Abstract
ABSTRACTThe life cycles of intense high-latitude mesoscale cyclones and polar lows are strongly shaped by their ambient environments. This study focuses on the influence of the orography of Svalbard and the sea ice cover in the Norwegian and Barents Seas on polar low development. We investigate two typical polar lows that formed near Svalbard during northerly cold-air outbreaks. Each case is simulated using the Met Office Unified Model with convection-permitting grid spacing. A series of sensitivity experiments is conducted with an artificially changed land mask, orography, and sea ice distribution. We find that Svalbard acts to block stably stratified air from the ice-covered Arctic Ocean, and as an additional source of low-level cyclonic vorticity aiding polar low genesis and intensification. A decrease in sea ice cover west of Svalbard results in a moderate intensification of the polar lows, particularly for the more convectively driven case, while an increase in the sea ice cover significantly hinders their development. These experiments exemplify that polar mesoscale cyclones in the northeast Atlantic can withstand large perturbations in the surface conditions (such as the removal of Svalbard) and still develop to sufficient intensity to be labeled as polar lows. However, there is a sensitivity to Svalbard’s orography and surrounding sea ice cover, illustrated by a clear modulation of polar low genesis and development.
Highlights
High-latitude mesoscale cyclones, and their intense subcategory polar lows (PLs), usually occur concomitantly with marine cold air outbreaks (CAOs)
During the PL event, this upper-level vortex becomes more concentrated and propagates toward the Scandinavian coast, elongating the cold anomaly over the western Norwegian Sea. This is reflected in the 500-hPa potential vorticity (PV) field (Fig. 2a), which contains an elongated maximum that moves to the region from the north
The moment when the forefront of the PV maximum happens to pass over Svalbard (Fig. 2a), an embryo of the future Synergy for Improved Forecasting of Polar Lows (STARS)-72 PL detaches from the western coast of the archipelago
Summary
High-latitude mesoscale cyclones, and their intense subcategory polar lows (PLs), usually occur concomitantly with marine cold air outbreaks (CAOs) (e.g., see Kolstad 2006). The Svalbard Archipelago is the major orographic obstacle for these CAOs in the Norwegian and Barents Seas and climatological studies (e.g., Condron et al 2006; Michel et al 2018) report a maximum of mesoscale cyclone activity in its vicinity. Michel et al (2018) suggest that no significant correlation between PL activity and sea ice extent in the North Atlantic has been observed so far. This controversy calls for more investigation of the mechanisms of cyclone interactions with the surface. We present a high-resolution modeling study of two PL events in the Norwegian Sea and examine their sensitivity to Svalbard’s orography and the sea ice distribution around it
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
