## 2 Data and Analysis Methods  
### Satellite Measurements  
The PLs were identified from the cloud signatures on the IR images of the spectro-radiometers MODIS onboard the Aqua and Terra satellites, VIIRS onboard the Suomi NPP satellite, and AHVRR onboard the NOAA series and MetOp-A/B satellites. The sensors record the Earth's radiation in the thermal spectral range of 10.2-12.4 \(\mu\)m, which characterizes the temperature of the underlying surface and representing the cloud top temperature in the presence of clouds. Using IR images from seven satellites allowed for observing the PLs centers and cloud structures with a time discreteness of approximately 70 min with a spatial resolution of 375 m (VIIRS) and 1000 m (MODIS and AVHRR). The PL tracks obtained from the IR images served as verification. From a series of IR images of cyclonic cloud vortex, we estimated the location, duration and size of PLs from genesis to decay. PL genesis (dissipation) corresponds to the first (last) image with a clearly formed cloud vortex. PL size is defined during its mature phase by the minimal diameter of a circle that encompasses the cloud vortex. The criterion of 15 m/s was selected as the lower threshold of the near sea surface wind speed in the PL [22]. Several atmospheric parameters were derived from the measurements of the Advanced Microwave Scanning Radiometer (AMSR2) onboard the GCOM-W1 satellite. In particular, we used measurements of the brightness temperature at 89 GHz frequency in the horizontal polarization--Tb(89H). In addition, we retrieved the near-surface wind speed (W), atmospheric total water vapor content (V) and total cloud liquid water content (Q) using algorithms based on physical modeling of the brightness temperature of the ocean-atmosphere system outgoing radiation [23; 24; 25; 26]. We apply a lower frequency (LF) wind speed retrieval algorithm that uses four brightness temperatures at following AMSR2 channels: 6.9 and 10.65 GHz, horizontal and vertical polarizations. Comparison of AMSR2 wind speed and in situ measurements from eight platform automatic weather stations in the North and Norwegian Seas showed a high correlation (0.9) with the root-mean-square error of 1.6 m/s [27]. We used the brightness temperature from the AMSR2 Level 1R data. The footprint resolution varies from 35 km \(\times\) 61 km on 6.925 GHz to 3 km \(\times\) 5 km on 89.0 GHz. The sampling interval is 10 km \(\times\) 10 km for all bands except two channels at 89 GHz, for which it is 5 km \(\times\) 5 km. For a more reliable analysis of the wind fields, we masked an area at a distance of about 50 km from the ice edge (the trace resolution used in the algorithm for the lowest frequency of 6.9 GHz). We also used surface wind speed estimates derived from the measurements of the Advanced Scatterometer (ASCAT) onboard the MetOp-A/B satellites with a spatial resolution of 12.5 km and the polarimetric microwave radiometer WindSat onboard the Coriolis satellite [28] mapped to a 0.25-degree grid. These datasets, combined with the AMSR2 measurements, provided 11 wind speed fields per day, enabling PL detection and analysis of their intensity and evolution. The satellite observations were filtered for rain, as precipitation degrades the quality of both radiometer and scatterometer wind speeds. However, in PLs, most precipitation falls as snow due to the extremely cold environment. Moreover, satellite-based total cloud liquid water content in the study area showed values less than 0.3 kg/m\({}^{2}\). Such atmospheric conditions result in reliable satellite wind retrievals [29]. The mean and extreme (95 th percentile) wind speeds within the 300 km radius of the PL center were calculated to compare satellite and reanalyzes representations of the PL development. Note that the coastal and near ice edge zones of 50 km wide were excluded from the analysis because of technical limitations of the sensors. It is known that there is significant uncertainty and inconsistency of high wind speed (above 15 m/s) estimates in different satellite products.