Surface, aerosol, and meteorological controls on Arctic boundary layer clouds: Observations and simulations from MOSAiC and COMBLE

The Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) program’s Multidisciplinary Drifting Observatory for the Study of Arctic Climate (MOSAiC) and Cold-Air Outbreaks in the Marine Boundary Layer Experiment (COMBLE) field campaigns fill a critical observation gap in sea ice, meteorological, and cloud property measurements. MOSAiC and COMBLE collected extensive data on cloud properties, aerosols

aerosols

Small particles or droplets, such as wildfire smoke, volcanic gases, or salty sea spray, that float in the air. They are emitted by both natural events and human activities.

Source: NASA Global Climate Change Source

and boundary layer properties over the polar ice and as cold air transitions from the ice to open water. These measurements offer a pathway to improve our understanding of the Arctic cloud life cycle, which is critical for improving our understanding of Arctic climate and for future application in climate models. We will use observational datasets collected aboard the Polarstern during MOSAiC to represent conditions over the sea ice, as well as COMBLE data collected at Andenes and Bear Island to represent how air masses and clouds evolved. A novelty of MOSAiC and COMBLE data are the extensive number of instruments deployed including a ceilometer, lidar, microwave radiometer, cloud radar, total sky imager, and shipborne cloud and aerosol particle counter. These observations enable a robust and comprehensive characterization of arctic cloud and precipitation properties, supplemented by available meteorological information such as temperature, relative humidity, wind direction and wind speed. The synergy of cloud and meteorological measurements from these platforms will enable calculation of many properties for characterizing Arctic boundary layer processes. In addition to these observations, the NCAR team will build upon its recent experiences using Lagrangian (i.e., large-scale) particle-based microphysics (a.k.a. “the superdroplet method”; SDM) to test hypotheses on the role of cloud, aerosol, and boundary layer processes on Arctic cloud evolution. The SDM provides unprecedented fidelity for simulating cloud microphysics and cloud-aerosol interactions. The SDM allows for truly multi-scale simulations by incorporating physically-based representations of, for example, ice particle growth and transport that will be extended to mixed-phase and ice clouds. We will utilize a state-of-the-art community large eddy simulation (LES) model (NCAR’s Cloud Model 1; CM1) with SDM in conjunction with the observations to test our overarching hypothesis that while aerosol effects are notable, tropospheric state and surface fluxes

flux

The amount of some type of particle or energy crossing a unit area per unit time.

Source: NRC Library Source

more strongly control Arctic planetary boundary layer

planetary boundary layer

The lowest layer of the troposphere where wind is influenced by friction.

Source: National Weather Service Source

cloud properties. This project will also provide significant impetus for the advancement of large-scale cloud microphysics in community models.