Response of mixed-phase boundary layer clouds with rapid and slow ice nucleation processes to cloud-top temperature trend

Wednesday, 16 December 2015: 17:15
3004 (Moscone West)
Ann M Fridlind1, Alexander Avramov2, Andrew S Ackerman1, Peter Aaron Alpert3 and Daniel Alexander Knopf3, (1)NASA Goddard Institute for Space Studies, New York, NY, United States, (2)Massachusetts Institute of Technology, Cambridge, MA, United States, (3)Stony Brook University, Institute for Terrestrial and Planetary Atmospheres / School of Marine and Atmospheric Sciences, Stony Brook, NY, United States
It has been argued on the basis of some laboratory data sets, observed mixed-phase cloud systems, and numerical modeling studies that weakly active or slowly consumed ice forming nuclei (IFN) may be important to natural cloud systems. It has also been argued on the basis of field measurements that ice nucleation under mixed-phase conditions appears to occur predominantly via a liquid-phase mechanism, requiring the presence of liquid droplets prior to substantial ice nucleation. Here we analyze the response of quasi-Lagrangian large-eddy simulations of mixed-phase cloud layers to IFN operating via a liquid-phase mode using assumptions that result in either slow or rapid depletion of IFN from the cloudy boundary layer. Using several generalized case studies that do not exhibit riming or drizzle, based loosely on field campaign data, we vary environmental conditions such that the cloud-top temperature trend varies. One objective of this work is to identify differing patterns in ice formation intensity that may be distinguishable from ground-based or satellite platforms.