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Vertical structure of clouds and precipitation during Arctic cold-air outbreaks and warm-air intrusions: observations from COMBLE
  • +2
  • Christian Philipp Lackner,
  • Bart Geerts,
  • Timothy W Juliano,
  • Lulin Xue,
  • Branko Kosović
Christian Philipp Lackner
University of Wyoming
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Bart Geerts
University of Wyoming

Corresponding Author:[email protected]

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Timothy W Juliano
National Center for Atmospheric Research
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Lulin Xue
National Center for Atmospheric Research (UCAR)
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Branko Kosović
National Center for Atmospheric Research
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Abstract

The Arctic is marked by deep intrusions of warm, moist air, alternating with outbreaks of cold air down to lower latitudes. The typical vertical structure of clouds and precipitation during these two synoptic weather extremes is examined at a coastal site at 69°N in Norway. The Norwegian Sea is a corridor for warm-air intrusions (WAIs) and frequently witnesses cold-air outbreaks (CAOs). This study uses data from profiling radar, lidar, and microwave radiometer, radiosondes and other probes that were collected during the Cold air Outbreaks in the Marine Boundary Layer Experiment (COMBLE) between 1 December 2019 and 31 May 2020. Marine CAOs are defined in terms of thermal instability relative to the sea surface temperature, and warm-air intrusions in terms of stratification of moist static energy between the surface and 850 hPa. Cloud structures in CAOs are convective, driven by strong surface heat fluxes over a long fetch of open water, with cloud tops between 2-4 km. The mostly open-cellular convection may contain substantial ice and produce intermittent moderate precipitation at the observational site, notwithstanding the low precipitable water vapor. In contrast, WAIs are marked by high values of precipitable water vapor and integrated vapor transport. WAI clouds are stratiform, with cloud tops often exceeding 6 km, sometimes layered, and generally producing persistent precipitation that can be heavier than in CAOs.