Why is the cloud albedo — Particle size relationship different in optically thick and optically thin clouds?
Why is the cloud albedo — Particle size relationship different in optically thick and optically thin clouds?
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为什么光学厚云和光学薄云中的云反照率 - 粒径关系不同？
DOI：
10.1029/1999gl011098
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发表时间：
2000
影响因子：
5.2
通讯作者：
Chris Tyler
中科院分区：
文献类型：
--
作者：
U. Lohmann;G. Tselioudis;Chris Tyler
最近的研究分析了卫星数据中云反照率与暖云液滴大小的关系。结果表明，对于光学厚度的海洋云（τ > 15），云的反照率随云滴有效半径（re）的减小而增大。对于光学较薄的海洋云（τ < 15），如果液态水的含量是绝热的，则云的反照率随re的增加而增加。关于τ - re关系中符号变化的假设是绝热液态水含量的偏差或单层云与多层云的存在。在这项研究中，ECHAM模型被用来检验这些假设，该模型显示了光学厚度较薄和较厚的海洋云的τ - re相关性的符号变化。τ‐re的概率密度函数表明，相关符号的变化可归因于降水云与非降水云，但不能归因于单层云与多层云的差异。
Recent studies have analyzed satellite data in terms of the relationship of cloud albedo with droplet size for warm clouds. It was found that for optically thick marine clouds (τ > 15) the cloud albedo increases with decreasing cloud droplet effective radius (re). For optically thinner marine clouds (τ < 15) cloud albedo increases with increasing re as to be expected if the liquid water content is adiabatic. Hypotheses for the change in sign in the τ ‐ re relationship are deviations from an adiabatic liquid water content or the presence of single layer versus multi layer clouds. In this study, the ECHAM model, which exhibits this sign change in the τ ‐ re correlation for optically thin and thick marine clouds, is used to test these hypotheses. Probability density functions of τ ‐ re show that the change in sign of the correlation can be attributed to precipitating versus non‐precipitating clouds, but not to the difference in single layer versus multi‐layer clouds.