Consideration of Initial Cloud Droplet Size Distribution Shapes in Quantifying Different Entrainment‐Mixing Mechanisms. Issue 13 (28th June 2021)

• Record Type: Journal Article
• Authors: Luo, Shi; Lu, Chunsong; Liu, Yangang; Gao, Wenhua; Zhu, Lei; Xu, Xiaoqi; Li, Junjun; Guo, Xiaohao
• Is Part Of: Journal of geophysical research. Volume 126:Issue 13(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-06-28
• Subjects: Atmospheric physics -- Periodicals; Geophysics -- Periodicals; 551.5
• DOI: 10.1029/2020JD034455
• Languages: English
• ISSNs: 2169-897X

Abstract

Abstract: Entrainment‐mixing process significantly affects cloud micro/macrophysics and the evaluation of aerosol indirect effects. However, it is still an open question as to how to quantify entrainment‐mixing mechanism for broad cloud droplet size distributions (CDSDs). Here, CDSDs with different spectral widths are used to initialize the Explicit Mixing Parcel Model to address this problem, and microphysical properties are compared for different CDSD widths. For relatively broad CDSDs, as the number concentration and liquid water content decrease, the volume‐mean radius and mean radius increase, which is opposite to the scenario for relatively narrow CDSDs and the homogeneous/inhomogeneous conceptual model. For the relatively broad CDSDs, such relationships could be mistaken as inhomogeneous mixing with subsequent ascent in analysis of the conventional microphysical mixing diagram. This then causes traditional homogenous mixing degrees to be unrealistically negative and not applicable for relatively broad CDSDs. New measures are introduced to explicitly account for the effect of CDSD spectral shapes on quantifying entrainment‐mixing mechanism. The new measures yield reasonable ranges of values that conform to the dynamical measures such as the Damköhler and transitional scale numbers, and their temporal variation can be explained physically. This study extends the measures of homogeneous mixing degrees from narrow to broad CDSDs, and sheds new light on the consideration of CDSD shapes in parameterizations of entrainment‐mixing mechanism. Key Points: Microphysical properties and entrainment‐mixing mechanism are dissected for different cloud droplet spectral widths Inhomogeneous mixing with subsequent ascent could be mistakenly identified and traditional measures are not applicable for broad spectra New measures of homogeneous mixing degrees are introduced and verified