Cold-Air Outbreaks in the Marine Boundary Layer Experiment (COMBLE)

1 January 2020 - 31 May 2020

Lead Scientist: Bart Geerts

Observatory: AMF, ANX

The main objective for the proposed deployment of the ARM Mobile Facility is to quantify the properties of boundary layer convection (BLC) and air-mass transformations in cold-air outbreaks (CAO) over open water in the Arctic. COMBLE will involve the deployment of the AMF1 and a satellite site to the far North Atlantic. The AMF will be deployed near Andenes, a town on an island in Northeastern Norway, while a reduced set of instruments will be deployed on Bear Island, located approximately mid-way between the Norway mainland and Svalbard. Specifically, COMBLE aims to:

  • describe and quantify the fetch-dependent mesoscale organization and the vertical structure of BLC, including vertical profiles of vertical velocity and turbulence in convection, cloud liquid water and ice mass concentrations, cloud particle sizes, phases and shapes, and fluxes of surface heat, moisture, and radiation;
  • examine the impact of varying aerosol conditions in the upstream Arctic boundary layer, as well as marine aerosol sources and anthropogenic pollution, on these distributions and on ice initiation and snow growth processes in a range of wind and temperature regimes;
  • evaluate ground-based remote sensing observations performed with the ARM mobile facility with accompanying aircraft measurements, and broaden the ARM point observations of CAO to the regional scale using those airborne measurements, as detailed below; and
  • provide integrated data sets of dynamical, thermodynamic, and microphysical characteristics of CAO boundary layer, including clouds and aerosol properties, that will enable constraining high-resolution numerical simulations, developing process-level understanding of BLC, and, subsequently, evaluating and improving representations of shallow convection in cold-air outbreaks in weather and climate models.

Complimentary objectives enabled by this AMF deployment:

  • examine the vertical structure of developing polar lows;
  • examine orographic modification of BLC and the impact of BLC on precipitation in downwind coastal areas.


Steven Abel Ann Fridlind Mikhail Ovchinnikov
Andrew Ackerman Andreas Herber Michael Tjernstrom
Alan Blyth Michael Jensen Yonggang Wang
Tom Choularton Pavlos Kollias Manfred Wendisch
Susanne Crewell Greg McFarquhar Lulin Xue
Paul Field Roel Neggers

Related Publications


Geerts B. 2019. Cold-Air Outbreaks in the Marine Boundary Layer Experiment (COMBLE) Science Implementation Plan. Ed. by Robert Stafford, ARM user facility. DOE/SC-ARM-19-002.

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