Geoscience Reference
In-Depth Information
3.2 Land Surface Temperature (LST) Retrieval
The mono-window algorithm method as utilized by Qin et al. (
2001
) is used to
generate the Land Surface Temperature (LST) map. The mono-window algorithm
requires three parameters; emissivity, transmittance and effective mean atmo-
spheric temperature (Sobrino et al.
2004
). The atmospheric water vapour content
and the near surface air temperature are used to calculate the air transmittance and
effective mean atmospheric temperature (Liu and Zhang
2011
). The third
parameter is emissivity, which is calculated from the normalized difference veg-
etation index (NDVI). The mono-window algorithm is given as:
T
s
¼ a1
C
D
f
ð
Þ þ
b1
C
D
½
ð
Þ þ
C
þ
D
T
i
DTa
g
=
C
ð
1
Þ
where Ts is LST in Kelvin; a =-67.355351; b = 0.458606; (C = T
i
9 T
a;
where
T
i
= emissivity can be computed from NDVI); D = (1-T
a
)[1? (1-T
i
) 9 T
a
];
Ti is the brightness temperature (K) and T
a
is the effective mean atmospheric
temperature.
3.3 Generation of Normalized Difference Vegetation Index
Maps
GIS spatial analysis and zonal statistical analysis technique are used to visualize
the vegetation fragmentation and surface temperature distribution. Equation
2
is
used to calculate the NDVI of the study area. The proposed emissivity values from
different NDVI range; i.e. NDVI \ 0.2 (bare soil), 0.2 \ NDVI \ 0.5 (mixture of
bare soil, vegetation and hard surfaces) and NDVI [ 0.5 (fully vegetated) are 0.99,
0.98 and 0.98 respectively
NDVI ¼ NIR
R
ð
Þ
=
NIR
þ
R
ð
Þ
ð
2
Þ
where
NIR—the pixel digital number (DN) of TM Band 4
R—DN of TM Band 3
3.4 Spatial Analysis
The spatial analysis stage involves the generation of transaction profiles of the
surface temperature and NDVI value across detailed studies area for the year 2009.
The process of extracting profiles is carried out in the ArcGIS software.
