UV Raman lidar measurements of relative humidity for the characterization of cirrus cloud microphysical properties
UV Raman lidar measurements of relative humidity for the characterization of cirrus cloud microphysical properties
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DOI：
10.5194/acp-9-8799-2009
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发表时间：
2009-11
影响因子：
6.3
通讯作者：
P. Girolamo;D. Summa;R. Lin;T. Maestri;R. Rizzi;G. Masiello
中科院分区：
文献类型：
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作者：
P. Girolamo;D. Summa;R. Lin;T. Maestri;R. Rizzi;G. Masiello
抽象的。讨论了拉曼激光雷达系统 BASIL 在波坦察在存在卷云的情况下进行的拉曼激光雷达测量。测量于 2004 年 9 月 6 日在 EAQUATE 实验意大利阶段的框架内进行。 BASIL 的主要特点是能够基于旋转和振动拉曼激光雷达技术在紫外线中的应用，在白天和夜间对大气温度和水蒸气以及相对湿度进行高分辨率和精确测量。 BASIL 还能够提供粒子反向散射和消光系数的测量，以及激光雷达比（在进行这些测量时，仅在一种波长下），这对于推断云的几何和微物理特性至关重要。讨论了一个案例研究，以评估拉曼激光雷达测量卷云（云下方和云内部）湿度的能力。虽然观察到云层内的空气相对于水始终处于欠饱和状态，但在这些云内部发现了冰过饱和和欠饱和条件。在下云层下方观察到上层对流层湿润。协同使用来自地面拉曼激光雷达的数据和 NAST-I 机载光谱仪测量的光谱辐射率，可以确定由于卷云的存在而导致的大气冷却/加热速率的时间演变。卷云层下方的激光雷达测量结果已使用具有显式微物理原理的一维卷云模型进行了解释。一维模拟表明，沉积润湿对潮湿异常有显着贡献，但其他机制也有贡献。这一结果支持了这样的假设：观测到的对流层中部增湿是一个真实的特征，它受到沉淀冰晶升华的强烈影响。本研究中所示的结果表明，拉曼激光雷达（如本研究中使用的拉曼激光雷达）可以解析研究卷云微物理过程所需的空间和时间尺度，并且足够灵敏，可以揭示和量化与卷云升华相关的上层对流层加湿。
Abstract. Raman lidar measurements performed in Potenza by the Raman lidar system BASIL in the presence of cirrus clouds are discussed. Measurements were performed on 6 September 2004 in the frame of the Italian phase of the EAQUATE Experiment. The major feature of BASIL is represented by its capability to perform high-resolution and accurate measurements of atmospheric temperature and water vapour, and consequently relative humidity, both in daytime and night-time, based on the application of the rotational and vibrational Raman lidar techniques in the UV. BASIL is also capable to provide measurements of the particle backscatter and extinction coefficient, and consequently lidar ratio (at the time of these measurements, only at one wavelength), which are fundamental to infer geometrical and microphysical properties of clouds. A case study is discussed in order to assess the capability of Raman lidars to measure humidity in presence of cirrus clouds, both below and inside the cloud. While air inside the cloud layers is observed to be always under-saturated with respect to water, both ice super-saturation and under-saturation conditions are found inside these clouds. Upper tropospheric moistening is observed below the lower cloud layer. The synergic use of the data derived from the ground based Raman Lidar and of spectral radiances measured by the NAST-I Airborne Spectrometer allows the determination of the temporal evolution of the atmospheric cooling/heating rates due to the presence of the cirrus cloud. Lidar measurements beneath the cirrus cloud layer have been interpreted using a 1-D cirrus cloud model with explicit microphysics. The 1-D simulations indicate that sedimentation-moistening has contributed significantly to the moist anomaly, but other mechanisms are also contributing. This result supports the hypothesis that the observed mid-tropospheric humidification is a real feature which is strongly influenced by the sublimation of precipitating ice crystals. Results illustrated in this study demonstrate that Raman lidars, like the one used in this study, can resolve the spatial and temporal scales required for the study of cirrus cloud microphysical processes and appear sensitive enough to reveal and quantify upper tropospheric humidification associated with cirrus cloud sublimation.