CALIPSO observations of near‐cloud aerosol properties as a function of cloud fraction
CALIPSO observations of near‐cloud aerosol properties as a function of cloud fraction
复制标题
作为云分数函数的近云气溶胶特性的 CALIPSO 观测
DOI：
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发表时间：
2014
期刊：
影响因子：
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通讯作者：
R. Wood
中科院分区：
文献类型：
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作者：
Weidong Yang;A. Marshak;T. Várnai;R. Wood
本文利用星载激光雷达资料研究了衰减后向散射的近云气溶胶统计数据与云量的关系。对亚速尔群岛周围大区域的模拟结果表明：(1)远云气溶胶统计主要来自云分数较低的场景，而近云气溶胶统计主要来自云分数较高的场景；(2)对于任何云分数，近云后向散射的增强都发生，但在云分数较高时最为明显；(3)在距云5 公里范围内，不同云分数的增强差异最显著；(4)近云增强可以用云分数和云距离的对数函数来很好地近似。这些发现表明，如果不考虑用于综合气溶胶统计的场景中云量的可变性，采样伪影将影响作为到云的距离的函数计算的这些统计。对于这里研究的亚速尔群岛地区数据集，这种伪影主要发生在距离云5 公里的范围内，并将激光雷达后向散射和颜色比的近云增强夸大了约30%。这表明，为了准确描述气溶胶性质随到云距离的变化而发生的变化，重要的是考虑云量变化的影响。
This paper uses spaceborne lidar data to study how near‐cloud aerosol statistics of attenuated backscatter depend on cloud fraction. The results for a large region around the Azores show that (1) far‐from‐cloud aerosol statistics are dominated by samples from scenes with lower cloud fractions, while near‐cloud aerosol statistics are dominated by samples from scenes with higher cloud fractions; (2) near‐cloud enhancements of attenuated backscatter occur for any cloud fraction but are most pronounced for higher cloud fractions; (3) the difference in the enhancements for different cloud fractions is most significant within 5 km from clouds; (4) near‐cloud enhancements can be well approximated by logarithmic functions of cloud fraction and distance to clouds. These findings demonstrate that if variability in cloud fraction across the scenes used for composite aerosol statistics is not considered, a sampling artifact will affect these statistics calculated as a function of distance to clouds. For the Azores region data set examined here, this artifact occurs mostly within 5 km from clouds and exaggerates the near‐cloud enhancements of lidar backscatter and color ratio by about 30%. This shows that for accurate characterization of the changes in aerosol properties with distance to clouds, it is important to account for the impact of changes in cloud fraction.