The Dynamics and Microphysics of High-Latitude Clouds during the COMBLE Field Experiment

The Cold-Air Outbreaks (CAOs) in the Marine Boundary Layer Experiment (COMBLE) was conducted successfully between December 1st, 2019 and May 31st, 2020 around the Norwegian Sea. The main objective of COMBLE is to quantify the properties of shallow convective clouds that develop as part of an air-mass transformation process when cold air blows over open water. Specifically, the experiment aims to describe the mesoscale organization of clouds and precipitation during CAOs and to investigate the dynamics, cloud properties and precipitation in boundary layer convection. COMBLE deployed the ARM Mobile Facility (AMF) #1 along the coast of northern Scandinavia, at an Arctic latitude (70°N), and an array of additional instruments on Bear Island (75°N) in the Norwegian Sea. The instruments deployed at these two sites collected a large array of in situ and remote sensing observations of atmospheric conditions, clouds, precipitation, and aerosol. The Met Norway radar network also collected data during the observational period over the Norwegian Sea whereas the CloudSat W-band radar provides contextual cloud climatology. This study focused on 13 CAO days during the 6-month observational period. The Met Norway data describe the cloud boundaries and fraction. The combined Ka-band Zenith-pointing Radar and Doppler lidar observations are used to provide the complete characterization of the vertical air motion and eddy dissipation rate above and below the cloud base. The radar/lidar and disdrometer observations are combined to delineate the type of precipitation reaching the surface. The microwave radiometer indicated the presence of vertical columns of high liquid water path which are found to be collocated with strong updrafts motions.