CAOs versus WAIs: Profiling data from the AMF1 site in COMBLE

Submitter:

Geerts, Bart — Department of Atmospheric Science, University of Wyoming
Lackner, Christian Philipp — University of Wyoming

Area of research:

Cloud Distributions/Characterizations

Journal Reference:

Lackner C, B Geerts, T Juliano, L Xue, and B Kosovic. 2023. "Vertical Structure of Clouds and Precipitation During Arctic Cold‐Air Outbreaks and Warm‐Air Intrusions: Observations From COMBLE." Journal of Geophysical Research: Atmospheres, 128(13), e2022JD038403, 10.1029/2022JD038403.

Science

Atmospheric profiling data collected at the COMBLE ANX site, a coastal site at 69°N in Norway, is investigated.
Vertical velocity, cloud, and precipitation structures are fundamentally different in marine cold-air outbreaks (CAOs) versus in warm-air intrusions (WAIs).

Impact

The Arctic, more so than Antarctica, is marked by deep intrusions of warm, moist air, alternating with outbreaks of cold air down to lower latitudes. These heat exchanges between the Arctic and lower latitudes are key to understanding the observed and predicted Arctic amplification, i.e., the accelerated climate warming in the Arctic. The Norwegian Sea is a corridor for warm-air intrusions into the Arctic. At the same time, it frequently witnesses cold-air outbreaks, which in extreme events can be hazardous to maritime activities. Here we examine the typical vertical structure of the updrafts, clouds, and precipitation during these two weather types, using six months of data collected during the ARM Cold-Air Outbreaks in the Marine Boundary Layer Experiment (COMBLE).

Summary

The main findings of this study are: (a) the cold-air outbreak cloud regime is convective, driven by strong surface heat fluxes over a long fetch of open water. Clouds are rather low-topped, yet they do produce precipitation. (b) warm-air intrusions are marked by enhanced water vapor, high vapor transport, and clouds driven by deep frontal weather systems generally producing persistent precipitation.