Profiling cloud ice mass and particle characteristic size from Doppler radar measurements
Profiling cloud ice mass and particle characteristic size from Doppler radar measurements
复制标题
通过多普勒雷达测量分析云冰质量和颗粒特征尺寸
DOI：
10.1175/1520-0426(2002)019
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发表时间：
2002
影响因子：
2.2
通讯作者：
A. Heymsfield
中科院分区：
文献类型：
--
作者：
S. Matrosov;A. Korolev;A. Heymsfield
提出了一种利用垂直点云雷达从地面雷达反射率和多普勒速度测量数据中反演冰云微物理参数垂直剖面的遥感方法。该方法将时间平均多普勒速度（用作反射加权粒子下落速度的代理）与粒子特征尺寸（如中位数或平均值）联系起来。有了粒子特征尺寸的估计剖面，然后利用反射率测量计算云冰水含量（IWC）的剖面。该方法考虑了颗粒尺寸和下落速度-尺寸关系参数之间的内在相关性。它还解释了颗粒体积密度随粒径的变化。该方法的适用范围包括冰相云和含有液滴的混合相云，液滴与冰粒相比较小，因此雷达信号以这些较大的颗粒为主。然而，它仅限于没有强烈上升和下降气流的观测情况，因此平均垂直空气运动的残差与反射加权云粒子下降速度相比足够小。应用多普勒速度反射率法对8.6 mm波长雷达观测北极云层时获得的数据进行了分析。典型的颗粒特征尺寸检索不确定性约为35% - 40%，IWC检索不确定性约为60% - 70%，但在某些情况下，IWC的不确定性可高达2倍（即250%，1100%）。与一个观测病例的原位数据比较，检索到的特征尺寸和IWC估计值与原位估计值分别相差25%和55%。利用遥感方法获得的微物理检索结果与利用雷达-红外辐射计组合测量的多传感器技术获得的数据进行了比较。对于未被液体云遮挡的纯冰相层（即适用多传感器方法的条件），两种遥感方法的平均粒径结果的相对标准偏差约为27%，IWC的相对标准偏差约为38%，相对偏差分别仅为5%和20%。
A remote sensing method is proposed for the retrievals of vertical profiles of ice cloud microphysical parameters from ground-based measurements of radar reflectivity and Doppler velocity with a vertically pointed cloud radar. This method relates time-averaged Doppler velocities (which are used as a proxy for the reflectivity-weighted particle fall velocities) to particle characteristic sizes such as median or mean. With estimated profiles of particle characteristic size, profiles of cloud ice water content (IWC) are then calculated using reflectivity measurements. The method accounts for the intrinsic correlation between particle sizes and parameters of the fall velocity‐size relations. It also accounts for changes of particle bulk density with size. The range of applicability of this method encompasses ice-phase clouds and also mixed-phase clouds that contain liquid drops, which are small compared to ice particles, so the radar signals are dominated by these larger particles. It is, however, limited to the observational situations without strong up- and downdrafts, so the residual of mean vertical air motions is small enough compared to the reflectivity-weighted cloud particle fall velocities. The Doppler-velocity reflectivity method was applied to the data obtained with an 8.6-mm wavelength radar when observing Arctic clouds. Typical retrieval uncertainties are about 35%‐40% for particle characteristic size and 60%‐70% for IWC, though in some cases IWC uncertainties can be as high as factor of 2 (i.e., 250%, 1100%). Comparisons with in situ data for one observational case yielded 25% and 55% differences in retrieved and in situ estimates of characteristic size and IWC, respectively. The results of the microphysical retrievals obtained from the remote sensing method developed here were compared with data obtained from the multisensor technique that utilizes combined radar‐ IR radiometer measurements. For pure ice-phase layers unobstructed by liquid clouds (i.e., conditions where the multisensor approach is applicable), the relative standard deviations between the results of both remote sensing approaches were about 27% for mean particle size and 38% for IWC, with relative biases of only 5% and 20%, respectively.