1. Natural Environments: The Atmosphere
GG 101 – Spring 2005
Boston University
Myneni
Lecture 07: Atmosphere-Surface-Energy-Budget
Feb-04-05
(6 of 12)
Shortwave Radiation Budget
Typically, to aid with discussion, we use ‘dimensionless units’ where 100 represents an
amount equal to what comes from the sun
Reflection (Albedo):
3% reflected to space by atmosphere
19% reflected by clouds
9% reflected by the surface
Absorption in the atmosphere:
18% absorbed by atmosphere
3% absorbed by clouds
Absorption by the surface:
48% absorbed at the surface
This radiation is absorbed, heats the surface
and is converted to
Longwave radiation
Sensible and latent heat

2. Natural Environments: The Atmosphere
GG 101 – Spring 2005
Boston University
Myneni
Lecture 07: Atmosphere-Surface-Energy-Budget
Feb-04-05
(8 of 12)
Longwave Radiation Budget
We will continue use the dimensional units
From surface:
6% escapes to space
107% is radiated by surface and
absorbed by atmosphere
From Atmosphere:
97% is re-radiated by atmosphere and is
absorbed by the surface
63% is re-radiated to atmosphere and
escapes
Why is more radiation emitted from the surface of the earth than is absorbed through solar radiation?
Because of the “Natural Greenhouse Effect”

3. Natural Environments: The Atmosphere
GG 101 – Spring 2005
Boston University
Myneni
Lecture 07: Atmosphere-Surface-Energy-Budget
Feb-04-05
(10 of 12)
Surface Radiation Balance 48
Solar Radiation
Heating
Incoming Solar Radiation 48
Incoming Longwave Radiation 97
Total
Cooling
Outgoing Longwave Radiation 113
Latent Heat 22
Sensible Heat 10
Total

4. Natural Environments: The Atmosphere
GG 101 – Spring 2005
Boston University
Myneni
Lecture 07: Atmosphere-Surface-Energy-Budget
Feb-04-05
(11 of 12)
Atmospheric Radiation Balance
Heating
Cooling
Incoming Solar Radiation 21
Incoming Longwave Radiation 107
Latent Heat 22
Sensible Heat 10
Total
Outgoing Longwave Radiation
(to space) 63
(to Earth) 97
Total

5. Natural Environments: The Atmosphere
GG 101 – Spring 2005
Boston University
Myneni
Lecture 07: Atmosphere-Surface-Energy-Budget
Feb-04-05
(12 of 12)
Global Radiation Balance
Incoming Solar Radiation 100
Total
Reflected to space 31
Longwave Radiation from Earth 6
Longwave Radiation from Atmos. 63
Total

6. CLOUD GREENHOUSE FORCING
A simplified model of the Earth-Atmosphere energy system – notice that incoming transmission of daytime solar radiation is balanced by outputs of earth radiation transmission at night.
CLOUD ALBEDO FORCING
Cloud Albedo Forcing refers to an increase in albedo caused by reflection of solar radiation by clouds (A)
CLOUD GREENHOUSE FORCING
Cloud Greenhouse Forcing refers to an increase in atmospheric temperatures caused by absorption of solar radiation by clouds (B)
NIGHT A
DAY B

7. HIGH CLOUDS HAVE A NET GREENHOUSE FORCING & ATMOSPHERIC WARMING EFFECT
(A): High clouds [ice-crystals cirrus clouds] transmit almost all of insolation but absorb & delay outgoing long wave terrestrial radiation, producing a net-warming effect
LOW CLOUDS HAVE A NET ALBEDO FORCING & ATMOSPHERIC COOLING EFFECT
(B): Low clouds [thick stratus/cumulonimbus clouds] reflect most of incoming shortwave & radiate long wave infrared to space, producing a net-cooling effect