UCSB Emissivity Library
Welcome to the MODIS
(Moderate Resolution Imaging Spectrometer)
UCSB Emissivity Library.
This library is a collection of Emissivity
measurements of natural and manmade materials
that may be used as a source of spectral emissivities at the component level
in the TIR BRDF models to calculate the scene emissivities in the split-window
channels to be used in the LST algorithms.
This data set was collected by Dr. Zhengming Wan's Group
(Institute for Computational Earth System Science) located on the campus
of UCSB (University of California, Santa
What is the Emissivity Library
Measurements in Laboratory
The Emissivity Library is used to characterize the spectral
features and ranges of the emissivities of terrestrial natural and manmade
It can be also used as a source of the spectral emissivities
for the components in the MODIS scene to calculate the classification-based
emissivities in the split-window channels with TIR BRDF models.
Then the classification-based emissivities can be used in the split-window
Kinds of materials in this library
The emissivity of flat materials is usually determined by
measuring their reflectance with a TIR spectrometer combined with an
integrating sphere and converting the reflectance to directional-hemispherical
emissivity by the use of Kirchhoff's law.
ice, and snow generally have a high emissivity, 0.94 to 0.99, across
the thermal infrared region. Snow is unusual in that it has a high reflectance
in the solar (visible) region where most of the downwelling energy is during
the day, and a very high emissivity in the thermal region.
and Minerals exhibit stronger spectral features. The "restralen"
bands of quartz sand cause strong spectral features between 8 and 10 microns
that depend on the grain size. The signature in the 3 to 5 µm region
depends strongly on the water and organic content. The dryer, purer soils
have lower emissivities in this region.
Green vegetation typically has a very high emissivity because it is structured
and contains water. Senescent (dry) vegetation has a more variable emissivity,
especially in the 3 to 5 µm region, which depends on the type and
structure of the cover type, the dryness, and so forth.
materials such as refined, polished metals have among the lowest
emissivity values. That of polished metals can be made less than 0.01 (better
than 99% reflecting) and, for this reason, are good for use in thermal
infrared optical systems. Rough dielectric materials such as asphalt and
brick are in the same range as natural materials, approximately 0.90 to
0.98. This group also contains miscellaneous items such as painted
aluminum fixtures, a plastic box top, and a computer disk surface.
Developed by: Yulin Zhang
Last revised: November 10, 1999