Lake ice thickness changes with regional hydrometeorology and is closely associated with global climate change.We tested the detection of ice thickness using ground penetrating radar（GPR）in the Hongqipao reservoir.I...Lake ice thickness changes with regional hydrometeorology and is closely associated with global climate change.We tested the detection of ice thickness using ground penetrating radar（GPR）in the Hongqipao reservoir.Ice crystals,gas bubbles,ice density and ice thickness were also determined by concurrently drilling for validation.During the tests the gas bubble content was high in the upper and low in the bottom,ice density varied with the bubble content,and the ice thickness was not homogeneous.By comparisons between radar detected and in-situ measured ice thicknesses with theoretical analyses of the influence of gas bubble content on the dielectric constant,a three-layer model with snow, granular ice,and columnar ice was established and the transmission speed of radar wave within the ice was determined.Experience reveals that the equivalent dielectric constant can be used to evaluate the wave speed and the values at 1/3 ice cover depth can be used as equivalent values.Besides,the difference between the theoretical transmission time and the real detection time induced by large gas bubbles increases nonlinearly with the theoretical transmission time or ice thickness.展开更多
Luquire et al. ' s impedance change model of a rectangular cross section probe coil above a structure with an arbitrary number of parallel layers was used to study the principle of measuring thicknesses of multi-l...Luquire et al. ' s impedance change model of a rectangular cross section probe coil above a structure with an arbitrary number of parallel layers was used to study the principle of measuring thicknesses of multi-layered structures in terms of eddy current testing voltage measurements. An experimental system for multi-layered thickness measurement was developed and several fitting models to formulate the relationships between detected impedance/voltage measurements and thickness are put forward using least square method. The determination of multi-layered thicknesses was investigated after inversing the voltage outputs of the detecting system. The best fitting and inversion models are presented.展开更多
In this study, a special method is proposed for detecting aerosols over land by analyzing satellitemeasured far IR radiation at three channels, 8.7, 11.5, and 12.5 lain. Sensitivity tests revealed that the behavioral ...In this study, a special method is proposed for detecting aerosols over land by analyzing satellitemeasured far IR radiation at three channels, 8.7, 11.5, and 12.5 lain. Sensitivity tests revealed that the behavioral features of radiative brightness temperatures （BTs） at these three channels with increasing optical depth are different among different types of aerosols. Analyzing how BTs and their differences, xBT （BT11.5-BT12.5） and YBT （BT8.7-BT11.5）, behave with varying optical depth can help to qualitatively distinguish among aerosols and semi-quantitatively estimate their optical thicknesses. In addition, the authors found that the vertical density profile of aerosols has little impact on this method.展开更多
基金supported by the National Natural Science Foundation of China(Grant No50879008,40930848)the Open Fund of State Key Laboratory of Frozen Soil Engineering(Grant No SKLFSE200904)
文摘Lake ice thickness changes with regional hydrometeorology and is closely associated with global climate change.We tested the detection of ice thickness using ground penetrating radar（GPR）in the Hongqipao reservoir.Ice crystals,gas bubbles,ice density and ice thickness were also determined by concurrently drilling for validation.During the tests the gas bubble content was high in the upper and low in the bottom,ice density varied with the bubble content,and the ice thickness was not homogeneous.By comparisons between radar detected and in-situ measured ice thicknesses with theoretical analyses of the influence of gas bubble content on the dielectric constant,a three-layer model with snow, granular ice,and columnar ice was established and the transmission speed of radar wave within the ice was determined.Experience reveals that the equivalent dielectric constant can be used to evaluate the wave speed and the values at 1/3 ice cover depth can be used as equivalent values.Besides,the difference between the theoretical transmission time and the real detection time induced by large gas bubbles increases nonlinearly with the theoretical transmission time or ice thickness.
文摘Luquire et al. ' s impedance change model of a rectangular cross section probe coil above a structure with an arbitrary number of parallel layers was used to study the principle of measuring thicknesses of multi-layered structures in terms of eddy current testing voltage measurements. An experimental system for multi-layered thickness measurement was developed and several fitting models to formulate the relationships between detected impedance/voltage measurements and thickness are put forward using least square method. The determination of multi-layered thicknesses was investigated after inversing the voltage outputs of the detecting system. The best fitting and inversion models are presented.
基金supported by the National Basic Research Program of China (Grant No. 2006CB403705)
文摘In this study, a special method is proposed for detecting aerosols over land by analyzing satellitemeasured far IR radiation at three channels, 8.7, 11.5, and 12.5 lain. Sensitivity tests revealed that the behavioral features of radiative brightness temperatures （BTs） at these three channels with increasing optical depth are different among different types of aerosols. Analyzing how BTs and their differences, xBT （BT11.5-BT12.5） and YBT （BT8.7-BT11.5）, behave with varying optical depth can help to qualitatively distinguish among aerosols and semi-quantitatively estimate their optical thicknesses. In addition, the authors found that the vertical density profile of aerosols has little impact on this method.
