Quantifying entrainment-mixing mechanisms for different initial cloud droplet size distribution shapes

Abstract:

Entrainment-mixing processes have significant effects on aerosol-cloud interactions, warm-rain initiation, etc. Quantitative description of homogeneous mixing degree is critical to improve parameterization of entrainment-mixing mechanisms in models. However, most studies explicitly or implicitly assume monodisperse initial cloud droplet size distribution (CDSD). The homogeneous mixing degree defined for monodisperse CDSD is not applicable for different initial CDSD shapes.

To overcome this weakness, new homogeneous mixing degree weighted by CDSD is defined based on the Explicit Mixing Parcel Model simulations. First, the new homogeneous mixing degree is consistent with the traditional one when CDSD is monodisperse. Second, the relationships between the new homogeneous mixing degree and Damköhler number also prove the rationality of the new homogeneous mixing degree. Third, the effects of relative humidity, number concentration, and turbulent dissipation rate on the new homogeneous mixing degree is consistent with the traditional one.