Cloud microphysical and radiative properties for parameterization and satellite monitoring of the indirect effect of aerosol on climate
Cloud microphysical and radiative properties for parameterization and satellite monitoring of the indirect effect of aerosol on climate
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DOI：
10.1029/2002jd002682
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发表时间：
2003-04
影响因子：
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通讯作者：
J. Brenguier;H. Pawłowska;L. Schüller
中科院分区：
文献类型：
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作者：
J. Brenguier;H. Pawłowska;L. Schüller
[1]通过统计第二次气溶胶表征实验中8个案例的液滴数浓度、液滴平均体积半径和液态水含量，记录了层积云微物理场的空间变异性。从云底到云顶，在五个子层中计算统计量，并通过假设随机或最大重叠，利用它们来估计云光学厚度和液态水路径。得到的光学厚度和液态水路径的原位频率分布与从云辐射的独立遥感测量中获取的这两个参数的分布进行了验证。它们还用于测试基于液态水路径和液滴有效半径或云滴数浓度的光学厚度参数化。这一独特的数据集对云的微物理和辐射特性进行了广泛的、伴随的和独立的测量，最终用于通过检查云光学厚度和雾滴有效半径之间的相关性来评估气溶胶间接效应的可探测性。如果只考虑几何厚度可比较值的情况，则光学厚度与有效半径之间的相关性为负，正如Twomey[1977]所预测的那样。然而，如果污染最严重的病例也被考虑在内，趋势表明两者呈正相关。事实上，在ACE-2期间采样的污染最严重的云系统比海洋和中间情况稍微干燥，因此更薄，因此光学厚度和液滴有效半径之间存在正相关关系。本研究表明，利用卫星观测监测气溶胶间接效应需要独立检索液态水路径以及云光学厚度和液滴有效半径。
[1] The spatial variability of the microphysical fields in stratocumulus clouds is documented in this paper with statistics of droplet number concentration, droplet mean volume radius, and liquid water content for eight cases of the second Aerosol Characterization Experiment. Statistics are calculated in five sublayers, from cloud base to cloud top, and they are utilized for deriving estimates of cloud optical thickness and liquid water path, by assuming either random or maximum overlap. The resulting in situ frequency distributions of optical thickness and liquid water path are validated against distributions of these two parameters retrieved from independent remote sensing measurements of cloud radiances. They are also used for testing parameterizations of optical thickness based on liquid water path and either the droplet effective radius or the cloud droplet number concentration. This unique data set of extensive, concomitant, and independent measurements of cloud microphysical and radiative properties is finally used for assessing the detectability of the aerosol indirect effect through examination of the correlation between cloud optical thickness and droplet effective radius. If only cases of comparable values of geometrical thickness are considered, the correlation between optical thickness and effective radius is negative, as anticipated by Twomey [1977]. However, if the most polluted cases are also accounted for, the trend suggests a positive correlation. In fact, the most polluted cloud systems sampled during ACE-2 were slightly drier, hence thinner, than the marine and intermediate cases, hence producing a positive correlation between optical thickness and droplet effective radius. This study demonstrates that the monitoring of the aerosol indirect effect with satellite observations requires an independent retrieval of the liquid water path together with the cloud optical thickness and droplet effective radius.