An improved algorithm of cloud droplet size distribution from POLDER polarized measurements
An improved algorithm of cloud droplet size distribution from POLDER polarized measurements
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POLDER 偏振测量云滴尺寸分布的改进算法
DOI：
10.1016/j.rse.2019.04.013
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发表时间：
2019-07
影响因子：
13.5
通讯作者：
Chen Liangfu
中科院分区：
文献类型：
--
作者：
Shang Huazhe;Letu Husi;Breon Francois-Marie;Riedi Jerome;Ma Run;Wang Ziming;Nakajima Takashi Y.;Wang Zhongting;Chen Liangfu
地球反射率偏振和方向性（POLDER）仪器提供独特的云滴半径（CDR）和有效方差（EV）观测，用于全球范围内的云分析。然而，传统的POLDER算法对云滴尺度分布的估计受到空间分辨率（150 km）较低和对大云滴（CDR > 15 μm）信息不足的限制。在这项研究中，我们提出了一种改进的初级云弓检索（PCR）算法估计CDR和EV从POLDER。基于辐射传输模型的模拟反演表明，主要的云弓测量是敏感的大液滴（CDR > 15 μm），使反演应用在一个更高的空间分辨率，因此，我们采用POLDER偏振测量从主要和额外的云弓区域的PCR算法。使用POLDER测量的检索案例表明，当云场是均匀的时，PCR算法是稳健的。当云场不均匀时，CDR的估计对散射角范围和网格尺寸敏感，不确定度小于1 μm。此外，根据反演网格大小与总成功反演之间的关系，40-60 km的空间分辨率适合于PCR算法。利用2008年2月、5月、8月和11月的POLDER观测数据，对全球范围内的PCR反演结果与业务产品进行了进一步的比较，结果表明，全球范围内的PCR反演结果与业务产品一致，CDR < 15 μm。我们的分析表明，大多数的大液滴估计使用传统的程序是高估了由于缺乏主要的云弓测量。PCR算法可以扩大CDR（3-25 μm）和EV（0.01-0.29）的估计范围，提高反演分辨率（40-60 km）。
The Polarization and Directionality of Earth Reflectances (POLDER) instrument provides unique cloud droplet radius (CDR) and effective variance (EV) observations for the analysis of clouds on the global scale. However, the cloud droplet size distribution estimated using the conventional POLDER algorithm is limited by its coarse spatial resolution (150 km) and insufficient information for large droplets (CDR > 15 μm). In this study, we proposed an improved primary cloudbow retrieval (PCR) algorithm to estimate CDR and EV from POLDER. Simulated retrievals based on a radiative transfer model indicate that primary cloudbow measurements are sensitive to large droplets (CDR > 15 μm) and enable the retrieval to be applied at a higher spatial resolution; therefore, we employ POLDER polarized measurements from both primary and supernumerary cloudbow regions in the PCR algorithm. Retrieval cases using POLDER measurements reveal that the PCR algorithm is robust when the cloud fields are homogeneous. When the cloud field is heterogeneous, the estimation of CDR is sensitive to the scattering angle ranges as well as the grid size, with uncertainty <1 μm. In addition, a spatial resolution of 40–60 km is suitable for the PCR algorithm based on the relationship between the retrieval grid size and the total successful retrievals. Further comparisons between the PCR retrievals and operational products are conducted on the global scale using POLDER measurements for February, May, August and November 2008, revealing that PCR retrievals agree well with operational products on the global scale as CDR < 15 μm. Our analysis indicates that most of the large droplets estimated using the conventional procedure are overestimated due to the absence of primary cloudbow measurements. The PCR algorithm permits an extended range of CDR (3–25 μm) and EV (0.01–0.29) estimates and a higher resolution (40–60 km) in the retrieval.
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影响因子：
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作者：
S. Yum;J. Hudson
通讯作者：
S. Yum;J. Hudson
影响因子：
6.3
作者：
J. Riedi;B. Marchant;S. Platnick;B. Baum;F. Thieuleux;C. Oudard;F. Parol;J. Nicolas;P. Dubuisson
通讯作者：
J. Riedi;B. Marchant;S. Platnick;B. Baum;F. Thieuleux;C. Oudard;F. Parol;J. Nicolas;P. Dubuisson
影响因子：
5.2
作者：
Breon, FM;Goloub, P
通讯作者：
Goloub, P
影响因子：
6.3
作者：
M. Juárez;A. Davis;E. Fetzer
通讯作者：
M. Juárez;A. Davis;E. Fetzer
影响因子：
5.2
作者：
L. Di Girolamo;L. Liang;S. Platnick
通讯作者：
L. Di Girolamo;L. Liang;S. Platnick