4.3 Surface Temperature
Infrared radiation is commonly used to remotely determine the global coverage of
surface temperature over the Earth’s surface. However, due to its limitation, the outgoing
infrared radiation from the surface cannot penetrate through clouds to reach the
satellite’s radiometer. Therefore, a cloud-free portion of the scene is used so that land
surface temperature is not mixed with cloud- top temperature. The brightness temperature
retrieved from TIR bands 31 and 32 of TerraMODIS L1B were used to measure the
surface temperature in assumption that the entire object is a perfect blackbody.
Figure 14 Linear regression of surface temperature in TIR bands 31 and 32.
The value
of surface
temperature calculated from TIR bands 31 and 32 is varied
but relatively similar. The relationship between these two bands is linear with 0.9934
coefficient of determination as shown in Figure 14. The value of surface temperature is
varied along with topography where high temperatures are more likely to be identified
in lowlands rather than in highlands as it can be clearly seen from Figure 15. The pattern of
surface temperature will vary depends on the amount of solar radiation absorbed by the
surface. It is related with the physical characteristics of the object. High surface
temperature of an object is generally associated with high emissivity, small heat
capacity, and high thermal conductivity. The rate at which surface temperature decreases
with height is very much affected by adiabatic process. When a parcel of air rises, it moves
into higher altitudes where the surrounding air pressure is lower than on the inside of the air
parcel itself. This pressure difference then causing the air parcel to expands and pushes
on the air around it. Since the work done by air parcel does not gain any heat exchange
Figure 15 The range of surface temperature in the study area K. Table 1 Comparison of statistical approaches in bowtie correction.
Statistics Band 1
Band 3 Band 4
Band 31 Band 32
RMSE 0.00960
0.00575 0.00689
0.15539 0.12670
MAE 0.00598
0.00278 0.00370
0.11067 0.09030
Correlation Coefficient 0.93401
0.92803 0.90951
0.97410 0.97072
K
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