Transcript Discussion on

Discussion on
Prata et al. 1995: Thermal Remote
Sensing of Land Surface Temperature
from Satellite: Current Status and
Future Prospects.
Which range of wavelength of this
paper discuss?
• Shortwave? Near Infrared? Thermal
Infrared?
• What two channels of AVHRR used in LST
retrieval?
two different wavebands, 10.5-11.5μm and
11.5-12.5 μm (channels 4 and 5 in
AVHRR)
• Why this range? (p187)
The important effects
of____________, ___________and
___________________ are
considered and the current practice
for removing these effects is specified.
The important effects
of the atmosphere, surface emissivity and
instrument noise are
considered and the current practice
for removing these effects is specified.
What can LST be used for?
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Calculating SEB (what is 2-way)
In model (what is initialization)
Regional EP estimation
Frost detection
Monitor water-stress in crops
Thermal inertia studies
When LST retrieval started?
retrieval accuracy?
• What is LST retrieval accuracy?
• What is SST retrieval accuracy?
• What is the logic relation between SST
retrieval and LST retrieval?
• Why LST retrieval is ____ than SST
retrieval?
• Discuss: “The land surface presented
particular problems for temperature
determination not evident over the sea”
• Surface Emissivity
• Making a representative measurement of
LST
• The validation of satellite LST
(Definition and meaning of LST)
Section 2: Definition of Surface Temperature
• The ____ channels of AVHH measure the
_______ over an area of approximately
_______ km2
What is its field of view?, what is its pixel size?
Section 2: Definition of Surface Temperature
• After correcting for _____ and _____, the
surface temperature inferred is a _______
Representative of the area corresponding to
the ____________ of instrument?
Section 2: Definition of Surface Temperature
• What is flux definition?
• What is the assumption and basis for such a
definition?
• Why it says “when the surface is not a
blackbody, the definition of the radiative surface
temperature will depend on the ____, and on the
____”?
Section 2: Definition of Surface Temperature
• What is the definition based on planck
function?
Section 2: Definition of Surface Temperature
• What is the thermodynamic measure of
the surface temperature?
• What is numerical model used surface
temperature?
Section 3 Simple and COmples
Land Surface
MODIS Land Cover Classification
(M. A. Friedl, A. H. Strahler et al. – Boston University)
0 Water
1 Evergreen Needleleaf Forest
2 Evergreen Broadleaf Forest
3 Deciduous Needleleaf Forest
4 Deciduous Broadleaf Forest
5 Mixed Forests
6 Closed Shrublands
7 Open Shrublands
8 Woody Savannas
9 Savannas
12 Croplands
13 Urban and Built-Up
14 Cropland/Natural Veg. Mosaic
10 Grasslands
15 Snow and Ice
16 Barren or Sparsely Vegetated
11 Permanent Wetlands
17 Tundra
(Jin and Dickinson 2010, ERL)
Sec. 4
What is Split-window Algorithm?
• The general form of the algorithm is
Eq. (5)
Sobrino et al. notes that in order to gain an LST accuracy of ____,
the spectral emissivity mst be known to an accuracy of _________
Sec. 4
What is Split-window Algorithm?
Prate (1994a) was able to show that LST
accuracies of _________ is possible.
Sobrino et al. notes that in order to gain an LST accuracy of ____,
the spectral emissivity mst be known to an accuracy of _________
Is this LST accuracy practical?
Section 4:
aerosol effect
• The aerosol effect in the _____ is ____,
and often ____, if compared with the effect
in the visible and near infrared regions.
REMOTE SENSING
Surface Temperature
Radiative Transfer equation
The radiance measured by channel i of a satellite sensor. Temperature of
atmosphere is measured by microwave energy emitted by oxygen
Atmospheric effects
• Effect is corrected by
linearizing Planck function
around brightness
temperature in the 10.512.5um waveband.
• Atmospheric correction
– Depends on difference
of brightness
temperature and
temperature of
atmosphere
– Channels used for
NOAA AVHRR
• Channel 4: 10.511.5um
• Channel 5: 11.512.5um
Atmospheric effects
– Depends on spectral transmittance (function of zenith
observation angle)
• Gases
• Aerosols
– Effect in thermal infrared small and neglected
– Exception: volcano eruption
– Correlation exists between the temperature
attenuation due to aerosols and path optical thickness.
Emissivity Effects
• Effect corrected by
linearizing Planck function
around temperature that has
been corrected for the
atmospheric attenuation.
• Calculates the downward
atmospheric temperature
from the downward
atmospheric radiance using
the mean value theorem.
Emissivity Effects
• Radiometric parameter
– Depends on channel
– Depends on temperature
interval
• Emissivity correction
depends on the following:
– Waveband
– Surface emissivity
– Atmospheric profile