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基于三波长拉曼-米散射激光雷达的武汉地区卷云粒子光学参数特征

Optical parameters of cirrus particles in Wuhan based on three-wavelength Raman-Mie scattering lidar

  • 摘要: 为识别卷云光学特征,基于2023年10—12月武汉国家基本气象站三波长拉曼-米散射激光雷达的连续探测资料,选取武汉地区2023年11月一次典型卷云过程为例进行分析。结果表明,此次卷云过程中卷云平均云底高度为7.0 km,并呈现夜间缓慢降低、白天逐渐升高的变化趋势,期间355 nm、532 nm平均雷达比分别为40.6 Sr和59.3 Sr。结合后向散射系数和退偏振比识别卷云粒子相态,过程中云底和云顶三个波长间后向散射系数差异小,且退偏振比在0.35以上,以非球形大粒子为主,而云内355 nm和532 nm后向散射系数明显高于1 064 nm,且退偏振比较小,多为球形小粒子,云团自下而上表现出冰晶-过冷水-冰晶的结构分布特征。

     

    Abstract: To identify the optical characteristics of cirrus clouds, this study analyzed a typical cirrus event in Wuhan in November 2023 based on the continuous observation data from a triple-wavelength Raman-Mie scattering lidar at Wuhan National Basic Meteorological Station from October to December 2023. The results are as follows. The average cloud base height of cirrus during this event was 7.0 km, and it showed a trend of slowly decreasing at night and gradually increasing during the daytime. During this period, the average lidar ratios at 355 nm and 532 nm were 40.6 Sr and 59.3 Sr, respectively. The phases of cirrus particles were identified by combining the backscattering coefficient and depolarization ratio. Small differences in backscattering coefficients across the three wavelengths at the cloud base and the cloud top were found, and the depolarization ratios were above 0.35, suggesting the dominance of non-spherical large particles during this event. However, the backscattering coefficients at 355 nm and 532 nm in the cloud were significantly higher than at 1 064 nm with smaller depolarization ratios, indicating more spherical small particles in the cloud. The vertical structure of the cirrus showed an ice crystal-supercooled water-ice crystal distribution characteristic from the bottom to the top.

     

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