Gravity pulls gases
toward earth's
surface
101.325 kPa
Thermosphere
•250 - 550 km
•temperature rises sharply with height due to
impact of intense sun on N2 and O2 molecules
•not ‘hot’ because kinetic energy of motion not
transferred to particles easily (not sensible heat)
Mesosphere
•temperature falls with height from 0C to
-90C at outer boundary
Stratosphere
•ranges in elevation from 18 km to 50 km
•ozone  temperature rises (-57C to 0C)
•Increasing temperature with altitude prevents
mixing with troposphere (except for some mixing
along jet streams)
Troposphere
•from surface to 8-18 km (normally <11km)
•contains water vapour, clouds, weather, air
pollution and life
•Upper limit (tropopause) is -57C
•Variable environmental lapse rate
(decreasing temperatures with elevation)
UNSTABLE
STABLE
What happens to solar energy ?
1.
Absorption (absorptivity=)
Results in conduction, convection
and long-wave emission
2.
Transmission (transmissivity=)
3.
Reflection (reflectivity=)
 +   +  = 1
Response varies with the surface type
Snow reflects 40 to 95% of solar energy and
requires a phase change to increase above 0°C
Forests and oceans absorb more than dry lands
Then why do dry lands still “heat up” more?
Oceans transmit solar energy and have a high
heat capacity
Characteristics of Radiation
Energy due to rapid oscillations of electromagnetic
fields, transferred by photons
The energy of a photon is equal to
Planck’s constant, multiplied by
the speed of light, divided by the
wavelength
E = hv

All bodies above 0 K emit radiation
Black body emits maximum possible radiation per unit area.
Emissivity,  = 1.0
All bodies have an emissivity between 0 and 1
Electromagnetic Radiation
Consists of electrical field
(E) and magnetic field (M)
Travels at speed of light (C)
The shorter the wavelength,
the higher the frequency
This is important for
understanding information
obtained in remote sensing
Stefan-Boltzmann Law
As the temperature of an object increases, more
radiation is emitted each second
Temperature determines E,  emitted
Higher frequencies (shorter wavelengths) are
emitted from bodies at a higher temperature
Max Planck determined a characteristic
emission curve whose shape is retained for
radiation at 6000 K (Sun) and 300 K (Earth)
Energy emitted = (T0)4
Radiant flux or flux density refers to the rate of flow
of radiation per unit area (eg., Wm-2)
Irradiance =
Emittance =
incident radiant flux density
emitted radiant flux density
Wien’s Displacement Law
As the temperature of a body increases, so does the
total energy and the proportion of shorter wavelengths
max = (2.88 x 10-3)/(T0)
*wavelength in metres
Sun’s max = 0.48 m
Ultraviolet to infrared - 99% short-wave (0.15 to 3.0 m)
Earth’s max = 10 m
Infrared - 99% longwave (3.0 to 100 m)
Terrestrial
radiation
Microwaves are longest
wavelengths used in
remote sensing
Solar
radiation
We are blind to
everything except
this narrow band
UV are shortest
wavelengths practical
for remote sensing
Transmission through the Atmosphere
Some wavelengths of
E-M energy are
absorbed and scattered
more efficiently than
others
H2 O, CO 2, and ozone
have the strongest
absorption spectra
Transmission
Light moves through a
surface (eg. on a natural
surface)
8-11 m window
Wavelength dependent
(eg. leaves)
Radiation emitted from Earth is of
a much longer wavelength and is of
much lesser energy
ALBEDO: April, 2002
white and red
are high albedo,
green and yellow
are low albedo
http://profhorn.aos.wisc.edu/wxwise/AckermanKnox/Earth's Albedochap2/Albedo.html
Characteristic spectral responses of different surface types. Bands are those
of the SPOT remote sensing satellite.
•white snow
•old snow
•vegetation
•light colour soil
•dark colour soil
•clouds
•calm water surface
0.80-0.95
0.40-0.60
0.15-0.30
0.25-0.40
0.10
0.50-0.90
0.10 (midday)
NET ALL_WAVE RADIATION
DAYTIME:
Q* = K - K + L - L
Q* = K* + L*
NIGHT:
Q* = L*
Radiation Balance Components
L
Source: NOAA
Conduction
The transfer of heat from
molecule to molecule
within a substance
Convection and Thermals
Convection
The transfer of heat by
the mass movement of a
substance (eg. air)
Rising air expands and cools
Sinking air is
compressed and
warms
•Heat capacity
The ratio of the amount of heat energy absorbed
by a substance to its temperature rise
•Specific heat
The amount of heat energy required to raise the
temperature of 1g of a substance by 1°C
•Latent heat
The heat energy required to change a substance
from one state to another
•Sensible heat
Heat energy that we can feel and sense with a
thermometer
Radiation Sensors
(PAR and K)
Thermometer
and radiation
shield
SENSIBLE
HEAT
Photo:
My Tausa, Cundinamarca,
Colombia weather station
(3243 m asl)
Raingauge
Datalogger
N
Temperature (C)
20
15
10
5
0
-5
-10
-15
-20
-25
-30
-35
-40
Dec 15, 2004
Jan 19, 2005
10 cm Air Temp (south-facing)
10 cm Air Temp (north facing)
15
Dec 15, 2004
Temperature (C)
10
5
Jan 19, 2005
0
-5
-10
-15
10 cm Soil Temp (south facing)
10 cm Soil Temp (north-facing)
10
Dec 15, 2004
Jan 19, 2005
5
0
-5
-10
-15
-20
-25
-30
-35
-40
-45
10 cm Dewpoint (south facing)
10 cm Dewpoint (north facing)
Check this out:
http://www.jgiesen.de/sunshine/index.htm
10 – 100 m
0.0001 – 0.001 m
Mie scattering
0.01 to 1.0 m
LONG PATH LENGTH OF LIGHT THROUGH
THE EARTH’S ATMOSPHERE
MOST OF THE THE VIOLET, BLUE AND
GREEN LIGHT IS SCATTERED
(from Pacific)
(Prairie cold)