Purpose. The aim of the paper is to study the polar low on January 18-20, 2017 using the sensitivity numerical experiments. The experiments were performed to analyse direct effect of the surface energy fluxes and condensational heating on the cyclone structure and intensity.
Methods and Results. The Polar WRF model was used for the cyclone simulations. In order to study the cyclone direct response to the changes in the model, all the experiments started only after the polar low had reached its mature stage at 00:00 on January, 20. Five numerical experiments were performed, in which the following parameters were turned off: 1) sensible heat flux only, 2) latent heat flux only, 3) both surface energy fluxes, 4) phase change heat transfer in the atmosphere and 5) phase change heat transfer in the atmosphere as well as surface energy fluxes. The cyclone intensity was defined by the minimum sea level pressure in its center.
Conclusions. It is shown that in all the numerical experiments, the cyclone intensity as well as its maximum wind speed at the model lowest level decreased. In experiments 1 and 2, the intensity decrease was nearly the same, i.e. at the mature stage, the sensible and latent heat fluxes were equally important for the cyclone intensity. In experiments 1, 3 and 5 (with the sensible heat flux turned off), the atmosphere static stability increased significantly due to considerable decrease of the air temperature at the model lowest level. In experiment 4, the planetary boundary layer became more unstable since evaporative cooling was turned off in the model. In experiments 1, 3 and 5, integral kinetic energy of the cyclone increased despite the fact that its intensity and maximum surface wind speed decreased. It is shown that such a response of the cyclone was, most probably, caused by decrease of the energy dissipation in the surface layer due to the increased atmospheric stability.