共查询到17条相似文献,搜索用时 31 毫秒
1.
2.
基于蒙特卡洛模拟方法,建立了一个水中激光偏振辐射传输模型,用于模拟分析船载偏振激光雷达水体垂直剖面的偏振探测回波,分析了不同光学参数的水体和激光雷达测量模式下的偏振测量误差。使用高斯分布设置了三种深度分布在10~30 m的低、中、高浓度散射层,其叶绿素a峰值浓度分别为0.1 mg/m3、1 mg/m3和10 mg/m3。模拟了激光发射波长为532 nm,接收视场角为10~1000 mrad的船载海洋激光雷达的偏振回波信号,并分析了影响偏振测量误差的主要因素。研究结果表明,由于激光在水中的多次散射过程,随着探测深度、叶绿素a浓度和接收视场角的增大,激光雷达接收光信号的单次散射率不断降低,导致激光雷达直接测量的退偏振比的误差随之增大。以100 mrad接收视场角为例,中浓度散射层情况下,在散射层上(0~10 m)、散射层中(10~30 m)和散射层下(30~40 m)的退偏振比相对误差分别为16%、125%、281%;在散射层中,低、中、高三种浓度散射层的退偏振比相对误差分别为54%、125%、731%。视场角从10 mrad增大到1000 mrad时,退偏振比相对误差逐渐增大,在中浓度散射层情况下,其在散射层上、散射层中和散射层下的变化范围分别为6%~28%、17%~452%和10%~734%。文中结果表明,偏振海洋激光雷达探测水体退偏振比时,由于多次散射过程的影响,传统的退偏振比算法会引入较大误差,有必要在反演算法中对其进行校正,以提高激光雷达的探测精度。 相似文献
3.
《中国激光》2015,(12)
利用蒙特卡罗方法模拟了多层离散随机介质对激光的偏振多次散射,结合激光雷达的特点,给出了半解析蒙特卡罗模拟方法的具体模拟步骤,考虑了光子在随机游走时,跨越分界层时引起的自由程调整,根据Mie散射相函数对不同介质层进行了散射方向抽样,利用该方法计算了双层和三层水云的雷达多次散射去极化率随穿透深度的变化。从计算结果可以看出,随着穿透深度的增加,雷达去极化率增强,激光在从一种介质入射到另一种介质时,其去极化率增加的速度不同,分析了粒子有效半径、单次散射相函数以及消光系数对雷达去极化率的影响。该方法可以应用于偏振激光雷达对非各向同性云层或气溶胶微物理和光学特性的遥感反演。 相似文献
4.
5.
6.
7.
研究了考虑多次散射的卷云几何特征和光学特性反演方法,对反演卷云高度和卷云激光雷达比的方法进行了改进。采用多次散射因子对卷云消光系数曲线进行修正,选取云底及云顶附近高度消光系数变化率的均值求解云层高度修正误差,对微分零交叉法求解得到的卷云高度进行修正,实现了较为精确的激光雷达云层高度反演。采用以边界值处消光系数和卷云光学厚度为约束条件的粒子群算法,求解卷云有效激光雷达比,选用半解析Monte Carlo方法,计算总散射信号与一次散射信号的比值,并结合Platt多次散射因子方程求得多次散射因子,实现了卷云激光雷达比的准确求解。使用Mie散射激光雷达真实回波信号进行了验证。结果表明,该改进方法具有较高的精度,更具应用价值。 相似文献
8.
9.
介绍了一台新型偏振-米散射激光雷达用于探测大气气溶胶和卷云的消光特性及偏振特性。为了验证激光雷达探测性能可靠性,采用了3种方法:一是对偏振-米散射激光雷达主要性能参量指标的测定;二是偏振-米散射激光雷达与同类激光雷达对比实验;三是偏振-米散射激光雷达与太阳辐射计探测光学厚度对比实验。实验验证了该系统性能稳定,对比实验探测结果基本一致,探测数据可靠。2007-02~2007-05,利用偏振-米散射激光雷达取得了合肥地区卷云退偏振比的观测结果。结果表明,卷云的退偏振比随高度增加而呈现上升趋势,在7km~12km高度范围内,退偏比在0.2~0.5之间,其平均值为0.36±0.06。 相似文献
10.
11.
Volger P. Zhaoyan Liu Sugimoto N. 《Geoscience and Remote Sensing, IEEE Transactions on》2002,40(3):550-559
Spaceborne lidar observations have a great potential to improve our knowledge of the atmosphere. However, contrary to ground-based or airborne lidar measurements in observations from space multiple scattering (MS) has to be accounted for under all atmospheric conditions. A simple way to achieve this is to introduce the approximative MS factor F in the single scattering lidar equation. We determined F for measurements of aerosols, ice and water clouds as they were planned with the Japanese space lidar ELISE. We found that F is almost constant in cirrus clouds and in water clouds which are penetrable by lidar. In aerosol layers F depends on penetration depth, extinction coefficient and aerosol type. In comparison to LITE the MS factor is smaller (for aerosols and water clouds) or almost equal (cirrus) 相似文献
12.
Duda D.P. Spinhirne J.D. Eloranta E.W. 《Geoscience and Remote Sensing, IEEE Transactions on》2001,39(1):92-101
Estimates of the effect of pulse stretching on satellite laser altimetry, such as planned for the Geoscience Laser Altimeter System (GLAS), by cloud multiple scattering were made from an analytical method and with Monte Carlo simulations. Altimetry is dependent on the time required for a laser pulse to complete the roundtrip to the surface and return to the transmitter. Since a transmitted Gaussian pulse will be stretched by the effects of multiple scattering, the use of the pulse centroid as the receive time will produce a biased measurement or an apparent delay in the receive time. The magnitude of this delay was found to be dependent on several factors including cloud height, cloud optical depth, cloud particle size, particle shape, and receiver field of view. The delay was found to be largest for low-level clouds with particle radii of 3-20 μm, potentially amounting to altimetry biases of tens of cm. Alternate methods for measuring the receive time, such as a simple Gaussian fit of the return pulse peak reduce the path delay estimates for all cloud conditions. Since GLAS is a dual mode instrument that includes an atmospheric lidar channel, altimeter measurements that are likely to be significantly contaminated by multiple scattering can be identified 相似文献
13.
14.
考虑多次散射影响的斜程能见度反演方法研究 总被引:3,自引:2,他引:1
提出了一种在低能见度天气条件下考虑多次散射影响时激光雷达反演斜程能见度的组合算法。首先,根据Koschmieder定律构建能见度方程,确定斜程能见度与大气光学厚度的依赖关系;其次,根据多次散射激光雷达方程采用双仰角法反演大气光学厚度,并采用半解析Monte Carlo法计算多次散射对单次散射比值;最后,求出考虑多次散射影响时的斜程能见度。使用地基激光雷达垂直探测进行斜程分解的回波信号数据,进行了实验验证。结果表明,在能见度小于1km时,考虑与未考虑多次散射影响的斜程能见度相对误差达9%,并且随着能见度的降低,多次散射对单次散射比值逐渐增大,多次散射作用增强。因此,研究低能见度天气条件下,多次散射的影响是非常必要的。 相似文献
15.
一台532 nm单波长的偏振米散射激光雷达用于测量大气后向散射回波信号和线性退偏振比?。为了准确获得大气气溶胶和云的退偏振特性,两个偏振通道的标定因子k必须精确确定。采用三种不同的实验方法来确定偏振激光雷达的标定因子,详细叙述了测定方法、过程、结果及误差分析。最后,将标定后的激光雷达探测结果与CALIPSO数据进行比较,进一步验证了方法的可行性。 相似文献
16.
《Geoscience and Remote Sensing, IEEE Transactions on》1993,31(1):56-63
An analytical evaluation which demonstrates that a calibrated 10.6-μm-wavelength lidar can measure the mean radius and the effective radius of the drop size distribution in a water cloud is discussed. The radius parameter observed is a weighted average over the penetration depth of the pulse, with weighting factor decreasing with optical depth. In this method the lidar signal is integrated and boundary conditions on optical depth are applied to obtain the average extinction-to-backscatter ratio. The radius parameter is determined by comparing the measured ratio with that found from Mie scatter calculations for a variety of typical drop size distributions. This extinction-to-backscatter method was originally proposed in the literature for measuring mode radius, but at 10.6-μm wavelength the current results show better accuracy for mean or effective radius. Sources of error are discussed. A lidar probed the sides of fair-weather cumulus clouds in the first application of this method. The resulting values of effective radius were reasonable, and the expected increase of effective radius with height was observed 相似文献
17.
差分吸收激光雷达发射光束与接收视场的重叠区域用几何因子函数来描述,几何因子是差分吸收激光雷达的重要参数。提出了一种实验方法,实验使用米散射激光雷达和差分吸收激光雷达同时测量信号,通过对比分析两台激光雷达采集信号计算得到的气溶胶散射比廓线,获得差分吸收激光雷达的几何因子。该方法的优点在于不需要预先得到精确度高的激光雷达参数,比如望远镜直径,光束发散角,望远镜接收视场角等。该方法的应用有利于减少近地面差分吸收激光雷达测量臭氧廓线的误差,提高差分吸收激光雷达的探测性能,有助于研究近地面层的臭氧时空分布特征。 相似文献