A correction considering the effects of atmospheric temperature, pressure, and Mie contamination must be performed for wind retrieval from a Rayleigh Doppler lidar（RDL）, since the so-called Rayleigh response is dire...A correction considering the effects of atmospheric temperature, pressure, and Mie contamination must be performed for wind retrieval from a Rayleigh Doppler lidar（RDL）, since the so-called Rayleigh response is directly related to the convolution of the optical transmission of the frequency discriminator and the Rayleigh–Brillouin spectrum of the molecular backscattering. Thus, real-time and on-site profiles of atmospheric pressure, temperature, and aerosols should be provided as inputs to the wind retrieval. Firstly, temperature profiles under 35 km and above the altitude are retrieved, respectively,from a high spectral resolution lidar（HSRL） and a Rayleigh integration lidar（RIL） incorporating to the RDL. Secondly,the pressure profile is taken from the European Center for Medium range Weather Forecast（ECMWF） analysis, while radiosonde data are not available. Thirdly, the Klett–Fernald algorithms are adopted to estimate the Mie and Rayleigh components in the atmospheric backscattering. After that, the backscattering ratio is finally determined in a nonlinear fitting of the transmission of the atmospheric backscattering through the Fabry–Perot interferometer（FPI） to a proposed model.In the validation experiments, wind profiles from the lidar show good agreement with the radiosonde in the overlapping altitude. Finally, a continuous wind observation shows the stability of the correction scheme.展开更多
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
Observation of optical properties of atmospheric aerosols, especially their behavior near the surface level, is indispensable for better understanding of atmospheric environmental conditions. Concurrent observations o...Observation of optical properties of atmospheric aerosols, especially their behavior near the surface level, is indispensable for better understanding of atmospheric environmental conditions. Concurrent observations of ground-based instruments and satellite-borne sensors are useful for attaining improved accuracy in the observation of relatively wide area. In the present paper, aerosol parameters in the lower troposphere are monitored using a plan position indicator (PPI) lidar, ground-sampling instruments (a nephelometer, an aethalometer, and optical particle counters), as well as a sunphotometer. The purpose of these observations is to retrieve the aerosol extinction coefficient (AEC) and aerosol optical thickness (AOT) simultaneously at the overpass time of Landsat-8 satellite. The PPI lidar, operated at 349 nm, provides nearly horizontal distribution of AEC in the lower part of the atmospheric boundary layer. For solving the lidar equation, the boundary condition and lidar ratio are determined from the data of ground sampling instruments. The value of AOT, on the other hand, is derived from sunphotometer, and used to analyze the visible band imagery of Landsat-8 satellite. The radiative transfer calculation is conducted using the MODTRAN code with the original aerosol type that has been determined from the ground sampling data coupled with the Mie scattering calculation. Reasonable agreement is found between the spatial distribution of AEC from the PPI lidar and that of AOT from the blue band (band 2) of Landsat-8. The influence of AOT on the values of apparent surface reflectance is also discussed.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.41174131,41274151,41304123,41121003 and 41025016)
文摘A correction considering the effects of atmospheric temperature, pressure, and Mie contamination must be performed for wind retrieval from a Rayleigh Doppler lidar（RDL）, since the so-called Rayleigh response is directly related to the convolution of the optical transmission of the frequency discriminator and the Rayleigh–Brillouin spectrum of the molecular backscattering. Thus, real-time and on-site profiles of atmospheric pressure, temperature, and aerosols should be provided as inputs to the wind retrieval. Firstly, temperature profiles under 35 km and above the altitude are retrieved, respectively,from a high spectral resolution lidar（HSRL） and a Rayleigh integration lidar（RIL） incorporating to the RDL. Secondly,the pressure profile is taken from the European Center for Medium range Weather Forecast（ECMWF） analysis, while radiosonde data are not available. Thirdly, the Klett–Fernald algorithms are adopted to estimate the Mie and Rayleigh components in the atmospheric backscattering. After that, the backscattering ratio is finally determined in a nonlinear fitting of the transmission of the atmospheric backscattering through the Fabry–Perot interferometer（FPI） to a proposed model.In the validation experiments, wind profiles from the lidar show good agreement with the radiosonde in the overlapping altitude. Finally, a continuous wind observation shows the stability of the correction scheme.
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.
文摘Observation of optical properties of atmospheric aerosols, especially their behavior near the surface level, is indispensable for better understanding of atmospheric environmental conditions. Concurrent observations of ground-based instruments and satellite-borne sensors are useful for attaining improved accuracy in the observation of relatively wide area. In the present paper, aerosol parameters in the lower troposphere are monitored using a plan position indicator (PPI) lidar, ground-sampling instruments (a nephelometer, an aethalometer, and optical particle counters), as well as a sunphotometer. The purpose of these observations is to retrieve the aerosol extinction coefficient (AEC) and aerosol optical thickness (AOT) simultaneously at the overpass time of Landsat-8 satellite. The PPI lidar, operated at 349 nm, provides nearly horizontal distribution of AEC in the lower part of the atmospheric boundary layer. For solving the lidar equation, the boundary condition and lidar ratio are determined from the data of ground sampling instruments. The value of AOT, on the other hand, is derived from sunphotometer, and used to analyze the visible band imagery of Landsat-8 satellite. The radiative transfer calculation is conducted using the MODTRAN code with the original aerosol type that has been determined from the ground sampling data coupled with the Mie scattering calculation. Reasonable agreement is found between the spatial distribution of AEC from the PPI lidar and that of AOT from the blue band (band 2) of Landsat-8. The influence of AOT on the values of apparent surface reflectance is also discussed.
