Abstract
In order to modeling directional thermal radiation and energy balance for a partially covered canopy, surface brightness temperature is usually classified into several components. This paper researches the methodology for brightness temperature component classification and temporal variations of component number and values by an in situ experiment, dedicated to analyze maize canopy brightness temperature distribution. The measurement was carried out by using a TIR camera and a visible camera mounted on an industrial crane, the experiment lasted 3 months throughout a maize growth cycle. In the analysis of the brightness temperature, a Gaussian distribution has been assumed. Results show the number of components and their brightness temperature values vary with time of day and biomass density. Three brightness temperature components of vegetation, sunlit and shaded soil could be identified at midday during the measurement period. In the daytime, temperature variability of sunlit soil is much larger than the other two components when the canopy's density is not high. When the canopy is fully covered, vegetation brightness temperature has a wider range.
Highlights
As one of physical parameters directly provided by remote observations, surface brightness temperature has been widely used to study energy budget of agricultural fields for determining canopy evapotranspiration, water stress, soil moisture, vegetation growing status
Being a solution in the modeling of energy budget and directional variations of emitted thermal radiation, surface brightness temperature is usually classified into several temperature components
In order to describe the distribution of canopy surface brightness temperature, various methodologies have been utilised for brightness temperature component classification, which were defined by temperature values, canopy components or combination of these two factors
Summary
As one of physical parameters directly provided by remote observations, surface brightness temperature has been widely used to study energy budget of agricultural fields for determining canopy evapotranspiration, water stress, soil moisture, vegetation growing status. Being a solution in the modeling of energy budget and directional variations of emitted thermal radiation, surface brightness temperature is usually classified into several temperature components. Many researchers revealed that brightness temperature components had temporal variations. In two experiments over cotton canopy, Kimes et al and Kustas et al [1, 2] showed sunlit soil temperature changed up to 30°C during the measuring day from the morning to the afternoon, shaded soil temperature generally follow the temporal trend of sunlit soil temperature with a 20°C amplitude, vegetation’s brightness temperature varied within 10°C
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