Modulation of North Atlantic Polar Low Activity by Sudden Stratospheric Warmings (SSWs)

Polar lows can induce property damage in high-latitude coastal regions and considerably disrupt the oil industry in the Arctic. The impacts of sudden stratospheric warmings (SSWs) on polar lows during 1979-2016 are examined. The tropospheric circulation anomalies are characterized by the negative phase of the NAO following SSWs, and polar low activity decreases significantly over the Labrador Sea, which can be attributed to reduced occurrences of marine cold-air outbreaks (indicated by the difference between the sea surface temperature and 500-hPa air temperature) and surface turbulent fluxes. In contrast, anomalies of polar low track density are largely insignificant over the Nordic Seas. The regionally relationships between SSWs and polar lows are consistent with the regional difference in the link between the NAO and polar lows. Our study suggests that skillful prediction of SSWs may have the potential to improve the extended-range forecast of polar low activity over the Labrador Sea.