2
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IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
Variations in Solar Radiation
Variations in solar radiation are caused by:
1. Solar activity (e.g. luminosity)2. Orientation of surfaces to solar radiation3. Aspects of Earth’s orbit (e.g. distance)
Sun Earth
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IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
Variations in Solar Activity
• Millions of years:• increase of solar activity over time• 4.5 billion years ago, 70% of today’s luminosity
• Thousands of years • interannual: “sunspot” cycle
approx. 11 years
science.nasa.gov/ssl/pad/solar/sunspots.htmwww.sel.noaa.gov
41
starting in 1750
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IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
Orientation of Surfaces
Sun
January
July
vernal
equinox
autumnal
equinox
distance to perihelion
147,000,000 km
summer
solstice
distance to aphelion
152,000,000 km
winter
solstice
April
October Arctic circle (winter)
Tropic of cancer
Tropic of capricorn
Antarctic circle (summer)
Equator
tilt
(obliquity)
North pole
South pole
42
E
I =L0
4π · d2
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IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
Orientation of Surfaces
Sun
sola
r rad
iatio
n
AB
C
Sun
Sun
A:
B:
C:
= 90°
0° < < 90°
= 0°
declinationangle
Earth
Equator
North pole
South pole
Arctic circleTropic of cancer
Tropic of capricorn
Antarctic circle
43
Definition of zenith angle θ: Sun
sola
r rad
iatio
n
AB
C
Sun
Sun
A:
B:
C:
= 90°
0° < < 90°
= 0°
declinationangle
Earth
Equator
North pole
South pole
Arctic circleTropic of cancer
Tropic of capricorn
Antarctic circle
E
cos ✓ = sin lat · sin � + cos lat · cos � · coshourCalculation of the zenith angle:
lat: ! latitude in degree δ: ! declination angle (-23.5° at winter solstice, 0° at equinox, 23.5° at summer solstice; otherwise more ! complicated to calculate)hour:! time in degree (0° = noon)
Is = I? · cos✓Accounting for solar inclination:
43
IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
Orientation of Surfaces
• Insolation-weighted daily average solar zenith angle as a function of latitude:
44
Hartmann, Fig. 2.8
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IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
Orientation of Surfaces
• Seasonal and latitudinal variation of solar irradiation in W m-2
45
Hartmann, Figure 2.6
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IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
Orbital Variations
Three orbital parameters of the Earth vary on time scales of thousands of years: eccentricity (related to distances of perihelion and aphelion), timing of perihelion (precession), and tilt (obliquity)
46
Sun
January
July
vernal
equinox
autumnal
equinox
distance to perihelion
147,000,000 km
summer
solstice
distance to aphelion
152,000,000 km
winter
solstice
April
October Arctic circle (winter)
Tropic of cancer
Tropic of capricorn
Antarctic circle (summer)
Equator
tilt
(obliquity)
North pole
South pole
evidence from ocean and ice cores supports orbital causes for ice ages
altered orbital parameters alter seasonal insolation patterns, particularly near the poles
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IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
5. Global energy balance
47
team view of the closure for the TOA radiation budget. The TOA imbalance in the original CERES products is reduced by making largest changes to account for the uncertainties in the CERES instrument absolute calibration. They also use a lower value for solar irradiance taken from the recent TIM observations (Kopp et al. 2005).
Several atlases exist of surface f lux data, but they are fraught with global biases of several tens of watts per meter squared in unconstrained VOS observation-based products (Grist and Josey 2003) that show up, especially when net surface flux fields are globally averaged. These include some based on bulk flux formulas and in situ measurements, such as the Southampton Oceanographic Centre (SOC) from Grist and Josey (2003), WHOI (Yu et al. 2004; Yu and Weller 2007), and satellite data, such as the HOAPS data, now available as HOAPS version 3 (Bentamy et al. 2003; Schlosser and Houser 2007). The latter find that space-based precipitation P and evapora-tion E estimates are globally out of balance by about an unphysical 5%. There are also spurious variations over time as new satellites and instruments become part of the observing system.
Zhang et al. (2006) find uncertainties in ISCCP-FD surface radiative fluxes of 10–15 W m−2 that arise from uncertainties in both near-surface temperatures and tropospheric humidity. Zhang et al. (2007) computed surface ocean energy budgets in more detail by com-bining radiative results from ISSCP-FD with three
surface turbulent f lux estimates, from HOAPS-2, NCEP reanalyses, and WHOI (Yu et al. 2004). On average, the oceans surface energy flux was +21 W m−2 (downward), indicating that major biases are present. They suggest that the net surface radiative heating may be slightly too large (Zhang et al. 2004), but also that latent heat flux variations are too large.
There are spurious trends in the ISCCP data (e.g., Dai et al. 2006) and evidence of discontinuities at times of satellite transitions. For instance, Zhang et al. (20007) report earlier excellent agreement of ISCCP-FD with the ERBS series of measurements in the tropics, including the decadal variability. However, the ERBS data have been reprocessed (Wong et al. 2006), and no significant trend now exists in the OLR, suggesting that the previous agree-ment was fortuitous (Trenberth et al. 2007b).
Estimates of the implied ocean heat transport from the NRA, indirect residual techniques, and some coupled models are in reasonable agreement with hydrographic observations (Trenberth and Caron 2001; Grist and Josey 2003; Trenberth and Fasullo 2008). However, the hydrographic observations also contain significant uncertainties resulting from both large natural variability and assumptions associated with their indirect estimation of the heat transport, and these must be recognized when using them to evaluate the various flux products. Nevertheless, the ocean heat transport implied by the surface fluxes provides a useful metric and constraint for evaluating
products.
THE GLOBAL MEAN ENERGY BUDGET. The results are given here in Table 1 for the ERBE period, Table 2 for the CERES period, and Fig. 1 also for the CERES period. The tables present results from several sources and for land, ocean, and global domains. Slight differences exist in the land and ocean masks, so that the global value may consist of slight-ly different weights for each component.
ERBE period results . For the ERBE period, Table 1 presents results from KT97 for comparison with those
FIG. 1. The global annual mean Earth’s energy budget for the Mar 2000 to May 2004 period (W m–2). The broad arrows indicate the schematic flow of energy in proportion to their importance.
314 MARCH 2009|
Trenberth et al. (2009)
Ts ≈ 288 K
47
IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
Global Energy Balance
• The global energy balance in steady state balances absorbed solar radiation with emitted terrestrial radiation.
• Simplest energy balance yields the radiative temperature of a planet
• Planetary albedo describesthe fraction of reflected radiationresulting from ice, clouds, …• example surface albedo values:
ice ≈ 0.6; desert ≈ 0.35; rainforest ≈ 0.14; ocean ≈ 0.06
• Earth’s radiative temperature: Tr ≈ 255 K
48
I
4(1 − ap) − σT 4
r = 0
T temperature K
αp planetary albedo 0,3
I solar constant 1367 W m-2
σ Stefan-Boltzmann const 5.67 10-8 W m-2 K-4
48
IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
Planetary Albedo
Venus Earth Mars
albedo = 0.71 albedo = 0.3 albedo = 0.16
49
E
d = 108 106 km d = 249 106 kmd = 150 106 km
49
IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
Greenhouse Effect
• A very simple, two-layer model of the surface-atmosphere to demonstrate the importance of the greenhouse effect
50
atmosphere
surface 0 = Rs,in(1� a)� �T 4s + �T 4
a
0 = �T 4s � 2�T 4
a
Greenhouseforcing
E
50
IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
6. DynamicsMotion results mostly from buoyancy, i.e., density differences, and related effects (especially in the vertical).
51
State B: State C:State A:
ρl
ρh
heavier fluid with density
ρh
lighter fluid with density ρl
lighter fluid rises due to buoyancy
lighter fluid spreads (if possible)
51
IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
DynamicsDifferences in density are caused by temperature differences (due to heating and cooling) and salinity differences (ocean, mostly due to evaporation - precipitation)
52
1.15
1.20
1.25
1.30
1.35
1.40
−20 −10 0 10 20 30
Salin
ity (‰
)
40
0
20
30
10
0 10 20 30Temperature (°C)Temperature (°C)
Den
sity
(kg
m-3
) Density - 1000 (kg m-3)
Atmosphere:ideal gas law
Ocean:empirical formula
52
IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
Dynamics
A simple upper bound to large-scale heat transport by motion can be inferred from a simple 2-box model and thermodynamics.energy balances of two boxes:
Carnot limit describes limit of converting heat into work:
here: ! Pmax: !generation of kinetic energy!! J: ! ! heat transport
53
Pmax
= J · Th
� Tc
Th
= J · �T
Th
Jin,h Jout,cJin,cJout,h
TcTh
Atmospheric heat engineJ
P
Tropics Extratropics
Solarradiation
Terrestrialradiation
0 = Jin,h
� Jout,h
� J0 = J
in,c
� Jout,c
+ J
E
53
IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
Dynamics
Steps to a estimate:- use a simple approximation for emission of radiation (instead of Stefan-Boltzmann law):
- with energy balances yields an expression for ∆T (note: heat flux attempts to deplete gradient):
- results in a quadratic function of Pmax:
- yields a maximum estimate of:
- estimate: ∆Jin ≈ 98 W m-2; Jopt ≈ 24 W m-2 [obs: 23 W m-2]
54
Jout
(T ) ⇡ J0 + kT
�T =�Jin � 2J
kPmax
= J · �Jin
� 2J
kTh
Jopt
=�J
in
4Pmax
=(�J
in
)2
8kTh
54
IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
Dynamics
-200
-100
0
100
200
300
400
Rad
iativ
e Fl
ux (W
m-2)
-90 -60 -30 0 30 60 90
-5.0
-2.5
0.0
2.5
5.0
7.5
10.0
Wat
er F
lux
(mm
d-1)
-90 -60 -30 0 30 60 90
Latitude
-50
0
50
100
150
200
250
Ener
gy F
lux
(W m
-2)
-90 -60 -30 0 30 60 90
NorthSouth
top of atmosphere
surface
solar
terrestrial
net
net
solar
terrestrial
latent heat
sensible heat
precipitation
evaporation
net
55
• Top: zonal means of solar and terrestrial radiation at the top of the atmosphere
• Difference between solar and terrestrial radiation (net) describes net heat transport
• Middle: surface energy balance components
• Bottom: differences in precipitation and evaporation imply differences in moisture transport by atmospheric dynamics
• Release of latent heat by precipitation causes moist convection and generation of motion, esp. in the tropics, which results in strong coupling between energy fluxes, hydrologic cycling, and generation of motion
ECMWF reanalysis
55
IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
Biogeochemical Cycles: Overview
• Global cycles of water and carbon
• Residence times vs. spatial and temporal variations
• Planetary evolution
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IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
Global Hydrologic Cycle
Estimates of reservoirs and fluxes of the global hydrologic cycle in 1012 m3 and 1012 m3 yr-1
57
Atmosphere
Ocean Land
Lithosphere
1 348 000
13
22 780
2258062
Soils
Groundwater
361324
99 62…
E
57
IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
Global Carbon Cycle
Estimates of reservoirs and fluxes of the global carbon cycle in 1012 kg C and 1012 kg C yr-1
58
Atmosphere
Ocean Land
Lithosphere
38 000
750
1500 Soils
9090
120 60
E
500Vegetation
60
58
IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
Biogeochemical Cycles
Residence times include information about how fast a stock can change for a given flux.
59
Precipitable water(0 - 50 kg m-2)
Atm. CO2 concentrations(350-380 ppmv)
59
IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
Biogeochemical Cycles
Catling (2004)
60
The atmospheric composition of Earth has likely changed substantially throughout its history, mostly due to biotic activity.
Human Society
Biosphere
FossilBiomass
MarineTerrestrial
Ene
rgy
Cap
ture
(EJ/
y)
anox
ygen
ic p
hoto
synt
hesi
s
oxyg
enic
pho
tosy
nthe
sis
land
pla
nts
pale
olith
ic fir
e us
e
neol
ithic
revo
lutio
n
~3 Ga ~1.5 Ga ~350 Ma ~10,000 BCE ~1850 CE ~2000 CE
10-1
100
101
102
103
104
indu
stria
l rev
olut
ion
Figure 1. Energy capture in the biosphere and human society. Data and sources in Table S1.
O2 persistently >15% of the atmosphere since 370 Ma (Belcher and McElwain, 2008; Scott and315
Glaspool, 2006).
The rise in atmospheric oxygen and increase in food supply brought about by land plants has
allowed a flourishing of animal complexity from aerobic pathways – including the emergence of us
humans. Today, the total global energy flux through heterotrophic biomass, based on a 10% conver-
sion efficiency of 100 PgC yr�1 with energy density 40 kJ gC�1, is ⇠ 400 EJ yr�1, roughly half on320
land and half in the ocean. Natural fires additionally consume ⇠ 55 EJ yr�1 (1.4 PgC yr�1) (Eliseev
et al., 2014), and human-induced fires ⇠ 45 EJ yr�1 (1.1 PgC yr�1) (Haberl et al., 2007), giving a
total biomass burning flux today of ⇠ 100 EJ yr�1 (⇠ 2.5 PgC yr�1) (Randerson et al., 2012), or
⇠ 2.5% of the energy and carbon captured in photosynthesis.
3 Revolutions in human history325
Like all animals humans are heterotrophs. Our biological metabolism relies on the products of pho-
tosynthesis. At the same time humans are exceptional among animals in creating and maintaining
a social metabolism via breeding and cultivating plants and animals, in constructing buildings and
large infrastructure systems and in producing numerous artifacts (Fischer-Kowalski and Hüttler,
1998). The social metabolism inevitably extends total human energy capture and material use be-330
yond the biological requirements. In modern industrial societies the amount of energy and materials
used to produce and reproduce domesticated livestock and all artifacts typically is an order of mag-
nitude larger than the basic biological metabolism of the human population itself. For the following
comparison between human energy use and the primary productivity of the entire biosphere, it is
therefore important to keep in mind the different trophic levels involved, autotrophs versus het-335
10
Lenton et al (in discussion, ESDD)
Over Earth evolution, the energy capture (power and dissipation) by life (and humans) likely increased substantially.
60
IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
Biogeochemical Cycles
goddess of spring (Retallack, 2000b), is undeni-able for the annual spring fall and autumn rise ofatmospheric CO2 with northern hemisphere leafsprouting and shedding (Figure 2(a)). Thisexplanation is especially demonstrated by themuted and out-of-phase annual fluctuation of CO2
in the southern hemisphere (Mooney et al., 1987),where there is less fertile land, more evergreenplants, and different seasons. The questionaddressed here is whether the Proserpina principleoperates on geologically significant timescales,and so far, such a simple idea does not conflictwith the history of life and paleoclimate outlinedhere.On evolutionary timescales, it is the biochemi-
cal evolution of lignin, pyrethrin, caffeine, andother substances that deter herbivory, digestion,and decay, which affect rates of carbon burial insediments as the principal long-term control onatmospheric CO2 levels. The role of trees andtheir soils in Late Paleozoic carbon seques-tration, cooling, and glaciation is widely accepted(Berner, 1997; Algeo and Scheckler, 1998; seeChapter 5.06). The role of humans in globalwarming is also becoming well known (Vitouseket al., 1997b). According to the Proserpinaprinciple, we may not have been the onlyorganisms to have had significant effects onclimate. There remain many other instances ofglobal change less clearly related to changes inlife and soils, in part because the numerouspaleosols of appropriate age have not yet beenstudied in detail. Asteroid impacts, volcaniceruptions, and methane clathrate dissociation
events also affect life and the carbon cycle,producing transient greenhouse events (Retallack,2001b). Ocean currents and mountain buildingalso are likely to play a role in carbon sequestra-tion (Raymo and Ruddiman, 1992;Ramstein et al.,1997). Soils and their ecosystems play animportant role in the carbon cycle today, andthe history of that role now decipherablefrom paleosols appears ripe for modeling andother quantitative comparisons with other likelycontrols on global paleoclimate change.
ACKNOWLEDGMENTS
Nathan Sheldon, Hope Jahren, and Tim Whitehave been sounding boards for the ideas presentedhere. I also thank J. I. Drever and H. D. Hollandfor helpful reviews.
REFERENCES
Algeo T. J. and Scheckler S. E. (1998) Terrestrial–marineteleconnections in the Devonian: links between the evolutionof land plants, weathering processes and anoxic events. Roy.Soc. London Phil. Trans. B353, 113–130.
Allen J. R. L. (1974) Geomorphology of Siluro-Devonianalluvial plains. Nature 249, 644–645.
Amundson R., Stern L., Baisden T., and Wang Y. (1998) Theisotopic composition of soil and respired CO2.Geoderma 82,83–114.
Bakker R. T. (1985) The Dinosaur Heresies.WilliamMorrow,New York.
Barley M. E., Pickard A. L., and Sylvester P. J. (1997)Emplacement of a large igneous province as a possible causeof banded iron formation 2.45 billion years ago. Nature 385,55–58.
Figure 16 The Proserpina principle relates variation in atmospheric CO2 concentration with coeval evolutionaryand ecological events on a variety of timescales. Carbon sequestering evolutionary innovations and ecologicaltransitions (closed symbols) alternate with carbon oxidizing evolutionary innovations and ecological transitions
(open symbols). The CO2 curve is a composite of those shown in Figure 2 and by Kasting (1992).
Soils and Global Change in the Carbon Cycle over Geological Time600
Retallack (2004)
Evolution of atmospheric CO2 and biotic events
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IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
Biogeochemical Cycles
© Nature Publishing Group1965
Lovelock (1965) on habitability and life
Lovelock (1975): atmospheric composition
6262
IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
Biotic Activity in the Earth System
63
Kleidon (in press)
Solarradiation
Differentialheating
Motion
Interiorcooling
Hydrologiccycling
Geochemicalcycling
Motion
Bioticactivity
Humanactivity
Photochemicalconversion
Thermalconversion
Photochemicalconversion
Radiativeconversion(potential)
cycling activity activity
Interior Earth
175000
123000
4600
20
< 22
21528 8
1000
< 12% < 93%< 12%
25Thermalconversion
All estimates in 1012 W
Atmosphere
Fossilfuels
17
The strong effect of biotic activity on the Earth system can be identified by the rate by which life generates chemical free energy by photosynthesis.
Estimates of planetary drivers and energy conversion limits for different Earth system processes. Black arrows indicate flows of energy, while dashed arrows indicate the effects of mass exchange limitations. All estimates are given in units of 1012 W.
63
IMPRS-BGC: Module “Atmosphere” – Day 1 – slide Kleidon 02/2016
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