Biomedical Engineering Reference
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shows similar distribution in both the seasons. On the other hand, LST decreases, in
general, with increasing density of vegetated areas. Hence, the study reveals that
emissivity of surface cover and vegetation density has strong influence on LST
retrieval and needs to be studied vis-à-vis intrinsic soil properties, vegetation, and
atmosphere condition. It would help to thermally characterize different land cover
types, the convective flow, and effect on biophysical processes.
Keywords Landsat ETM+
LST
Landuse
Vegetation density
Emissivity
Heat island
Introduction
Land surface temperature (LST) is one of the important factor controlling most of
the physical, chemical, and biological processes on the Earth. LST is controlled by a
large number of land surface and atmospheric phenomena viz., surface energy
balance, atmospheric state, thermal properties of surface, and subsurface mediums
in conjunction with sensor calibration parameters. Hence, understanding the com-
plex interaction of thermal energy with each of these components is utmost
important to model the actual ground temperature. The approximated LST after
atmospheric, sensor, and emissivity correction serves as important parameter for
land surface characterization, energy budgeting, and global circulation pattern in
global scale. A large number of on board sensors with varying resolution and
thermal bands are available for modeling various Earth processes but the challenge
remains in retrieval of précised ground temperature from at-sensor brightness
temperature. As the outgoing long wave thermal radiation while passing through the
atmosphere interacts with water vapor and aerosols, and the return signals gets
attenuated due to atmospheric water vapor absorption or gets scattered due to
aerosols. Hence, sensing of LST from space platform required rigorous calibration
for interfering components of atmosphere. Besides atmosphere intrinsic surface
properties and surface vegetation cover also modifies the ground radiance due to
differential thermal inertia of land cover complex which consists of materials, water,
vegetation, etc. In the present study, major emphasis was given to understand how
different land cover types and vegetation density affect LST seasonally along with
thermal characterization of different land cover complexes. Effort has been made to
validate the satellite derived LST with limited ground measured temperature.
Study Area
The study area consists of two Rayons (district) of western Oblast (state) of
Republic of Kazakhstan (Fig.
1
). The Rayons are Chingarlausky and Karatobinsky
occupying area of 17,105 km
2
. The landform is predominantly marine and littoral
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