Title: Lecture 3a: Radiation in the Atmosphere and Climate (Chapter 2)
1Lecture 3a Radiation in the Atmosphereand
Climate(Chapter 2)
2Solar constant and solar radiation
3Radiation processes in the atmosphere
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5Wave spectrum Short wave Long wave
6Climate Forcing
The ultimate driving force on the earth the
sun Solar constant is the average solar
radiation that reaches the earth on a
perpendicular plane to the sun ray (total area
?R2) S01368 W/m2 . Short wave radiation (solar
radiation) is normally the average solar
radiation on the surface of the spherical earth
(total area 4?R2) S S0/4342 W/m2 Long wave
radiation (terrestrial radiation) is the back
radiation to the space by the earth with an
effective temperature T as Q?T4 , where
?5.67 ?10-8 W/m2K4 is the Stefan-Boltzman
constant.
7Blackbody radiation
A blackbody at temperature (in K) radiates energy
at different wave length ? as
where
are constants. The radiation has a maximum value
at the wavelength
?maxa/T, where a2897 ?m K.
Integrated in all the wavelength, we have the
radiation energy flux as E?T4
8Why tropics is warmer than the poles?
Latitudinal distribution
9 Latitudinal distribution pole-equator
contrast, implication for circulation
10Why summer is warmer than winter?
Four seasons
11Why climate is different in different regions
Continental vs Marine Climate
Annual temperature range
12Land sea contrast Thermal inertial
13Why the Earth surface temperature is about 15oC
(288K)?
- Climate modeling
- Global Mean (0-Dimension) climate model
- Radiative equilibrium climate models (Lecture 3
Note. A)
14Radiative Equilibrium Model
Total heat flux across the surface S - ? T4
0 T c (S/ ?)1/4 , S342 Wm2 ? T c
279oK6oC, Too cold! ,
15Cloud Albedo Effect Radiative Equilibrium Model
Total heat flux across the surface (1-a)S - ?
T4 0 T cc (1-a)S/ ?1/4 , ? T cc
255oK -18oC Even colder
16Greenhouse Effect (H2O!)
Heat fluxes surface (1-a)S ? Tg4 - ? T4
0 Top (1-a)S - ? Tg4 0 (or
radiation balance for the glass layer 2? Tg4
? T4 ) Tg ((1-a)S/ ?)1/4 Tcc255K , ? Tcg
21/4Tg288oK15oC About right
17How does the climate respond to global warming
forcing?
CO2 induced Radiative Forcing Climate Sensitivity
18CO2 induced Radiative Forcing
- RF 5.25 ln (CO2) W/m2 (S.
Arrhenius, 1900) - Examples Present relative to 1850 (CO2 250ppm)
- RF5.25 ln (385 / 250 ppm) 2.5 W/m2
- Doubliing CO2
- RF5.25 ln (500 / 250 ppm) 4 W/m2
Climate Sensitivity ?TbRF b
climate sensitivity! increase in
temperature per unit increase in
radiative forcing
19Svante Arrhenius
Born 19 February 1859(1859-02-19)Vik, Sweden
Died 2 October 1927(1927-10-02) (aged 68)Stockholm, Sweden
Nationality Swedish
Fields Physics, chemistry
Institutions Royal Institute of Technology
Alma mater Uppsala UniversityStockholm University
Doctoral advisor Per Teodor Cleve, Erik Edlund
Doctoral students Oskar Benjamin Klein
Known for Arrhenius equationTheory of ionic dissociationAcid-base theory
Notable awards Nobel Prize for Chemistry (1903)Franklin Medal (1920
20Global Warming ResponseRadiative Equilibrium
Model
RF(CO2)
Global warming prediction
Total flux S RF- ? T4 0 T (SRF)/
?1/4 (S/ ?)1/4 bRF Tc bRF,
here RFltltS or global warming ?T T- Tc
bRF Climate sensitivity bd (S/ ?)1/4 /dS
1/(4 ?Tc 3)0.2 K / Wm-2 ? Double CO2
?T bRF 0.2 4 0.8oK, small??
21Cloud Albedo Effect Radiative Equilibrium Model
Total heat flux across the surface (1-a)S RF-
? T4 0 T cc (1-a)S/ ?1/4 , ? T cc
255oK -18oC Climate sensitivity b1/(4
?Tcc 3)0.37 K / Wm-2 Double CO2 ?T
bRF 0.37 4 1.5oK greater
!
22Greenhouse Effect (H2O!)
Heat fluxes surface (1-a)S RF-? Tg4 - ?
T4 0 Top (1-a)S RF-? Tg4 0 T
cg 2(1-a)S/ ?1/4 288oK15oC Now climate
sensitivity , b1/(4 ?Tcg 3)0.45 K /
Wm-2 Double CO2 ?T bRF 0.45 4
1.8 2oK, even greater !
23Svante Arrhenius
To explain the ice age, Arrhenius estimated that
halving of CO2 would decrease temperatures by 4 -
5 C (Celsius) and a doubling of CO2 would cause
a temperature rise of 5 - 6 C. In his 1906
publication, Arrhenius adjusted the value
downwards to 1.6 C (including water vapour
feedback 2.1 C). Recent (2007) estimates from
IPCC say this value (the Climate sensitivity) is
likely to be between 2 and 4.5 C. Arrhenius
expected CO2 doubling to take about 3000 years
it is now estimated in most scenarios to take
about a century.
24Lecture 3b Heat Transfer in the
Atmosphere(Chapter 2)
25Convection, Stratification
26Latitudinal Differential Heating-- The driving
force for circulation
27Atmospheric General Circulation
28Rotation
29Coriolis force
30Monsoon, precipitation
31monsoons
32Subtropical High
H
Geostrophic flow
33Surface temperature, Clouds
Extratropical cyclones
Tropical convection
Extratropical cyclones
34Infrared Images
Extratropical cyclones
Tropical convection
Extratropical cyclones
35Water vapor content
36Extratropical Cyclone, Storm Track
Infrared (long wave)
Visible light (short wave)
Water vapor
37Regional climate Regional topographic effect
38Vertical structure of the atmosphere
39Vertical mass distribution
Troposphere
40The Role of Water Fuel for the Climate Heat
Engine Hydrological Cycle
41Latent heat of melting and vaporization
42Water vapor content
43Lecture 3c Heat Transfer in the Ocean(Chapter
2)
44Ocean Circulation, Ocean Gyres
45How does wind drives the ocean?
Ekman flow Ekman spiral Ekman layer
46Ocean gyres
47Vertical temperature structure Thermocline
48Wind-driven Upwelling
49Overturning circulation
50Thermohaline circulation
51Thermo--haline circulation
Equator Saline
North Pole Fresh
Equator Warm
North Pole Cold
Haline circulation
Thermal circulation
Thermo-Haline circulation
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53 Schematic figure of various branches of climatic
teleconnections in the atmosphere and ocean. The
atmospheric teleconnections occur at fast time
scales, usually shorter than monthly to seasonal
(not marked). The oceanic teleconnection occurs
at a wide range of time scales as marked.
54Lecture 3d Climate Modeling(Chapter 2)
55Climate Modeling
- General Circulation Model
- Energy Balance Model
- (L3 Note.B)
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57CCSM3 (T31_gx3v5) Dyn Veg
TRACE-21 Experiment Set Up
- Atmosphere (CAMT31)
- 3.75o x 3.75o x 26 level
- Ocean (POPSea Ice)
- 3 to 0.5o on equator
- Land (CLMLPJ)
- Forcing
- realistic orbital, GHGs,
- continental ice sheet (ICE-5G, each 500-yr)
- land sea mask (twice)
Meltwater No. 1 uncertainty!
58Earth System Model
Biogeochemical Cycle (e.g. Carbon cycle)
59Test Climate ModelClimate Sensitivity
- From last glacial era, we know this is roughly 5
C per 7 W/m2 - glacial to post-glacial
- This amounts to 0.75 C / W m-2
- IPCC says for doubling of CO2, should expect 1-6
C of warming
60LGM Climate
CLIMAP SST
Model SST
Model Tair
1) CO2 vs. ice sheet 2) Proxy uncertainty vs.
model uncertainty
Liu et al., 2002, GRL
61The End Lecture 3