Surface Waves Generated by Polar Lows: Satellite Observations and Simulations

Results of investigations of surface waves generated by Polar Lows (PLs) in the Barents and Norwegian seas are presented. It is known that the PLs can generate abnormally high waves (up to 10m height) comparable to the waves in tropical cyclones (TCs). Therefore development of methods for prediction and evolution of waves under PLs is extremely important to ensure the maritime and coastal infrastructures safety in the Arctic.This study is based on the synergy of the satellite altimeter measurements of wave heights, and model simulations using a parametric wave model proposed by Kudryavtsev et al., 2021. The input parameters of the model, including atmospheric data and sea ice mask were taken from the reanalysis ERA5 and the database of the University of Bremen, respectively. Three case studies are considered for intense PLs of different type: "spiral"- and "comma"-type. Results of the model simulations are compared with the satellite altimeter measurements. Unlike TCs, wind field in PLs and their trajectory are strongly variable in space and time, and PLs' lifetime is short (from hours to days). However, despite these differences, the group velocity resonance between generating waves and moving wind field (revealed in TCs) can also be fulfilled in PLs. This mechanism leads to appearance of abnormal waves whose heights and wavelengths significantly exceed expected values following from observed wind speed and size of PL. As found, the group velocity resonance in PLs does not appear due to PL translation, but due to movement of the front in PL. Waves of high-energy are generated inside the moving front area of PL and then emitted ahead the front as swell. It is concluded that the PLs of the "comma-type" play a major role in generation of abnormally high waves in the Arctic.