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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.


Related in: MedlinePlus

RMSEs between the LSTclear-sky and LSTCOD (hollow symbols) and the RMSEs between the LSTclear-sky and LSTAC (solid symbols) for three VZAs. LSTCOD and LSTclear-sky are those retrieved from Data-cirrus and Data-clearsky using the GSW algorithm, respectively. LSTAC are the LSTs of LSTCOD minus the correction term k*COD.
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sensors-15-09942-f005: RMSEs between the LSTclear-sky and LSTCOD (hollow symbols) and the RMSEs between the LSTclear-sky and LSTAC (solid symbols) for three VZAs. LSTCOD and LSTclear-sky are those retrieved from Data-cirrus and Data-clearsky using the GSW algorithm, respectively. LSTAC are the LSTs of LSTCOD minus the correction term k*COD.

Mentions: Using the COD that can be interpolated from the ICBR LUT in actual applications, and with the slope k determined from TOA brightness temperatures in MODIS channels 31–34 and split-window channel emissivities, the LST retrieve accuracy of the GSW algorithm under cirrus skies is improved using the correction term LSTCOD − k*COD = LSTAC. Figure 5 shows the RMSEs between the LSTCOD and LSTclear-sky (hollow symbols) and the RMSEs between the LSTAC and LSTclear-sky (solid symbols). The RMSE is 1.2 K with a COD of 0.04 and a VZA of 0°, increasing to 13.4 K with a COD of 0.4 and a VZA of 60° without correction. Figure 5 also indicates that the RMSE increases slightly with increasing VZA and COD after correction; the maximum RMSE between LSTAC and LSTclear-sky is 3.2 K when the COD at 0.55 μm is 0.4 and a VZA of 60°.


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)

RMSEs between the LSTclear-sky and LSTCOD (hollow symbols) and the RMSEs between the LSTclear-sky and LSTAC (solid symbols) for three VZAs. LSTCOD and LSTclear-sky are those retrieved from Data-cirrus and Data-clearsky using the GSW algorithm, respectively. LSTAC are the LSTs of LSTCOD minus the correction term k*COD.
© Copyright Policy
Related In: Results  -  Collection

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

sensors-15-09942-f005: RMSEs between the LSTclear-sky and LSTCOD (hollow symbols) and the RMSEs between the LSTclear-sky and LSTAC (solid symbols) for three VZAs. LSTCOD and LSTclear-sky are those retrieved from Data-cirrus and Data-clearsky using the GSW algorithm, respectively. LSTAC are the LSTs of LSTCOD minus the correction term k*COD.
Mentions: Using the COD that can be interpolated from the ICBR LUT in actual applications, and with the slope k determined from TOA brightness temperatures in MODIS channels 31–34 and split-window channel emissivities, the LST retrieve accuracy of the GSW algorithm under cirrus skies is improved using the correction term LSTCOD − k*COD = LSTAC. Figure 5 shows the RMSEs between the LSTCOD and LSTclear-sky (hollow symbols) and the RMSEs between the LSTAC and LSTclear-sky (solid symbols). The RMSE is 1.2 K with a COD of 0.04 and a VZA of 0°, increasing to 13.4 K with a COD of 0.4 and a VZA of 60° without correction. Figure 5 also indicates that the RMSE increases slightly with increasing VZA and COD after correction; the maximum RMSE between LSTAC and LSTclear-sky is 3.2 K when the COD at 0.55 μm is 0.4 and a VZA of 60°.

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.


Related in: MedlinePlus