排序方式: 共有86条查询结果,搜索用时 0 毫秒
81.
82.
P. Weibring J. Swartling H. Edner S. Svanberg T. Caltabiano D. Condarelli G. Cecchi L. Pantani 《Optics and Lasers in Engineering》2002,37(2-3)
The emissions of sulphur dioxide from the Italian volcanoes Mt. Etna and Stromboli were studied in ship-borne underpasses of their plumes. Four different optical spectroscopy techniques were used and inter-compared. All techniques utilise the absorption signature of the gas in the wavelength region of around 300 nm. A differential absorption lidar was employed in active gas concentration assessment. In parallel, a differential optical absorption spectroscopy system (DOAS) provided spectrally resolved absorption spectra. In one configuration the DOAS used a vertically looking telescope and the absorption of the sky-light was studied, while a different DOAS implementation utilised the sun disc as the light source in slant-angle, long-path absorption measurements. Parallel measurements with the customary correlation spectroscopy method were also performed. Path length Monte Carlo simulations of the down-welling radiation through the volcanic plume at different sun altitude and azimuth angles have been performed taking into account also the effects of other geometric parameters as the plume height and extension. The results are discussed with special emphasis on systematic effects due to scattering. 相似文献
83.
Xiaomei Lu Xuguo Zhang Nicola Spinelli 《Journal of Quantitative Spectroscopy & Radiative Transfer》2011,112(2):320-328
A modified two-wavelength lidar inversion algorithm is proposed to aid in the retrieval of aerosol extinction-to-backscatter ratios (lidar ratio) as well as backscatter coefficients and extinction color ratios from simultaneous two-wavelength elastic backscatter lidar measurements. To demonstrate the feasibility of the algorithm, both the Raman method and the two-wavelength method have been applied to the ground-based measurements at 355 and 532 nm; moreover, it has been applied to the data acquired by the Cloud Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) lidar, and to the simultaneous ground-based lidar measurements carried out at Napoli (southern Italy, 40.838 °N, 14.183 °E, 118 m above sea level). Three cases of Saharan dust transport towards Europe have been considered. From the comparison, it can be found that the values of lidar ratio and backscatter coefficient retrieved by the modified two-wavelength algorithm are in good agreement with those obtained by the Raman method. Moreover the retrieved mean values of the lidar ratios and color ratios are in agreement with those reported by other authors. 相似文献
84.
基于EMD-DISPO的Mie散射激光雷达回波信号去噪方法研究 总被引:2,自引:0,他引:2
激光雷达回波信号是典型的非稳态、非平稳信号,用传统的滤波方法难以对其进行有效地处理.利用经验模式分解方法(EMD)将信号按照不同的特征时间尺度分解为不同的IMF分量,将含有噪声的高频IMF分量剔除,可达到去噪的目的.但如果简单地将高频分量直接剔除,有可能造成有效信号的损失.可提出将EMD方法与Savitzky-Gola... 相似文献
85.
This letter describes a flash Lidar imaging technique that uses a streak tube camera as a receiver to detect short scale surface wave fields for oceanographic, underwater target and coastal measurements. The range and intensity imaging of short scale sea-waves and underwater targets can be supplied by this system through light reflected from the surface of the sea and targets. Through a surface scattering model, more accurate range and intensity information can be extracted. The technique can be applied to surface wave measurements and underwater target detection with high resolution. The feasibility of this technique is demonstrated by applying the technique to data acquired by shipborne Streak Tube Imaging Lidar (STIL) in the Yellow Sea and also the East and South China Seas. 相似文献
86.
《Optics and Lasers in Engineering》2002,37(2-3)
We represent the results of our investigations on size distribution of atmospheric aerosol particles by means of a multiwavelength lidar based on Nd : YAG and Ti : Sa lasers equipped with frequency multipliers. The measurements were performed in mountainous areas. 相似文献