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Daytime Land Surface Temperature Extraction from MODIS Thermal Infrared Data under Cirrus Clouds.

Fan X, Tang BH, Wu H, Yan G, Li ZL - Sensors (Basel) (2015)

Bottom Line: The COD was acquired by a look up table of the isolated cirrus bidirectional reflectance at 0.55 μm.Additionally, the slope k of the linear function was expressed as a multiple linear model of the top of the atmospheric brightness temperatures of MODIS channels 31-34 and as the difference between split-window channel emissivities.The simulated data showed that the LST error could be reduced from 11.0 to 2.2 K.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Resources and Environment Information System, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China. fanxw.11b@igsnrr.ac.cn.

ABSTRACT
Simulated data showed that cirrus clouds could lead to a maximum land surface temperature (LST) retrieval error of 11.0 K when using the generalized split-window (GSW) algorithm with a cirrus optical depth (COD) at 0.55 μm of 0.4 and in nadir view. A correction term in the COD linear function was added to the GSW algorithm to extend the GSW algorithm to cirrus cloudy conditions. The COD was acquired by a look up table of the isolated cirrus bidirectional reflectance at 0.55 μm. Additionally, the slope k of the linear function was expressed as a multiple linear model of the top of the atmospheric brightness temperatures of MODIS channels 31-34 and as the difference between split-window channel emissivities. The simulated data showed that the LST error could be reduced from 11.0 to 2.2 K. The sensitivity analysis indicated that the total errors from all the uncertainties of input parameters, extension algorithm accuracy, and GSW algorithm accuracy were less than 2.5 K in nadir view. Finally, the Great Lakes surface water temperatures measured by buoys showed that the retrieval accuracy of the GSW algorithm was improved by at least 1.5 K using the proposed extension algorithm for cirrus skies.

No MeSH data available.


Histograms of (a) COD at 0.55 μm in Figure 9c and (b) LST errors estimated using the proposed extension algorithm (k*COD) in Figure 9d.
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sensors-15-09942-f010: Histograms of (a) COD at 0.55 μm in Figure 9c and (b) LST errors estimated using the proposed extension algorithm (k*COD) in Figure 9d.

Mentions: Figure 10a,b shows the histogram of the COD in Figure 9c and the histogram of the LST errors k*COD in Figure 9d, respectively. Assuming the correction accuracy (the RMSEs are 5.5 and 1.2 K for MOD11_L2 and LSTAC, respectively) of the eight spatially scattered buoys can represent the correction performance of the available pixels in Figure 9d, then it can also be assumed that the clear-sky-based GSW algorithm is commonly misused for the retrieval of LST in cirrus skies with a mean and STD of cirrus COD at 0.55 μm of 0.19 and 0.08, respectively; and as a result, the LSTs are underestimated with the mean and STD of −5.06 and 2.44 K, respectively. Figure 7 indicates that the total LST errors after correction are 1.5 and 2.0 K when VZA = 0° and 60°, respectively, for a COD of 0.2. Hence, LSTs with a mean error of 1.5–2.0 K can be acquired under cirrus cloudy conditions using the proposed extended GSW algorithm.


Daytime Land Surface Temperature Extraction from MODIS Thermal Infrared Data under Cirrus Clouds.

Fan X, Tang BH, Wu H, Yan G, Li ZL - Sensors (Basel) (2015)

Histograms of (a) COD at 0.55 μm in Figure 9c and (b) LST errors estimated using the proposed extension algorithm (k*COD) in Figure 9d.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4481960&req=5

sensors-15-09942-f010: Histograms of (a) COD at 0.55 μm in Figure 9c and (b) LST errors estimated using the proposed extension algorithm (k*COD) in Figure 9d.
Mentions: Figure 10a,b shows the histogram of the COD in Figure 9c and the histogram of the LST errors k*COD in Figure 9d, respectively. Assuming the correction accuracy (the RMSEs are 5.5 and 1.2 K for MOD11_L2 and LSTAC, respectively) of the eight spatially scattered buoys can represent the correction performance of the available pixels in Figure 9d, then it can also be assumed that the clear-sky-based GSW algorithm is commonly misused for the retrieval of LST in cirrus skies with a mean and STD of cirrus COD at 0.55 μm of 0.19 and 0.08, respectively; and as a result, the LSTs are underestimated with the mean and STD of −5.06 and 2.44 K, respectively. Figure 7 indicates that the total LST errors after correction are 1.5 and 2.0 K when VZA = 0° and 60°, respectively, for a COD of 0.2. Hence, LSTs with a mean error of 1.5–2.0 K can be acquired under cirrus cloudy conditions using the proposed extended GSW algorithm.

Bottom Line: The COD was acquired by a look up table of the isolated cirrus bidirectional reflectance at 0.55 μm.Additionally, the slope k of the linear function was expressed as a multiple linear model of the top of the atmospheric brightness temperatures of MODIS channels 31-34 and as the difference between split-window channel emissivities.The simulated data showed that the LST error could be reduced from 11.0 to 2.2 K.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Resources and Environment Information System, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China. fanxw.11b@igsnrr.ac.cn.

ABSTRACT
Simulated data showed that cirrus clouds could lead to a maximum land surface temperature (LST) retrieval error of 11.0 K when using the generalized split-window (GSW) algorithm with a cirrus optical depth (COD) at 0.55 μm of 0.4 and in nadir view. A correction term in the COD linear function was added to the GSW algorithm to extend the GSW algorithm to cirrus cloudy conditions. The COD was acquired by a look up table of the isolated cirrus bidirectional reflectance at 0.55 μm. Additionally, the slope k of the linear function was expressed as a multiple linear model of the top of the atmospheric brightness temperatures of MODIS channels 31-34 and as the difference between split-window channel emissivities. The simulated data showed that the LST error could be reduced from 11.0 to 2.2 K. The sensitivity analysis indicated that the total errors from all the uncertainties of input parameters, extension algorithm accuracy, and GSW algorithm accuracy were less than 2.5 K in nadir view. Finally, the Great Lakes surface water temperatures measured by buoys showed that the retrieval accuracy of the GSW algorithm was improved by at least 1.5 K using the proposed extension algorithm for cirrus skies.

No MeSH data available.