Cloud processing, cloud evaporation and Angström exponent
Cloud processing, cloud evaporation and Angström exponent
复制标题
云处理、云蒸发和 Angström 指数
DOI：
--
复制
发表时间：
2008
期刊：
影响因子：
--
通讯作者：
V. Kamphuis
中科院分区：
文献类型：
--
作者：
G. Roelofs;V. Kamphuis
通过一个云团模式，我们研究了云处理和云蒸发如何改变气溶胶种群的大小分布和Angstr‘om指数。我们的研究为观测到的云附近气溶胶光学厚度和Angstrex-Ponent的变化提供了新的解释。云处理导致气溶胶颗粒浓度的降低，在粗略模式下相对最有效，并减少气溶胶分布的相对弥散。其结果是气溶胶的Angstr-om指数增大。Angstr‘om指数对云蒸发过程中相对湿度的变化非常敏感，特别是在90%-100%之间。此外，动力学限制延迟了相对大的云滴的蒸发，特别是在粗模比例相对较大的清洁和轻度污染的环境中。这是气溶胶光学厚度、Angstrexponent和环境相对湿度之间的直接关系，这可能会严重复杂化对这些参数在气溶胶性质方面的解释，例如精细模式分数。
With a cloud parcel model we investigate how cloud processing and cloud evaporation modify the size dis- tribution and the Angstr ¨ om exponent of an aerosol popula- tion. Our study provides a new explanation for the observed variability of the aerosol optical thickness and Angstrex- ponent in the vicinity of clouds. Cloud processing causes a decrease of aerosol particle concentrations, relatively most efficiently in the coarse mode, and reduces the relative dis- persion of the aerosol distribution. As a result the Angstr ¨ om exponent of the aerosol increases. The Angstr ¨ om exponent is very sensitive for changes in relative humidity during cloud evaporation, especially between 90% and 100%. In addition, kinetic limitations delay evaporation of relatively large cloud drops, especially in clean and mildly polluted environments where the coarse mode fraction is relatively large. This ham- pers a direct relation between the aerosol optical thickness, the Angstrexponent and the ambient relative humidity, which may severely complicate interpretation of these pa- rameters in terms of aerosol properties, such as the fine mode fraction.