采用Raman-Mie激光雷达探测了西安地区夏季气溶肢的光学特性,分析了消光系数、后向散射系数和雷达比在不同天气条件下的变化规律.实验结果表明,强降雨后,气溶肢消光系数在2-5 k m 范围内递减,并在5 k m 以上趋于稳定;相对于降雨前,降雨...采用Raman-Mie激光雷达探测了西安地区夏季气溶肢的光学特性,分析了消光系数、后向散射系数和雷达比在不同天气条件下的变化规律.实验结果表明,强降雨后,气溶肢消光系数在2-5 k m 范围内递减,并在5 k m 以上趋于稳定;相对于降雨前,降雨后低层气溶肢消光系数明显增大,而3 k m 以上高度范围内雷达比减小.这可能是由雨后气溶肢沉降、底层水汽密度增加所引起的.统计结果表明,晴天无云时,2-3 k m 范围内气溶肢的消光系数和雷达比均比较稳定,消光系数在0. 2-0. 3 km^-1之间,雷达比的平均值约为50 sr;3 -5 k m 范围内消光系数和雷达比均随高度递减;5-8 k m 范围内,消光系数和雷达比逐渐趋于稳定,消光系数和雷达比的平均值分别约为0.05 km^-1和20sr,表明此范围内仍有微量的气溶肢粒子存在.实验期间,水云的雷达比约为17 sr.展开更多
The linear optical properties and the surface-enhanced Raman scattering (SERS) effect of spherical palladium nanoparticle dimers are analyzed theoretically using generalized Mie theory. The calculation results demonst...The linear optical properties and the surface-enhanced Raman scattering (SERS) effect of spherical palladium nanoparticle dimers are analyzed theoretically using generalized Mie theory. The calculation results demonstrate that the near-field coupling effect greatly influences the absorption, scattering and extinction spectra of nanoparticle dimers. The surface plasmon resonance wave- length red-shifts dramatically as the separation between nanoparticles decreases. Because of the near-field coupling between nanoparticles and the size effect, the maximum SERS enhancement factor at the 'hot spot' between palladium nanoparticle dimers is as high as 107-108, while the averaged SERS enhancement factor over the entire nanoparticle surface is in the range of 105-106. The deviation between the position of the peak in the extinction spectrum and the wavelength for maximum surface-averaged enhancement for the Pd nanoparticle dimers indicates that localized surface plasmon resonance has different influences on the far and near fields. These theoretical results may help to reveal the relationship between the far and near fields, as well as understand the mechanism of electromagnetic enhancement in the surface-enhanced scattering of transition metals.展开更多
Lidar methods for observing mineral dust aerosols are reviewed.These methods include Mie scattering lidars,polarization lidars,Raman scattering lidars,high-spectral-resolution lidars,and fluorescence lidars.Some of th...Lidar methods for observing mineral dust aerosols are reviewed.These methods include Mie scattering lidars,polarization lidars,Raman scattering lidars,high-spectral-resolution lidars,and fluorescence lidars.Some of the lidar systems developed by the authors and the results of the observations and applications are introduced.The largest advantage of the lidar methods is that they can observe vertical distribution of aerosols continuously with high temporal and spatial resolutions.Networks of ground-based lidars provide useful data for understanding the distribution and movement of mineral dust and other aerosols.The lidar network data are actually used for validation and assimilation of dust transport models,which can evaluate emission,transport,and deposition of mineral dust.The lidar methods are also useful for measuring the optical characteristics of aerosols that are essential to assess the radiative effects of aerosols.Evolution of the lidar data analysis methods for aerosol characterization is also reviewed.Observations from space and ground-based networks are two important approaches with the lidar methods in the studies of the effects of mineral dust and other aerosols on climate and the environment.Directions of the researches with lidar methods in the near future are discussed.展开更多
文摘采用Raman-Mie激光雷达探测了西安地区夏季气溶肢的光学特性,分析了消光系数、后向散射系数和雷达比在不同天气条件下的变化规律.实验结果表明,强降雨后,气溶肢消光系数在2-5 k m 范围内递减,并在5 k m 以上趋于稳定;相对于降雨前,降雨后低层气溶肢消光系数明显增大,而3 k m 以上高度范围内雷达比减小.这可能是由雨后气溶肢沉降、底层水汽密度增加所引起的.统计结果表明,晴天无云时,2-3 k m 范围内气溶肢的消光系数和雷达比均比较稳定,消光系数在0. 2-0. 3 km^-1之间,雷达比的平均值约为50 sr;3 -5 k m 范围内消光系数和雷达比均随高度递减;5-8 k m 范围内,消光系数和雷达比逐渐趋于稳定,消光系数和雷达比的平均值分别约为0.05 km^-1和20sr,表明此范围内仍有微量的气溶肢粒子存在.实验期间,水云的雷达比约为17 sr.
基金supported by the National Natural Science Foundation of China (20703032)National Basic Research Program of China (2009CB930703)Natural Science Foundation of Fujian Province of China (E0710028)
文摘The linear optical properties and the surface-enhanced Raman scattering (SERS) effect of spherical palladium nanoparticle dimers are analyzed theoretically using generalized Mie theory. The calculation results demonstrate that the near-field coupling effect greatly influences the absorption, scattering and extinction spectra of nanoparticle dimers. The surface plasmon resonance wave- length red-shifts dramatically as the separation between nanoparticles decreases. Because of the near-field coupling between nanoparticles and the size effect, the maximum SERS enhancement factor at the 'hot spot' between palladium nanoparticle dimers is as high as 107-108, while the averaged SERS enhancement factor over the entire nanoparticle surface is in the range of 105-106. The deviation between the position of the peak in the extinction spectrum and the wavelength for maximum surface-averaged enhancement for the Pd nanoparticle dimers indicates that localized surface plasmon resonance has different influences on the far and near fields. These theoretical results may help to reveal the relationship between the far and near fields, as well as understand the mechanism of electromagnetic enhancement in the surface-enhanced scattering of transition metals.
基金Supported by the National Natural Science Foundation of China(41205014 and 41375031)Fundamental Research Funds for the Central Universities(lzujbky-2013-106)
文摘Lidar methods for observing mineral dust aerosols are reviewed.These methods include Mie scattering lidars,polarization lidars,Raman scattering lidars,high-spectral-resolution lidars,and fluorescence lidars.Some of the lidar systems developed by the authors and the results of the observations and applications are introduced.The largest advantage of the lidar methods is that they can observe vertical distribution of aerosols continuously with high temporal and spatial resolutions.Networks of ground-based lidars provide useful data for understanding the distribution and movement of mineral dust and other aerosols.The lidar network data are actually used for validation and assimilation of dust transport models,which can evaluate emission,transport,and deposition of mineral dust.The lidar methods are also useful for measuring the optical characteristics of aerosols that are essential to assess the radiative effects of aerosols.Evolution of the lidar data analysis methods for aerosol characterization is also reviewed.Observations from space and ground-based networks are two important approaches with the lidar methods in the studies of the effects of mineral dust and other aerosols on climate and the environment.Directions of the researches with lidar methods in the near future are discussed.
