Scale Dependence of Entrainment-Mixing Mechanisms in the Stratocumulus Clouds during ACE-ENA

 

Authors

Chunsong Lu — Nanjing University of Information Science and Technology
Yangang Liu — Brookhaven National Laboratory
Fan Mei — Pacific Northwest National Laboratory

Category

Microphysics (cloud, aerosol and/or precipitation)

Description

Entrainment-mixing processes are essential to the evaluation of aerosol indirect effects, warm-rain initiation, and cloud-climate feedbacks. A major challenge confronting the study of entrainment-mixing processes is that the related processes occur over a tremendous range of scales, from a cloud size down to the Kolmogorov microscale. This work examines non-drizzling stratocumulus clouds collected during the Aerosol and Cloud Experiments in the Eastern North Atlantic (ACE-ENA) to study the scale dependence of entrainment-mixing mechanisms. Two contrasting types of scale dependence are found. One type is similar to our previous finding that entrainment-mixing becomes more inhomogeneous with an increasing average time window. The other type is contrasting and a big surprise, whereby entrainment mixing mechanism changes from extremely inhomogeneous to homogeneous with an increasing average time window. A simple model is developed to figure out the main factors affecting the scale dependence of entrainment-mixing mechanism. It is found that the droplet size near dry air is the main factor affecting the scale dependence of entrainment-mixing mechanism; the scale dependence is also related to dry air size and relative humidity in the environment.