Airborne Observations of Polar Low Development During the CAESAR Field Campaign

Polar lows are relatively small and short-lived marine mesoscale cyclones that can produce heavy snowfall, strong winds, and large ocean waves, all of which can wreak havoc on coastal communities and ocean operations. Forecasters are often challenged to accurately predict the strength and location of these cyclones. Polar lows are generally associated with Arctic cold-air outbreaks.

During the 2024 Cold-Air Outbreak Experiment in the Sub-Arctic Region (CAESAR) field campaign, the NSF/NCAR C-130 aircraft was deployed with an array of in-situ and remote sensing instrumentation. Here we use in situ meteorological measurements, aircraft dropsondes, the W-band Wyoming Cloud Radar (WCR), a Ka-Band Profiling Radar (KPR) and Multi-Function Airborne Raman Lidar (MARLi) pointing downward, and the Wyoming Cloud Lidar (WCL) and upward-looking 183 GHz G-Band Vapor Radiometer (GVR). This assembly of remote sensing instrumentation provided the CAESAR campaign a comprehensive insight into the thermodynamics and mixed-phase cloud microphysics. Of particular interest in this study are the high-resolution WCR reflectivity and vertical velocity data from the sea surface to cloud top, and dual-Doppler inferred along-track winds below flight level.

On April 2nd 2024 of the CAESAR campaign, a relatively shallow and broad polar low formed southwest of Svalbard in the Norwegian Sea, tracking southward toward the Norwegian coastline during an Arctic cold-air outbreak. The NSF/NCAR C-130 comprehensively characterized the intensifying polar low through a series of traverses in different directions. This presentation uses the already described in situ, dropsonde, and remotely sensed data to document the detailed cloud, thermal, and dynamical structure of the polar low, and to examine polar cyclogenesis. Factors examined include the role of the upstream terrain, shallow baroclinicity due to air masses with distinct trajectories over open water, and cloud diabatic heating.