The Experts below are selected from a list of 279 Experts worldwide ranked by ideXlab platform
L. T. Molina - One of the best experts on this subject based on the ideXlab platform.
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Analysis of Visible/SWIR surface reflectance ratios for aerosol retrievals from satellite in Mexico City urban area
Atmospheric Chemistry and Physics, 2007Co-Authors: A. D. De Almeida Castanho, R. Prinn, V. Martins, M. Herold, C. Ichoku, L. T. MolinaAbstract:The surface reflectance ratio between the visible (VIS) and shortwave infrared (SWIR) radiation is an important quantity for the retrieval of the aerosol optical depth (?a) from the MODIS sensor data. Based on empirically determined VIS/SWIR ratios, MODIS ?a retrieval uses the surface reflectance in the SWIR band (2.1 µm), where the interaction between solar radiation and the aerosol layer is small, to predict the visible reflectances in the blue (0.47 µm) and red (0.66 µm) bands. Therefore, accurate knowledge of the VIS/SWIR ratio is essential for achieving accurate retrieval of aerosol optical depth from MODIS. We analyzed the surface reflectance over some distinct surface covers in and around the Mexico City metropolitan area (MCMA) using MODIS radiances at 0.66 µm and 2.1 µm. The analysis was performed at 1.5 km×1.5 km spatial resolution. Also, ground-based AERONET sun-Photometer data acquired in Mexico City from 2002 to 2005 were analyzed for aerosol depth and other aerosol optical properties. In addition, a network of hand-held sun-Photometers deployed in Mexico City, as part of the MCMA-2006 Study during the MILAGRO Campaign, provided an unprecedented measurement of ?a in 5 different sites well distributed in the city. We found that the average RED/SWIR ratio representative of the urbanized sites analyzed is 0.73±0.06 for scattering angles
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Urban Visible/SWIR surface reflectance ratios from satellite and sun Photometer measurements in Mexico City
Atmospheric Chemistry and Physics Discussions, 2007Co-Authors: A. D. De Almeida Castanho, R. Prinn, V. Martins, M. Herold, C. Ichoku, L. T. MolinaAbstract:The surface reflectance ratio between the visible (VIS) and shortwave infrared (SWIR) radiation is an important quantity for the retrieval of the aerosol optical depth (?a) from the MODIS sensor data. Based on empirically determined VIS/SWIR ratios, MODIS ?a retrieval uses the surface reflectance in the SWIR band (2.1 ?m), where the interaction between solar radiation and the aerosol layer is small, to predict the visible reflectances in the blue (0.47 ?m) and red (0.66 ?m) bands. Therefore, accurate knowledge of the VIS/SWIR ratio is essential for achieving accurate retrieval of aerosol optical depth from MODIS. The heterogeneity of the surface cover in an urban environment increases the uncertainties in the estimation of the surface reflectance and, consequently, ?a. We analyzed the surface reflectance over some distinct surface covers in and around the Mexico City metropolitan area (MCMA) using MODIS radiances at 0.66 ?m and 2.1 ?m. The analysis was performed at 1.5 km×1.5 km spatial resolution. Also, ground-based AERONET sun-Photometer data acquired in Mexico City from 2002 to 2005 were analyzed for aerosol optical thickness and other aerosol optical properties. In addition, a network of hand-held sun-Photometers deployed in Mexico City, as part of the MCMA-2006 Study during the MILAGRO Campaign, provided an unprecedented measurement of ?a in 5 different sites well distributed in the city. We found that the average RED/SWIR ratio representative of the urbanized sites analyzed is 0.73±0.06. This average ratio was significantly different for non-urban sites, which was approximately 0.55. The aerosol optical thickness retrieved from MODIS radiances at a spatial resolution of 1.5 km×1.5 km and averaged within 10 x 10 km boxes were compared with collocated 1-h ?a averaged from sun-Photometer measurements. The use of the new RED/SWIR ratio of 0.73 in the MODIS retrieval led to a significant improvement in the agreement between the MODIS and sun-Photometer results; with the slope, offset, and the correlation coefficient of the linear regression changing from (?aMODIS = 0.91 ?a sun-Photometer + 0.33 ,R2=0.66) to (?aMODIS = 0.96 ?a sun-Photometer ?0.006, R2=0.87).
A. D. De Almeida Castanho - One of the best experts on this subject based on the ideXlab platform.
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Analysis of Visible/SWIR surface reflectance ratios for aerosol retrievals from satellite in Mexico City urban area
Atmospheric Chemistry and Physics, 2007Co-Authors: A. D. De Almeida Castanho, R. Prinn, V. Martins, M. Herold, C. Ichoku, L. T. MolinaAbstract:The surface reflectance ratio between the visible (VIS) and shortwave infrared (SWIR) radiation is an important quantity for the retrieval of the aerosol optical depth (?a) from the MODIS sensor data. Based on empirically determined VIS/SWIR ratios, MODIS ?a retrieval uses the surface reflectance in the SWIR band (2.1 µm), where the interaction between solar radiation and the aerosol layer is small, to predict the visible reflectances in the blue (0.47 µm) and red (0.66 µm) bands. Therefore, accurate knowledge of the VIS/SWIR ratio is essential for achieving accurate retrieval of aerosol optical depth from MODIS. We analyzed the surface reflectance over some distinct surface covers in and around the Mexico City metropolitan area (MCMA) using MODIS radiances at 0.66 µm and 2.1 µm. The analysis was performed at 1.5 km×1.5 km spatial resolution. Also, ground-based AERONET sun-Photometer data acquired in Mexico City from 2002 to 2005 were analyzed for aerosol depth and other aerosol optical properties. In addition, a network of hand-held sun-Photometers deployed in Mexico City, as part of the MCMA-2006 Study during the MILAGRO Campaign, provided an unprecedented measurement of ?a in 5 different sites well distributed in the city. We found that the average RED/SWIR ratio representative of the urbanized sites analyzed is 0.73±0.06 for scattering angles
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Urban Visible/SWIR surface reflectance ratios from satellite and sun Photometer measurements in Mexico City
Atmospheric Chemistry and Physics Discussions, 2007Co-Authors: A. D. De Almeida Castanho, R. Prinn, V. Martins, M. Herold, C. Ichoku, L. T. MolinaAbstract:The surface reflectance ratio between the visible (VIS) and shortwave infrared (SWIR) radiation is an important quantity for the retrieval of the aerosol optical depth (?a) from the MODIS sensor data. Based on empirically determined VIS/SWIR ratios, MODIS ?a retrieval uses the surface reflectance in the SWIR band (2.1 ?m), where the interaction between solar radiation and the aerosol layer is small, to predict the visible reflectances in the blue (0.47 ?m) and red (0.66 ?m) bands. Therefore, accurate knowledge of the VIS/SWIR ratio is essential for achieving accurate retrieval of aerosol optical depth from MODIS. The heterogeneity of the surface cover in an urban environment increases the uncertainties in the estimation of the surface reflectance and, consequently, ?a. We analyzed the surface reflectance over some distinct surface covers in and around the Mexico City metropolitan area (MCMA) using MODIS radiances at 0.66 ?m and 2.1 ?m. The analysis was performed at 1.5 km×1.5 km spatial resolution. Also, ground-based AERONET sun-Photometer data acquired in Mexico City from 2002 to 2005 were analyzed for aerosol optical thickness and other aerosol optical properties. In addition, a network of hand-held sun-Photometers deployed in Mexico City, as part of the MCMA-2006 Study during the MILAGRO Campaign, provided an unprecedented measurement of ?a in 5 different sites well distributed in the city. We found that the average RED/SWIR ratio representative of the urbanized sites analyzed is 0.73±0.06. This average ratio was significantly different for non-urban sites, which was approximately 0.55. The aerosol optical thickness retrieved from MODIS radiances at a spatial resolution of 1.5 km×1.5 km and averaged within 10 x 10 km boxes were compared with collocated 1-h ?a averaged from sun-Photometer measurements. The use of the new RED/SWIR ratio of 0.73 in the MODIS retrieval led to a significant improvement in the agreement between the MODIS and sun-Photometer results; with the slope, offset, and the correlation coefficient of the linear regression changing from (?aMODIS = 0.91 ?a sun-Photometer + 0.33 ,R2=0.66) to (?aMODIS = 0.96 ?a sun-Photometer ?0.006, R2=0.87).
C. Ichoku - One of the best experts on this subject based on the ideXlab platform.
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Analysis of Visible/SWIR surface reflectance ratios for aerosol retrievals from satellite in Mexico City urban area
Atmospheric Chemistry and Physics, 2007Co-Authors: A. D. De Almeida Castanho, R. Prinn, V. Martins, M. Herold, C. Ichoku, L. T. MolinaAbstract:The surface reflectance ratio between the visible (VIS) and shortwave infrared (SWIR) radiation is an important quantity for the retrieval of the aerosol optical depth (?a) from the MODIS sensor data. Based on empirically determined VIS/SWIR ratios, MODIS ?a retrieval uses the surface reflectance in the SWIR band (2.1 µm), where the interaction between solar radiation and the aerosol layer is small, to predict the visible reflectances in the blue (0.47 µm) and red (0.66 µm) bands. Therefore, accurate knowledge of the VIS/SWIR ratio is essential for achieving accurate retrieval of aerosol optical depth from MODIS. We analyzed the surface reflectance over some distinct surface covers in and around the Mexico City metropolitan area (MCMA) using MODIS radiances at 0.66 µm and 2.1 µm. The analysis was performed at 1.5 km×1.5 km spatial resolution. Also, ground-based AERONET sun-Photometer data acquired in Mexico City from 2002 to 2005 were analyzed for aerosol depth and other aerosol optical properties. In addition, a network of hand-held sun-Photometers deployed in Mexico City, as part of the MCMA-2006 Study during the MILAGRO Campaign, provided an unprecedented measurement of ?a in 5 different sites well distributed in the city. We found that the average RED/SWIR ratio representative of the urbanized sites analyzed is 0.73±0.06 for scattering angles
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Urban Visible/SWIR surface reflectance ratios from satellite and sun Photometer measurements in Mexico City
Atmospheric Chemistry and Physics Discussions, 2007Co-Authors: A. D. De Almeida Castanho, R. Prinn, V. Martins, M. Herold, C. Ichoku, L. T. MolinaAbstract:The surface reflectance ratio between the visible (VIS) and shortwave infrared (SWIR) radiation is an important quantity for the retrieval of the aerosol optical depth (?a) from the MODIS sensor data. Based on empirically determined VIS/SWIR ratios, MODIS ?a retrieval uses the surface reflectance in the SWIR band (2.1 ?m), where the interaction between solar radiation and the aerosol layer is small, to predict the visible reflectances in the blue (0.47 ?m) and red (0.66 ?m) bands. Therefore, accurate knowledge of the VIS/SWIR ratio is essential for achieving accurate retrieval of aerosol optical depth from MODIS. The heterogeneity of the surface cover in an urban environment increases the uncertainties in the estimation of the surface reflectance and, consequently, ?a. We analyzed the surface reflectance over some distinct surface covers in and around the Mexico City metropolitan area (MCMA) using MODIS radiances at 0.66 ?m and 2.1 ?m. The analysis was performed at 1.5 km×1.5 km spatial resolution. Also, ground-based AERONET sun-Photometer data acquired in Mexico City from 2002 to 2005 were analyzed for aerosol optical thickness and other aerosol optical properties. In addition, a network of hand-held sun-Photometers deployed in Mexico City, as part of the MCMA-2006 Study during the MILAGRO Campaign, provided an unprecedented measurement of ?a in 5 different sites well distributed in the city. We found that the average RED/SWIR ratio representative of the urbanized sites analyzed is 0.73±0.06. This average ratio was significantly different for non-urban sites, which was approximately 0.55. The aerosol optical thickness retrieved from MODIS radiances at a spatial resolution of 1.5 km×1.5 km and averaged within 10 x 10 km boxes were compared with collocated 1-h ?a averaged from sun-Photometer measurements. The use of the new RED/SWIR ratio of 0.73 in the MODIS retrieval led to a significant improvement in the agreement between the MODIS and sun-Photometer results; with the slope, offset, and the correlation coefficient of the linear regression changing from (?aMODIS = 0.91 ?a sun-Photometer + 0.33 ,R2=0.66) to (?aMODIS = 0.96 ?a sun-Photometer ?0.006, R2=0.87).
M. Herold - One of the best experts on this subject based on the ideXlab platform.
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Analysis of Visible/SWIR surface reflectance ratios for aerosol retrievals from satellite in Mexico City urban area
Atmospheric Chemistry and Physics, 2007Co-Authors: A. D. De Almeida Castanho, R. Prinn, V. Martins, M. Herold, C. Ichoku, L. T. MolinaAbstract:The surface reflectance ratio between the visible (VIS) and shortwave infrared (SWIR) radiation is an important quantity for the retrieval of the aerosol optical depth (?a) from the MODIS sensor data. Based on empirically determined VIS/SWIR ratios, MODIS ?a retrieval uses the surface reflectance in the SWIR band (2.1 µm), where the interaction between solar radiation and the aerosol layer is small, to predict the visible reflectances in the blue (0.47 µm) and red (0.66 µm) bands. Therefore, accurate knowledge of the VIS/SWIR ratio is essential for achieving accurate retrieval of aerosol optical depth from MODIS. We analyzed the surface reflectance over some distinct surface covers in and around the Mexico City metropolitan area (MCMA) using MODIS radiances at 0.66 µm and 2.1 µm. The analysis was performed at 1.5 km×1.5 km spatial resolution. Also, ground-based AERONET sun-Photometer data acquired in Mexico City from 2002 to 2005 were analyzed for aerosol depth and other aerosol optical properties. In addition, a network of hand-held sun-Photometers deployed in Mexico City, as part of the MCMA-2006 Study during the MILAGRO Campaign, provided an unprecedented measurement of ?a in 5 different sites well distributed in the city. We found that the average RED/SWIR ratio representative of the urbanized sites analyzed is 0.73±0.06 for scattering angles
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Urban Visible/SWIR surface reflectance ratios from satellite and sun Photometer measurements in Mexico City
Atmospheric Chemistry and Physics Discussions, 2007Co-Authors: A. D. De Almeida Castanho, R. Prinn, V. Martins, M. Herold, C. Ichoku, L. T. MolinaAbstract:The surface reflectance ratio between the visible (VIS) and shortwave infrared (SWIR) radiation is an important quantity for the retrieval of the aerosol optical depth (?a) from the MODIS sensor data. Based on empirically determined VIS/SWIR ratios, MODIS ?a retrieval uses the surface reflectance in the SWIR band (2.1 ?m), where the interaction between solar radiation and the aerosol layer is small, to predict the visible reflectances in the blue (0.47 ?m) and red (0.66 ?m) bands. Therefore, accurate knowledge of the VIS/SWIR ratio is essential for achieving accurate retrieval of aerosol optical depth from MODIS. The heterogeneity of the surface cover in an urban environment increases the uncertainties in the estimation of the surface reflectance and, consequently, ?a. We analyzed the surface reflectance over some distinct surface covers in and around the Mexico City metropolitan area (MCMA) using MODIS radiances at 0.66 ?m and 2.1 ?m. The analysis was performed at 1.5 km×1.5 km spatial resolution. Also, ground-based AERONET sun-Photometer data acquired in Mexico City from 2002 to 2005 were analyzed for aerosol optical thickness and other aerosol optical properties. In addition, a network of hand-held sun-Photometers deployed in Mexico City, as part of the MCMA-2006 Study during the MILAGRO Campaign, provided an unprecedented measurement of ?a in 5 different sites well distributed in the city. We found that the average RED/SWIR ratio representative of the urbanized sites analyzed is 0.73±0.06. This average ratio was significantly different for non-urban sites, which was approximately 0.55. The aerosol optical thickness retrieved from MODIS radiances at a spatial resolution of 1.5 km×1.5 km and averaged within 10 x 10 km boxes were compared with collocated 1-h ?a averaged from sun-Photometer measurements. The use of the new RED/SWIR ratio of 0.73 in the MODIS retrieval led to a significant improvement in the agreement between the MODIS and sun-Photometer results; with the slope, offset, and the correlation coefficient of the linear regression changing from (?aMODIS = 0.91 ?a sun-Photometer + 0.33 ,R2=0.66) to (?aMODIS = 0.96 ?a sun-Photometer ?0.006, R2=0.87).
V. Martins - One of the best experts on this subject based on the ideXlab platform.
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Analysis of Visible/SWIR surface reflectance ratios for aerosol retrievals from satellite in Mexico City urban area
Atmospheric Chemistry and Physics, 2007Co-Authors: A. D. De Almeida Castanho, R. Prinn, V. Martins, M. Herold, C. Ichoku, L. T. MolinaAbstract:The surface reflectance ratio between the visible (VIS) and shortwave infrared (SWIR) radiation is an important quantity for the retrieval of the aerosol optical depth (?a) from the MODIS sensor data. Based on empirically determined VIS/SWIR ratios, MODIS ?a retrieval uses the surface reflectance in the SWIR band (2.1 µm), where the interaction between solar radiation and the aerosol layer is small, to predict the visible reflectances in the blue (0.47 µm) and red (0.66 µm) bands. Therefore, accurate knowledge of the VIS/SWIR ratio is essential for achieving accurate retrieval of aerosol optical depth from MODIS. We analyzed the surface reflectance over some distinct surface covers in and around the Mexico City metropolitan area (MCMA) using MODIS radiances at 0.66 µm and 2.1 µm. The analysis was performed at 1.5 km×1.5 km spatial resolution. Also, ground-based AERONET sun-Photometer data acquired in Mexico City from 2002 to 2005 were analyzed for aerosol depth and other aerosol optical properties. In addition, a network of hand-held sun-Photometers deployed in Mexico City, as part of the MCMA-2006 Study during the MILAGRO Campaign, provided an unprecedented measurement of ?a in 5 different sites well distributed in the city. We found that the average RED/SWIR ratio representative of the urbanized sites analyzed is 0.73±0.06 for scattering angles
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Urban Visible/SWIR surface reflectance ratios from satellite and sun Photometer measurements in Mexico City
Atmospheric Chemistry and Physics Discussions, 2007Co-Authors: A. D. De Almeida Castanho, R. Prinn, V. Martins, M. Herold, C. Ichoku, L. T. MolinaAbstract:The surface reflectance ratio between the visible (VIS) and shortwave infrared (SWIR) radiation is an important quantity for the retrieval of the aerosol optical depth (?a) from the MODIS sensor data. Based on empirically determined VIS/SWIR ratios, MODIS ?a retrieval uses the surface reflectance in the SWIR band (2.1 ?m), where the interaction between solar radiation and the aerosol layer is small, to predict the visible reflectances in the blue (0.47 ?m) and red (0.66 ?m) bands. Therefore, accurate knowledge of the VIS/SWIR ratio is essential for achieving accurate retrieval of aerosol optical depth from MODIS. The heterogeneity of the surface cover in an urban environment increases the uncertainties in the estimation of the surface reflectance and, consequently, ?a. We analyzed the surface reflectance over some distinct surface covers in and around the Mexico City metropolitan area (MCMA) using MODIS radiances at 0.66 ?m and 2.1 ?m. The analysis was performed at 1.5 km×1.5 km spatial resolution. Also, ground-based AERONET sun-Photometer data acquired in Mexico City from 2002 to 2005 were analyzed for aerosol optical thickness and other aerosol optical properties. In addition, a network of hand-held sun-Photometers deployed in Mexico City, as part of the MCMA-2006 Study during the MILAGRO Campaign, provided an unprecedented measurement of ?a in 5 different sites well distributed in the city. We found that the average RED/SWIR ratio representative of the urbanized sites analyzed is 0.73±0.06. This average ratio was significantly different for non-urban sites, which was approximately 0.55. The aerosol optical thickness retrieved from MODIS radiances at a spatial resolution of 1.5 km×1.5 km and averaged within 10 x 10 km boxes were compared with collocated 1-h ?a averaged from sun-Photometer measurements. The use of the new RED/SWIR ratio of 0.73 in the MODIS retrieval led to a significant improvement in the agreement between the MODIS and sun-Photometer results; with the slope, offset, and the correlation coefficient of the linear regression changing from (?aMODIS = 0.91 ?a sun-Photometer + 0.33 ,R2=0.66) to (?aMODIS = 0.96 ?a sun-Photometer ?0.006, R2=0.87).
