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Radiometric Cross-Calibration of Tiangong-2 MWI Visible/NIR Channels over Aquatic Environments using MODIS
摘要： The Moderate-Resolution Wide-Wavelength Imager (MWI), onboard the Tiangong-2 (TG-2) Space Lab, is an experimental satellite sensor designed for the next-generation Chinese ocean color satellites. The MWI imagery is not sufficiently radiometrically calibrated, and therefore, the cross-calibration is urgently needed to provide high quality ocean color products for MWI observations. We proposed a simple and effective cross-calibration scheme for MWI data using well calibrated Moderate Resolution Imaging Spectroradiometer (MODIS) imagery over aquatic environments. The path radiance of the MWI was estimated using the quasi-synchronized MODIS images as well as the MODIS Rayleigh and aerosol look up tables (LUTs) from SeaWiFS Data Analysis System 7.4 (SeaDAS 7.4). The results showed that the coefficients of determination (R2) of the calibration coefficients were larger than 0.97, with sufficient matched areas to perform cross-calibration for MWI. Compared with the simulated Top of Atmosphere (TOA) radiance using synchronized MODIS images, all errors calculated with the calibration coefficients retrieved in this paper were less than 5.2%, and lower than the lab calibrated coefficients. The Rayleigh-corrected reflectance (ρrc), remote sensing reflectance (Rrs) and total suspended matter (TSM) products of MWI, MODIS and the Geostationary Ocean Color Imager (GOCI) images for Taihu Lake in China were compared. The distribution of ρrc of MWI, MODIS and GOCI agreed well, except for band 667 nm of MODIS, which might have been saturated in relatively turbid waters. Besides, the Rrs used to retrieve TSM among MWI, MODIS and GOCI was also consistent. The root mean square errors (RMSE), mean biases (MB) and mean ratios (MR) between MWI Rrs and MODIS Rrs (or GOCI Rrs) were less than 0.20 sr?1, 5.52% and within 1 ± 0.023, respectively. In addition, the derived TSM from MWI and GOCI also agreed with a R2 of 0.90, MB of 13.75%, MR of 0.97 and RMSE of 9.43 mg/L. Cross-calibration coefficients retrieved in this paper will contribute to quantitative applications of MWI. This method can be extended easily to other similar ocean color satellite missions.
关键词： atmospheric correction,cross calibration,total suspended matter,open oceans,inland water
更新于2025-09-23 15:22:29
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Marine coastal zones monitoring by shipborne semiautomatic passive optical complex
摘要： For studying of the environmental status of marine coastal areas, it is often necessary to obtain operatively detailed data about water constituents and their distribution over the area. The three-channel passive optical complex for Ecological Monitoring of Marine Areas (EMMA), developed by us, was applied in the Feodosia Bay, the Black Sea, to obtain remotely the absorption indices for the suspended matter, coloured dissolved organic matter, and phytoplankton pigments. It operated from board a vessel for more than 4 h and gave data for approximately 15,000 sea radiance coe?cient spectra. The obtained spectra were processed by the original method giving possibility to suppress negative in?uence of the weather and experiment conditions and to get the absorption index spectra of the water constituents. The data of shipborne remote sensing using EMMA were compared to the estimates retrieved from the measurements on water samples taken at special stations on the route; their correlation turned out to be quite reasonable. The distributions of the suspended matter and coloured organic matter, obtained remotely over the studied area, were discussed. This research showed the possibility of EMMA application for ground truth measurements and for exploring the sea areas close to the coastal line, which cannot be seen from satellites because of cloudiness.
关键词： phytoplankton pigments,coloured dissolved organic matter,marine coastal zones,suspended matter,absorption indices,monitoring,Black Sea,semiautomatic passive optical complex,EMMA,shipborne
更新于2025-09-11 14:12:44
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The Advantages of Landsat 8-OLI-Derived Suspended Particulate Matter Maps for Monitoring the Subtidal Extension of Amazonian Coastal Mud Banks (French Guiana)
摘要： The coast of French Guiana is characterised by the northwestward migration of large mud banks alongshore and by high concentrations of suspended particulate matter (SPM) resulting from the strong influence of the Amazon River outflow. Surface OLI SPM concentration, linked to the footprint of the subtidal part of mud banks due to resuspension and migration processes, was used to develop a method to estimate the location of this footprint. A comparison of the results from this method with those obtained by locating the limit of the wave damping, which characterises muddy coasts, revealed good performance of the method based on recurring SPM values. The migration rates of the mud banks in French Guiana were calculated according to the delimitation of their subtidal parts, and showed slightly higher values (2.31 km/year) than suggested by earlier studies. In comparison with other methods, the migration rate estimated using the method proposed within the framework of this study takes into account the variability of the shape of the subtidal part for the first time. It was also shown that the mud banks existing on the coastal area of French Guiana present two different shapes. Our results clearly demonstrate the advantage of ocean colour data to describe mud banks according to their subtidal part, delimited using the assessment of SPM temporal variability.
关键词： French Guiana,suspended matter,ocean colour,Landsat 8,mud banks
更新于2025-09-04 15:30:14