Olivine exposures at the central peak of Copernicus crater of the Earth＇s Moon have been confirmed by telescope observations and Clementine spectra data. Using these exposures as training sites, this study used a met...Olivine exposures at the central peak of Copernicus crater of the Earth＇s Moon have been confirmed by telescope observations and Clementine spectra data. Using these exposures as training sites, this study used a method of combining two spectral indices （950 nm/750 nm and 2000 nm/1500 nm）, one maturity index （Is/FeO）, and four chemical content indices （FeO, Mg, Al, Ca）, through a decision tree classifier, to map olivine-rich units on the west lunar surface based on mosaicked Clementine image （500 m pixel size）. Most classified olivine exposures are found inside craters or on their rays, suggesting that olivine exposures are directly associated with the impact processes. The results have been validated in several selected sites, though further validations with data from the newest missions are strongly needed.展开更多
Rain is one of the main sources of error in dual-frequency altimeter Jason-1 wind measurement. In this study, a new radar altimeter backscatter model is proposed and validated to eliminate rain effects. The model take...Rain is one of the main sources of error in dual-frequency altimeter Jason-1 wind measurement. In this study, a new radar altimeter backscatter model is proposed and validated to eliminate rain effects. The model takes into account attenuation, volume backscattering, and sea surface perturbation by raindrops under rain conditions. A match-up dataset is built to evaluate rain effects, in combination with the Jason-1 normalized radar cross section, precipitation radar data from the Tropical Rainfall Measuring Mission, and sea surface wind reanalysis data from the European Centre for Medium-Range Weather Forecasts. The results show that rain-induced surface perturbation backscatter increases with rain rate at Ku-band, but their correlation at C-band is poor. In addition, rain surface perturbation and attenuation have major effects on radar altimeter wind measurements. Finally, a rain correction model for Jason-1 winds is developed and validation results prove its ability to reduce rain-induced inaccuracies in wind retrievals.展开更多
基金supported by the National High Technology Research and Development Program(No.2010AA12220101 and 2009AA12Z310)National Natural Science Foundation of China(No.40871202 and 41002120)
文摘Olivine exposures at the central peak of Copernicus crater of the Earth＇s Moon have been confirmed by telescope observations and Clementine spectra data. Using these exposures as training sites, this study used a method of combining two spectral indices （950 nm/750 nm and 2000 nm/1500 nm）, one maturity index （Is/FeO）, and four chemical content indices （FeO, Mg, Al, Ca）, through a decision tree classifier, to map olivine-rich units on the west lunar surface based on mosaicked Clementine image （500 m pixel size）. Most classified olivine exposures are found inside craters or on their rays, suggesting that olivine exposures are directly associated with the impact processes. The results have been validated in several selected sites, though further validations with data from the newest missions are strongly needed.
基金Supported by the Knowledge Innovation Program of Chinese Academy of Sciences (No.Y0S04300KB)the Major Program for the Research Equipment of Chinese Academy of Sciences (No.YZ200946)
文摘Rain is one of the main sources of error in dual-frequency altimeter Jason-1 wind measurement. In this study, a new radar altimeter backscatter model is proposed and validated to eliminate rain effects. The model takes into account attenuation, volume backscattering, and sea surface perturbation by raindrops under rain conditions. A match-up dataset is built to evaluate rain effects, in combination with the Jason-1 normalized radar cross section, precipitation radar data from the Tropical Rainfall Measuring Mission, and sea surface wind reanalysis data from the European Centre for Medium-Range Weather Forecasts. The results show that rain-induced surface perturbation backscatter increases with rain rate at Ku-band, but their correlation at C-band is poor. In addition, rain surface perturbation and attenuation have major effects on radar altimeter wind measurements. Finally, a rain correction model for Jason-1 winds is developed and validation results prove its ability to reduce rain-induced inaccuracies in wind retrievals.
