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Oceanography / Meteorology
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Mid-day Atmospheric Humidity from Thermal Infrared Observation of the NOAA-14 AVHRR Satellite: Validation in Tropical Environment
A slope relation between the plot of brightness temperature of channel 4 and 5 of a window array of observation (Fig. 1), centered on each sample site, was compared with the absolute humidity. As the remotely sensed observations record measurement from units of using the observations of relative humidity of find precise relationship with satellite observation. Absolute humidity is a measure of the atmosphere vapor in units of constant calculated from the relative humidity and air temperature measurement (Rosenberg, et al., 1983) observed at meteorological stations. The relationship between the slope of the channel 4 and 5 and absolute humidity were examined.
For estimating atmospheric humidity in temperate region, Goward et al. (1994) employed a window size of 9x9 centered on each sample site. The determination of the appropriate window size depends on the landscape pattern of observation as well as the condition of observation used in this study contain considerable number of cloud free observations are major consideration s for better relationship between TIR observations. Therefore estimations with 9x9 pixels (same as Goward et al., 1994), 24x24 pixels, and 36x6 pixels were compared with ground -observations for all clear sample sites.
Results and Discussion
The comparisons of slope relation of TIR brightens temperature of channels 4 and 5 (Fig.1) in different widow sizes of TIR observation with absolute humidity (Fig.2) calculated to identify the suitable window size of TIR observations in order to estimate the absolute humidity the tropical environment. Further, it reveals that the applications of window size of 9x9 may not be feasible in this study region as it does not have reasonable correlation with absolute humidity measurements (Fig.2). The poor correlation may be due small range of brightness temperature observations acquired for the determination of the slope of TIR observations.
Figure 1. slopes of TIR observation, which is sensitive to the water vapor in the atmosphere, observed to the water vapor in the atmosphere, observed at Supan Buri on November 1, 1995.
Figure 2. Comparison of the of the slope of the relation between the brightness temperatures of channels 4 and 5 in 9x9, 24,24 and 36x36 windows with absolute humidity.
Figure 3. Comparison of the slope of the relation between brightness temperature of channels 4 and 5 and absolute humidity measured at the meteorological observed,
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