A new method based on lookup tables (LUTs) for retrieval of the ground surface reflectance along coastal zones and islands with MODIS (Moderate-resolution imaging spectroradiometer) image was descibed.Through simulati...A new method based on lookup tables (LUTs) for retrieval of the ground surface reflectance along coastal zones and islands with MODIS (Moderate-resolution imaging spectroradiometer) image was descibed.Through simulation of the AHMAD radiative transfer model, we can retrieve the aerosol optical character with water pixels of MODIS image. Postulating the background is cloudless and the atmosphere on the water is the same as that on the island, we can use the 6S radiative transfer model to compute the LUT about the ground surface reflectance, then use the interpolate method to get the reflectance of the ground surface along coastal zones and islands through the reflectance of the land pixels of MODIS image, the geometric condition and the aerosol optical thickness. The LUT method is applied to determine the ground surface reflectance in Xiamen’s zone from the MODIS image. At last, the results were analyzed and its expectation errors were reported.展开更多
The high spatial resolution and temporal observation frequency of HJ-1/CCD make it suitable for aerosol monitoring.However,because of the lack of a shortwave infrared band,it is difficult to use HJ-1/CCD imagery to re...The high spatial resolution and temporal observation frequency of HJ-1/CCD make it suitable for aerosol monitoring.However,because of the lack of a shortwave infrared band,it is difficult to use HJ-1/CCD imagery to retrieve aerosol optical depth(AOD).We developed a new algorithm for HJ-1/CCD AOD retrieval by introducing MODIS surface reflectance outputs(MOD09) as support.In this algorithm HJ-1/CCD blue band surface reflectance was retrieved through MOD09 blue band surface reflectance by band matching of the two sensors.AOD at 550 nm was then generated through a pre-calculated look-up table for HJ-1/CCD.Eighteen HJ-1/CCD images covering the Jing-Jin-Tang(Beijing-Tianjin-Tangshan) region were used to retrieve AOD using the new algorithm,and the AODs were then validated using AERONET ground measurements in Beijing and Xianghe.The validation shows that compared with AERONET ground measurements,27/29 AODs have error less than 0.1 in absolute value.展开更多
This paper proposed a method to retrieve the land surface reflectance from the HJ-1A/B CCD data. The aerosol optical depth（AOD）, the most important factor affecting the atmospheric correction of CCD images at all ba...This paper proposed a method to retrieve the land surface reflectance from the HJ-1A/B CCD data. The aerosol optical depth（AOD）, the most important factor affecting the atmospheric correction of CCD images at all bands, is proposed to retrieve from the CCD imagery by the approach of dense dark vegetation（DDV） method. A look-up table in terms of the transmittances, the path radiances and the atmospheric spherical albedo as functions of the AOD was established for a variety of sun-sensor geometry and aerosol loadings. The atmospheric correction is then achieved with the look-up table and the MODIS surface reflectance output（MOD09） as the priori datasets. Based on the retrieved AOD and the look-up table of atmospheric correction coefficients, the land surface reflectance was retrieved for the HJ-1A/B data according to the atmospheric radiative transfer equation. Some in-situ measurement Data for Yanzhou of Shandong province in East China and MODIS land surface reflectance products MOD09 are used to preliminarily validate the proposed method. The results show that the proposed method can remove effectively the atmospheric contributions, and the overall accuracy of the retrieval land surface reflectance can be improved substantially.展开更多
Two factors that affect satellite retrieval of Aerosol Optical Depth(AOD) are aerosol model assumptions and the separation of surface reflectance.NASA/MODIS Dense Dark Vegetation(DDV) algorithm has been proven valuabl...Two factors that affect satellite retrieval of Aerosol Optical Depth(AOD) are aerosol model assumptions and the separation of surface reflectance.NASA/MODIS Dense Dark Vegetation(DDV) algorithm has been proven valuable in deriving aerosol distribution and properties over land;however,it cannot be applied to bright targets.As a supplement to the DDV algorithm,an algorithm to retrieve AOD over urban areas in North China in winter is developed using MODIS data,including(1) the generation and analysis of adjacent clear-days surface reflectance using MOD09 product from 2007 to 2008,and(2) seasonal aerosol models derived from AERONET data in Beijing and Xianghe sites.Ground-based measurements using sun photometers were used to validate the retrieved AOD,and the correlation coefficient(r) is up to 0.931.Especially for high AOD values(AOD>0.4),more retrievals meet the inversion accuracy.The temporal variations of retrieval errors over urban,rural and mountain regions were examined,and the results indicated that the variation of blue-band surface reflectance is less than 0.02 in a short period except for unusual weather conditions,the retrieval bias is under 0.08,and the relative error decreases as the AOD increases.展开更多
文摘A new method based on lookup tables (LUTs) for retrieval of the ground surface reflectance along coastal zones and islands with MODIS (Moderate-resolution imaging spectroradiometer) image was descibed.Through simulation of the AHMAD radiative transfer model, we can retrieve the aerosol optical character with water pixels of MODIS image. Postulating the background is cloudless and the atmosphere on the water is the same as that on the island, we can use the 6S radiative transfer model to compute the LUT about the ground surface reflectance, then use the interpolate method to get the reflectance of the ground surface along coastal zones and islands through the reflectance of the land pixels of MODIS image, the geometric condition and the aerosol optical thickness. The LUT method is applied to determine the ground surface reflectance in Xiamen’s zone from the MODIS image. At last, the results were analyzed and its expectation errors were reported.
基金supported by National Natural Science Foundation of China (Grant No.40701112)National Key Technology R & D Program of China (Grant No.2008BAC34B03)National High-tech R & D Program of China (Grant No.2009AA12Z147)
文摘The high spatial resolution and temporal observation frequency of HJ-1/CCD make it suitable for aerosol monitoring.However,because of the lack of a shortwave infrared band,it is difficult to use HJ-1/CCD imagery to retrieve aerosol optical depth(AOD).We developed a new algorithm for HJ-1/CCD AOD retrieval by introducing MODIS surface reflectance outputs(MOD09) as support.In this algorithm HJ-1/CCD blue band surface reflectance was retrieved through MOD09 blue band surface reflectance by band matching of the two sensors.AOD at 550 nm was then generated through a pre-calculated look-up table for HJ-1/CCD.Eighteen HJ-1/CCD images covering the Jing-Jin-Tang(Beijing-Tianjin-Tangshan) region were used to retrieve AOD using the new algorithm,and the AODs were then validated using AERONET ground measurements in Beijing and Xianghe.The validation shows that compared with AERONET ground measurements,27/29 AODs have error less than 0.1 in absolute value.
基金National High Technology Research and Development Program of China,No.2012AA12A302
文摘This paper proposed a method to retrieve the land surface reflectance from the HJ-1A/B CCD data. The aerosol optical depth（AOD）, the most important factor affecting the atmospheric correction of CCD images at all bands, is proposed to retrieve from the CCD imagery by the approach of dense dark vegetation（DDV） method. A look-up table in terms of the transmittances, the path radiances and the atmospheric spherical albedo as functions of the AOD was established for a variety of sun-sensor geometry and aerosol loadings. The atmospheric correction is then achieved with the look-up table and the MODIS surface reflectance output（MOD09） as the priori datasets. Based on the retrieved AOD and the look-up table of atmospheric correction coefficients, the land surface reflectance was retrieved for the HJ-1A/B data according to the atmospheric radiative transfer equation. Some in-situ measurement Data for Yanzhou of Shandong province in East China and MODIS land surface reflectance products MOD09 are used to preliminarily validate the proposed method. The results show that the proposed method can remove effectively the atmospheric contributions, and the overall accuracy of the retrieval land surface reflectance can be improved substantially.
基金supported by National Natural Science Foundation of Chinafor Young Scholar (Grant No. 41101400)National Natural Science Foundation of China for Key Program (Grant No. 41130528)Opening Foundation of State Key Laboratory of Remote Sensing Science ofChina (Grant No. OFSLRSS201103)
文摘Two factors that affect satellite retrieval of Aerosol Optical Depth(AOD) are aerosol model assumptions and the separation of surface reflectance.NASA/MODIS Dense Dark Vegetation(DDV) algorithm has been proven valuable in deriving aerosol distribution and properties over land;however,it cannot be applied to bright targets.As a supplement to the DDV algorithm,an algorithm to retrieve AOD over urban areas in North China in winter is developed using MODIS data,including(1) the generation and analysis of adjacent clear-days surface reflectance using MOD09 product from 2007 to 2008,and(2) seasonal aerosol models derived from AERONET data in Beijing and Xianghe sites.Ground-based measurements using sun photometers were used to validate the retrieved AOD,and the correlation coefficient(r) is up to 0.931.Especially for high AOD values(AOD>0.4),more retrievals meet the inversion accuracy.The temporal variations of retrieval errors over urban,rural and mountain regions were examined,and the results indicated that the variation of blue-band surface reflectance is less than 0.02 in a short period except for unusual weather conditions,the retrieval bias is under 0.08,and the relative error decreases as the AOD increases.
