Quantifying the Relationship between Turbulent Mixing Mechanisms and Spectral Shape of Cloud Droplet Size Distribution

Description

Different turbulent mixing mechanisms can occur in clouds, depending on the time scales of turbulent mixing and droplet population response. And it is generally recognized that different mixing processes may lead to striking differences in the spectral shape of the cloud droplet size distribution in addition to droplet concentration and liquid water content. However, the quantitative relationship between mixing mechanisms and spectral shape of the cloud droplet size distribution remain elusive, due probably to lacking a unified measure of the variety of different mixing mechanisms. In this study, we take advantage of a new unified measure of different mixing types (homogeneous mixing degree), and examine its relationship to the spectral shape of the cloud droplet size distribution by combining the approaches of theoretical, modeling, and observational analyses. Three measures of the spectral shape of the cloud droplet size distribution (standard deviation, relative dispersion, and skewness) will be examined. The skewness measure will inform us of the direction of spectral broadening (or narrowing). The results will shed new light on the important yet understudied relationship. Furthermore, the results will provide much-needed physical insights into accurately parameterizing turbulent mixing mechanisms and spectral shape of the cloud droplet size distribution in various models, including large-eddy simulation models and climate models.