Experimental study on directionality in thermal infrared observations of corn canopy

Liu, Q.H.; Liu, Q.; Xin, Xiaozhou; Deng, Rong; Tian, Guo‐Liang; Chen, L.F.; Wang, J.D.; Li, X.W.

doi:10.1109/igarss.2001.976126

Cited by 2 publications

(3 citation statements)

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“…However, surface radiative temperature measured using remote sensors may vary significantly with different view angles, a fact which was discovered as early as in the mid‐1960s [ Fuchs et al , 1967; Monteith and Szeicz , 1962]. Further observations confirmed this angular effect for different surface types [ Balick and Hutchinson , 1986; Balick et al , 1987; Dozier and Warren , 1982; Lagouarde et al , 1995, 2000, 2004; Liu et al , 2000, 2001; McAtee et al , 2003; Menenti et al , 2001; Parsons , 1985; Paw U et al , 1989; Smith et al , 1997b]. According to the experimental results presented by Paw U [1992], the directional radiative temperature of row crop canopies can vary up to 13 K, thus it is not possible to evaluate surface fluxes accurately using a single directional surface radiative temperature measured by remote sensors.…”

Section: Introductionmentioning

confidence: 84%

“…The azimuth angle step was set to be 30° and it took about 20 min to complete one set of directional observations, during which the component temperature would change slightly. A correction method was applied to remove the temporal effect adapted from Liu et al [2001]. That is, the mean T B (0) was first calculated from all profiles.…”

Section: Experimental Setup and Data Preprocessingmentioning

confidence: 99%

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Temporal patterns of thermal emission directionality of crop canopies

et al. 2011

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[1] Many field experiments have observed significant temporal variations of thermal infrared (TIR) emission directionality, making it necessary to explain this phenomenon quantitatively to exploit potential applications of the directional remotely sensed TIR observation. The main objective of this paper is to determine when and how the significant directional effect appears. Two models, TRGM and Cupid, are linked to simulate the temporal variations of directional brightness temperature T B ( ) of crop canopies, including winter wheat and summer corn. Two indicators are defined: (1) DT B,AVG representing the mean difference between nadir T B (0) and off-nadir T B (55) and (2) DT B,STD representing the standard deviation of T B (55) for different view azimuth angles. Simulation results show that the highest DT B,AVG of up to 4°C appears mostly at midday (1200-1300 LT), while the lowest DT B,AVG appears mostly in the early morning (0700-0800 LT) or late afternoon (1700-1800 LT). The DT B,STD is about one third of DT B,AVG and should not be neglected given its considerable value at around 1400 LT. This trend has been proven through field measurements at both wheat and corn sites. The major factors affecting the trend are also identified using sensitivity analysis. Among the major factors, soil water content, LAI, and solar radiation are the three most significant factors, whereas the wind speed and air temperature have a larger effect on DT B,AVG than air humidity. It is interesting that DT B,AVG reaches a maximum value when the LAI is around 0.8. Further analysis shows that DT B,AVG is related to soil surface net radiation, which will be useful in net radiation estimation.

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Section: Introductionmentioning

confidence: 84%

Section: Experimental Setup and Data Preprocessingmentioning

confidence: 99%

Temporal patterns of thermal emission directionality of crop canopies

et al. 2011

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“…Extensive ground-based multiangular TIR measurements have been carried out for theoretical research purposes (Liu et al, 2001;Menenti et al, 2001;Sobrino et al, 2005). Using multiangular observations and physics-based models, the retrieval of component temperature becomes possible, which bears more physical meaning than the pixel-average temperature and provides better parameterization of heat flux at the landatmosphere interface (Jia, 2004;Xu et al, 2001).…”

Section: Introductionmentioning

confidence: 99%