A Case Study of Marine Cold Air Outbreaks with the Simple Convection-Permitting E3SM Atmosphere Model

The cloud transition associated with marine cold air outbreaks (MCAOs) presents a challenge for numerical models due to the scales of shallow convection and related mixed-phase microphysical processes being much finer than the effective resolution of these models. In this study, we evaluated the model performance of the DOE global Simple Cloud-Resolving E3SM Atmosphere Model (SCREAMv0) in simulating mesoscale variability and cloud phase partitioning during an intense MCAO event over the far northern Atlantic. SCREAMv0 captures the qualitative transition of cloud and boundary layer properties based on observations from the DOE Atmospheric Radiation Measurement program (ARM) Cold-Air Outbreaks in the Marine Boundary Layer Experiment (COMBLE) field campaigns. While the SCREAMv0 liquid water content in the cumulus cloud regime tends to be underestimated, the ice clouds might be overestimated and are strongly linked to the model-resolved updrafts.

To investigate how prescribed aerosol and simplified mixed-phase cloud microphysical processes impact cloud transition, we conducted a COMBLE case study using the Doubly Periodic mode of SCREAM (DP-SCREAM), which is a computationally efficient model configuration for process-level study. We will present DP-SCREAM results concerning the factors controlling the efficiency of the liquid-to-ice transition in mixed-phase clouds simulated by SCREAM. These factors include cloud ice particle nucleation and cloud-ice collision efficiency, different Ice Nuclei (IN) conditions, and large-scale conditions. We will use ARM COMBLE cloud observations and satellite retrievals as observational references to assess the modeled physical processes.

Acknowledgement: This work is supported by the ASR Program for the Office of Science of the U.S. DOE. This work was performed under the auspices of the U.S. DOE by LLNL under contract DE-AC52-07NA27344. LLNL-ABS-853799