Ground‐based remote sensing measurements from the Atmospheric Radiation Measurement Program (ARM) West Antarctic Radiation Experiment (AWARE) campaign at the McMurdo station and the ARM North Slope of Alaska (NSA) Utqiaġvik site are used to retrieve and analyze single‐layer stratiform mixed‐phase cloud macrophysical and microphysical properties for these different polar environments. Single‐layer stratiform mixed‐phase clouds have annual frequencies of occurrence of ~14.7% at Utqiaġvik and ~7.3% at McMurdo, with the highest occurrences in early autumn. Compared to Utqiaġvik, stratiform mixed‐phase clouds at McMurdo have overall higher and colder cloud‐tops, thicker ice layer depth, thinner liquid‐dominated layer depth, and smaller liquid water path. These properties show clear seasonal variations. Supercooled liquid fraction at McMurdo is greater than at Utqiaġvik because, at a given temperature, McMurdo clouds have comparable liquid water paths but smaller ice water paths. Analyses of retrieved cloud microphysical properties show that compared to Utqiaġvik, stratiform mixed‐phase clouds at McMurdo have greater liquid droplet number concentration, smaller layer‐mean effective radius, and smaller ice water content and ice number concentration at a given cloud‐top temperature. These relationships may be related to different aerosol loading and chemical composition, and environment dynamics. Results presented in this study can be used as observational constraints for model representations of stratiform mixed‐phase clouds.
In this study, we conduct sensitivity experiments with the Community Atmosphere Model version 5 to understand the impact of representing heterogeneous distribution between cloud liquid and ice on the phase partitioning in mixed‐phase clouds through different perturbations on the Wegener‐Bergeron‐Findeisen (WBF) process. In two experiments, perturbation factors that are based on assumptions of pocket structure and the partial homogeneous cloud volume derived from the High‐performance Instrumented Airborne Platform for Environmental Research (HIAPER) Pole‐to‐Pole Observation (HIPPO) campaign are utilized. Alternately, a mass‐weighted assumption is used in the calculation of WBF process to mimic the appearance of unsaturated area in mixed‐phase clouds as the result of heterogeneous distribution. Model experiments are tested in both single column and weather forecast modes and evaluated against data from the U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Program's Mixed‐Phase Arctic Cloud Experiment (M‐PACE) field campaign and long‐term ground‐based multisensor measurements. Model results indicate that perturbations on the WBF process can significantly modify simulated microphysical properties of Arctic mixed‐phase clouds. The improvement of simulated cloud water phase partitioning tends to be linearly proportional to the perturbation magnitude that is applied in the three different sensitivity experiments. Cloud macrophysical properties such as cloud fraction and frequency of occurrence of low‐level mixed‐phase clouds are less sensitive to the perturbation magnitude than cloud microphysical properties. Moreover, this study indicates that heterogeneous distribution between cloud hydrometeors should be treated consistently for all cloud microphysical processes. The model vertical resolution is also important for liquid water maintenance in mixed‐phase clouds.
more » « less- NSF-PAR ID:
- 10366384
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Atmospheres
- Volume:
- 124
- Issue:
- 23
- ISSN:
- 2169-897X
- Page Range / eLocation ID:
- p. 13071-13090
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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