Transcript Global Ocean Air-sea CO2 fluxes

Earth System and Climate:
Introduction (ESC-I)
Coordinators:
V. Valsala, R. Murtugudde and M. Baba
Contents of ESC-Intro. course:
• Earth System Science and Global Climate Change G
• Global Energy Balance
P
• Global Carbon Cycle
C
• Recycling of Elements; C, N, O2, O3 depletion
C
• Global Biogeochemical Cycle- oceans
C/B
• Short-term Climate variability, Global Warming P/C/B
Should be covered in 7-hours
Where does the energy for
earth system come from?
© http://en.wikipedia.org/wiki/Solar_System
Continuous supply of energy for the
earth systems- Solar Energy
The solar
energy drives
the earth’s
atmosphere
and ocean.
Energy from sun’s radiation.
Nearly all the
energy being
at
wavelengths
0.2µm to 4µm
Electro Magnetic spectrum of
solar radiation
-----10% of energy--
-----40% of energy------
---------50% of energy------
Blackbody radiation flux
Wein’s law λmax = 2898/T
Stefan-Botlzmann law F = σT4
Amount of radiation receives at
surface of Earth
Solar constant (S ~ 1368 W/m2)
• S  definition; Average energy ‘flux’
Solar heat flux
from the sun at a mean radius of earth
Latitude
Reflectivity of earth surface and
atmosphere  Albedo.
• Albedo The relative amount of solar
insolation reflected back to the space
by means of reflection by the earth
surface as well as the atmosphere.
Average albedo of
earth ~ 0.3.
Therefore net heat
flux received from
sun = 240W/m2
With an average of 240w/m2
influx from the sun, how much
would be the atmospheric
temperature?
Earth with
no-atmosphere.
Earth with
atmosphere.
E = σT4
E = 240 w/m2
σ = 5.7x10-8 W/m2/k4
T = 250 Kelvin (~ -200C)
E = σT4
E = 240 w/m2
= 5.7x10-8 W/m2/k4
Green house effect
T = 300 Kelvin (~ 150C)
The Green house effect.
Sun
Earth
GH-effect helps
the atmosphere to
be warm at 150C
The one-layer atmosphere model
of Green-house effects
Ts = 1.19*Te
For average Te=255k,
Ts = 303K
ΔTg = Ts- Te
Adopted from Lee Kump book
Height 
Summary of Greenhouse heat budget (w/m2)
Source: IPCC-AR4 report, 2007
http://www.ipcc.ch/publications_and_data/publications_and_data_reports.shtml
Composition of the atmosphere.
http://en.wikipedia.org/wiki/Atmosphere_of_Earth
Atmospheric Structure
How atmospheric pressure varies with altitude
P = F/A (Pressure = Force exerted on unit
area)
The pressure exerted by atmosphere at sealevel is defined as one atmosphere (atm)
The SI unit of pressure is Pascal (Pa).
1 Pa = 1x10-5 bar = 9.9 x 10-6 atm.
Atmospheric pressure decreases with height.
Atmospheric Structure
Atmospheric pressure decreases by a factor
of 10 for every 16 km increase in altitude.
1
atm at surface
0.1 atm at 16 km
0.01 atm at 32 km …
The vertical structure of the
Atmospheric temperature.
Vertical distribution of Ozone.
Percentage of radiation absorbed
in the atmosphere.
Physical causes of greenhouse effect
Molecules absorbs incident
atmospheric radiation by mean of
increasing its rotation.
Example: Water vapor.
Physical causes of greenhouse effect
Molecules absorbs
incident atmospheric
radiation by mean of
vibration or bending.
Example: CO2
But diatomic symmetric
molecules have little
capacity to absorb
electromagnetic
radiation. Therefore
N2 and O2 are not
greenhouse gases
Effects of clouds on radiation
Types of clouds:
(a) Cumulus clouds: white puffy
clouds that look like balls of cotton.
They are composed of water droplets
and formed by convective activities.
(b) Cumulonimbus clouds: Tall cumulus
clouds giver rise to thunderstorms.
(c) Stratus clouds: They are gray lowlevel water clouds that are more ore
less continuous
Various type clouds with altitude
and temperature
Opposing climate effects of cloud
Have you noticed cloude days are
colder whereas cloudy nights are
warmer?
o Albedo
o Greenhouse effect
Vertical “gradient” of atmospheric temperature
Lapse rate:
•
Definition: “rate at which the temperature of
the atmosphere decreases with height”
• Stability of the atmosphere:
Warm air is lighter than hot air  leads to
vertical motion by virtue of buoyancy (gravity).
height
Unstable
Stable
Cold air
Warm air
Warm air
Cold air
Lapse rate
• Dry (adiabatic) lapse rate
• Moist (adiabatic) lapse rate
Radiative-Convective equilibrium;
-No- horizontal motion models.
Radiative-Convective equilibrium;
with green house effect & no climate
feed back
These model predicts the green house warming
ΔTg = 33 0C
i.e. with CO2 = 300 ppm
In test simulations with doubling the CO2, i.e.
with 600 ppm (expected true value in near
future), the additional ΔTg = 1.2 0C
Why doubling CO2 produce meager changes in
temperature?
Radiation absorption spectrum by CO2 and other
greenhouse gases (H20 vapor) are different
Radiative-Convective equilibrium;
with climate feedbacks
Climate feedbacks are extremely important
because they can either amplify or
moderate the radiative effect of changes
in greenhouse gas concentrations.
We examined the feedbacks in chapter-2
in an imaginary “Daisy world”
We analogically attribute such feedbacks
to the earth system here.
Water vapor feedback
o Water vapor is an excellent absorber of IR
radiation.
o Unlike CO2, water vapor are at the edges
of condensation, and if condenses and rainout, the average vapor concentration in
atmosphere reduces. This can cause
reduction in GH-warming
o On the other hand, if average surface
temperature increases by global warming,
water vapor concentration increases and
that will increase GH-warming further.
Observed Climate changes.
© IPCC-AR4
Satellite derived water vapor (total column water vapor) 1988-2004
(a) Water vapor feed back
Ts
Trend
Atm.
H2O
+ve
GHeffect
Anomaly
Radiative-Convective equilibrium;
with water vapor feedbacks
o Average surface temperature changes in
doubling the CO2 experiment without climate
feedback was 1.2 0C.
o Whereas the above experiment with
watervapor feedback causes the surface
temperature rise by additional 1.2 0C.
o Therefore the total change in temperature
with water vapor feedback is 2.4 0C.
o The feedback factor = 2.4/1.4 = 2 (strong
positive feedback).
Snow-ice albedo feedback
o If surface Ts
increases snow melts
and albedo
decreases
o If albedo decreases
surface temperature
increases
o This leads to a
positive feedback
loop which is
unstable.
Snow-ice feedback
Snow
and Ice
Ts
+ve
Albedo
Infrared-flux and Temperature
feedback
o If surface
Longwave-Temperature feedback
temperature Ts
Longincreases, the
Ts
-ve
wave
outgoing long wave
radiation (infraredflux increase)
o This tends to cool
down the surface
temperature
Climate feed backs of radiation-convection
(a) Water vapor feed back
Ts
Atm.
H2O
(b) Snow-ice feedback
+ve
+ve
Albedo
GHeffect
(c) Longwave-Temperature feedback
Ts
-ve
Snow
and Ice
Ts
Longwave
Conclusion
o Green house and radiation budget.
o Earth is warmed by green house effect
(from -15 0C to 15 0C)
o H2O and CO2 are major GH-gases
o Clouds affect radiation budget both by
reflection and GH-effect.
o Water vapor feedback (+)
o Snow-ice feedback (+)
o Outgoing Longwave Radiation (IR flux) –
surface temperature feedback (-)
Assignment
1. Surface heat budget.
(a) Plot the global and annual
reaching the earth surface
(b) Plot the global and annual
radiation
(c) Plot the global and annual
(d) Plot the global and annual
(e) Plot the global and annual
(f) Plot the global and annual
mean shortwave radiation
mean outgoing longwave
mean
mean
mean
mean
sensible heat flux
latent heat flux
Precipitation rate
Evaporation rate
(g) From figure a to f, comment the total balance of
heat fluxes on annual mean time-scale.
(h) From figure a to f, discuss on the symmetry-asymmetry
structures of the patterns and interpret its causes.
(i) Plot the vertical profile of climatological atmospheric
air-temperature for summer and winter at following locations.
(1) at x=180e,y=0; (2) at x=80e, y=40s;
(3) at x=300e, y=40n; Make a short note on the profiles.