Over the past few decades,an increasing number of marine activities have been conducted in the East China Sea,including the construction of various marine structures and the passage of large ships.Marine safety issues...Over the past few decades,an increasing number of marine activities have been conducted in the East China Sea,including the construction of various marine structures and the passage of large ships.Marine safety issues are paramount and are becoming more important with respect to the likely increase in size of ocean waves in relation to global climate change and associated typhoons.In addition,swells also can be very dangerous because they induce the resonance of floating structures,including ships.This study focuses on an investigation of swells in the East China Sea and uses hindcast data for waves over the past 5 years in a numerical model,WAVEWATCH III(WW3),together with historical climate data.The numerical calculation domain covers the entire North West Pacific.Next,swells are separated and analyzed using simulated wave fields,and both the characteristics and generation mechanisms of swells are investigated.展开更多
Snow-cover parameters are important indicator factors for hydrological models and climate change studies and have typical vertical stratification characteristics. Remote sensing can be used for large-scale monitoring ...Snow-cover parameters are important indicator factors for hydrological models and climate change studies and have typical vertical stratification characteristics. Remote sensing can be used for large-scale monitoring of snow parameters. In SAR(Interferometric Synthetic Aperture Radar) technology has advantages in detecting the vertical structure of snow cover. As a basis of snow vertical structure detection using In SAR, a scattering model can reveal the physical process of interaction between electromagnetic waves and snow. In recent years, the In SAR scattering model for single-layer snow has been fully studied;however, it cannot be applied to the case of multi-layer snow. To solve this problem, a multi-layer snow scattering mode is proposed in this paper, which applies the QCA(Quad-Crystal Approximation) theory to describe the coherent scattering characteristics of snow and introduces a stratification factor to describe the influence of snow stratification on the crosscorrelation of SAR echoes. Based on the proposed model, we simulate an In SAR volumetric correlation of different types of multi-layer snow at the X band(9.6 GHz). The results show that this model is suitable for multi-layer snow, and the sequence of sub-layers of snow has a significant influence on the volumetric correlation. Compared to the single layer model, the multi-layer model can predict a polarization difference in the volumetric correlation more accurately and thus has a wider scope of application. To make the model more available for snow parameter inversion, a simplified multi-layer model was also developed.The model did not have polarization information compared to that of the full model but showed good consistency with the full model. The phase of the co-polarization In SAR volumetric correlation difference is more sensitive to snow parameters than that of the phase difference of the co-polarization In SAR volumetric correlation and more conducive to the development of a parameter-inversion algorithm. The model can be applied to deepen our understanding of In SAR scattering mechanisms and to develop a snow parameter inversion algorithm.展开更多
基金funded by the National Natural Science Fundation of China(Nos.51579091,51379071,and 51137002)the National Science Fund for Distinguished Young Scholars(No.51425901)+3 种基金the Qing Lan Project of Jiangsu Provincethe Basic Research Fund from State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering,Hohai University(Nos.20145027512 and 20145028412)the Short-term Research Visits project supported by Disaster Prevention Research Institute of Kyoto University(No.27S-02)the Fundamental Research Funds for the Central Universities of Hohai University(No.2016B05214)
文摘Over the past few decades,an increasing number of marine activities have been conducted in the East China Sea,including the construction of various marine structures and the passage of large ships.Marine safety issues are paramount and are becoming more important with respect to the likely increase in size of ocean waves in relation to global climate change and associated typhoons.In addition,swells also can be very dangerous because they induce the resonance of floating structures,including ships.This study focuses on an investigation of swells in the East China Sea and uses hindcast data for waves over the past 5 years in a numerical model,WAVEWATCH III(WW3),together with historical climate data.The numerical calculation domain covers the entire North West Pacific.Next,swells are separated and analyzed using simulated wave fields,and both the characteristics and generation mechanisms of swells are investigated.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41471065 & 41471066)the International Partnership Program of Chinese Academy of Sciences (Grant No. 131C11KYSB20160061)+1 种基金the Science & Technology Basic Resources Investigation Program of China (Grant No. 2017FY100502)the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDA19070201)
文摘Snow-cover parameters are important indicator factors for hydrological models and climate change studies and have typical vertical stratification characteristics. Remote sensing can be used for large-scale monitoring of snow parameters. In SAR(Interferometric Synthetic Aperture Radar) technology has advantages in detecting the vertical structure of snow cover. As a basis of snow vertical structure detection using In SAR, a scattering model can reveal the physical process of interaction between electromagnetic waves and snow. In recent years, the In SAR scattering model for single-layer snow has been fully studied;however, it cannot be applied to the case of multi-layer snow. To solve this problem, a multi-layer snow scattering mode is proposed in this paper, which applies the QCA(Quad-Crystal Approximation) theory to describe the coherent scattering characteristics of snow and introduces a stratification factor to describe the influence of snow stratification on the crosscorrelation of SAR echoes. Based on the proposed model, we simulate an In SAR volumetric correlation of different types of multi-layer snow at the X band(9.6 GHz). The results show that this model is suitable for multi-layer snow, and the sequence of sub-layers of snow has a significant influence on the volumetric correlation. Compared to the single layer model, the multi-layer model can predict a polarization difference in the volumetric correlation more accurately and thus has a wider scope of application. To make the model more available for snow parameter inversion, a simplified multi-layer model was also developed.The model did not have polarization information compared to that of the full model but showed good consistency with the full model. The phase of the co-polarization In SAR volumetric correlation difference is more sensitive to snow parameters than that of the phase difference of the co-polarization In SAR volumetric correlation and more conducive to the development of a parameter-inversion algorithm. The model can be applied to deepen our understanding of In SAR scattering mechanisms and to develop a snow parameter inversion algorithm.
