Active microwave and passive optical remote sensing data have demonstrated their respective advantages in inversion of surface soil moisture content. A new semi-empirical model is presented for soil moisture content r...Active microwave and passive optical remote sensing data have demonstrated their respective advantages in inversion of surface soil moisture content. A new semi-empirical model is presented for soil moisture content retrieval in vegetation-covered areas, using ENVISAT-ASAR and LANDSAT-TM data collaboratively. Derivation of the algorithm is based on simplification of the Michigan Microwave Canopy Scattering Model （MIMICS）. In the model, the ground surface is divided into a canopy layer and a soil layer, and empirical relationships simulated among vegetation water mass We, the backscatter coefficient σpq1, the bidirectional scattering coefficient σpq2 and the extinction coefficient τp. The key input parameters of the semi-empirical model are reduced to only the leaf area index （LAI）, which can be easily inverted by the optical model PROSAIL, allowing coupling of the microwave and optical models to be achieved. Also, vegetation RMS height （Svcg） is introduced to correct for the radar-shadow effect caused by over-laying vegetation. Analysis of the parameter sensitivity of the semi-empirical model showed that when the regional Leaf Area Index is small （LAI≤3）, the model is more applicable. Soil moisture distribution in the study area was mapped using the semi-empirical model and field ground measurements used for model validation. This showed that, after correction of the radar-shadow effect, the average relative error （Er） between ground-measured and semi-empirical model-derived estimates of soil moisture decreased from 17.6% to 10.4%, while the RMS reduced from 0.055 to 0.031 g cm^-3. The accuracy of soil moisture estimates from the semi-empirical model is much better than for the MIMICS model （Er = 22.7%, RMS = 0.068 g cm^-3）, showing that the semi-empirical model is efficient at obtaining regional surface soil moisture contents when LAI is small.展开更多
For enhancing the 2.0 μm band fluorescence of Ho^(3+), a certain amount of WO_3 oxide was introduced into Ho^(3+)/Tm^(3+)/Yb^(3+) tri-doped tellurite glass prepared using melt-quenching technique. The prepared tri-do...For enhancing the 2.0 μm band fluorescence of Ho^(3+), a certain amount of WO_3 oxide was introduced into Ho^(3+)/Tm^(3+)/Yb^(3+) tri-doped tellurite glass prepared using melt-quenching technique. The prepared tri-doped tellurite glass was characterized by the absorption spectra, fluorescence emission and Raman scattering spectra, together with the stimulated absorption, emission cross-sections and gain coefficient. The research results show that the introduction of WO_3 oxide can further improve the 2.0 μm band fluorescence emission through the enhanced phonon-assisted energy transfers between Ho^(3+)/Tm^(3+)/Yb^(3+) ions under the excitation of 980 nm laser diode(LD). Meanwhile, the maximum gain coefficient of Ho^(3+) at 2.0 μm band reaches about 2.36 cm^(-1). An intense 2.0 μm fluorescence emission can be realized.展开更多
基金supported by National Basic Research Program of China (Grant No. 2007CB714407)Basic Research Program of the Chinese Academy of Surveying and Mapping (Grant Nos. 7771023 and 7771017)
文摘Active microwave and passive optical remote sensing data have demonstrated their respective advantages in inversion of surface soil moisture content. A new semi-empirical model is presented for soil moisture content retrieval in vegetation-covered areas, using ENVISAT-ASAR and LANDSAT-TM data collaboratively. Derivation of the algorithm is based on simplification of the Michigan Microwave Canopy Scattering Model （MIMICS）. In the model, the ground surface is divided into a canopy layer and a soil layer, and empirical relationships simulated among vegetation water mass We, the backscatter coefficient σpq1, the bidirectional scattering coefficient σpq2 and the extinction coefficient τp. The key input parameters of the semi-empirical model are reduced to only the leaf area index （LAI）, which can be easily inverted by the optical model PROSAIL, allowing coupling of the microwave and optical models to be achieved. Also, vegetation RMS height （Svcg） is introduced to correct for the radar-shadow effect caused by over-laying vegetation. Analysis of the parameter sensitivity of the semi-empirical model showed that when the regional Leaf Area Index is small （LAI≤3）, the model is more applicable. Soil moisture distribution in the study area was mapped using the semi-empirical model and field ground measurements used for model validation. This showed that, after correction of the radar-shadow effect, the average relative error （Er） between ground-measured and semi-empirical model-derived estimates of soil moisture decreased from 17.6% to 10.4%, while the RMS reduced from 0.055 to 0.031 g cm^-3. The accuracy of soil moisture estimates from the semi-empirical model is much better than for the MIMICS model （Er = 22.7%, RMS = 0.068 g cm^-3）, showing that the semi-empirical model is efficient at obtaining regional surface soil moisture contents when LAI is small.
基金supported by the National Natural Science Foundation of China(No.61178063)the Graduate Innovative Scientific Research Project of Zhejiang Province(No.YK2010048)+2 种基金the Natural Science Foundation of Ningbo City(No.2016A610061)the K.C.Wong Magna FundHu Lan Outstanding Doctoral Fund in Ningbo University
文摘For enhancing the 2.0 μm band fluorescence of Ho^(3+), a certain amount of WO_3 oxide was introduced into Ho^(3+)/Tm^(3+)/Yb^(3+) tri-doped tellurite glass prepared using melt-quenching technique. The prepared tri-doped tellurite glass was characterized by the absorption spectra, fluorescence emission and Raman scattering spectra, together with the stimulated absorption, emission cross-sections and gain coefficient. The research results show that the introduction of WO_3 oxide can further improve the 2.0 μm band fluorescence emission through the enhanced phonon-assisted energy transfers between Ho^(3+)/Tm^(3+)/Yb^(3+) ions under the excitation of 980 nm laser diode(LD). Meanwhile, the maximum gain coefficient of Ho^(3+) at 2.0 μm band reaches about 2.36 cm^(-1). An intense 2.0 μm fluorescence emission can be realized.
