Mechanisms of the polar low development

Abstract

<p>In the recent researches, the disagreement on the issue of the mechanisms of the polar low development is observed. Thus, in [1], on the basis of numerical experiments, the dominant role of baroclinic instability during the development of polar low at the initial stage of atmospheric vortex formation is noted, but then the polar low was maintained due to the sensible heat flux from the surface. At the same time, in [2], the dominant role of condensational heating was noted with a minor role of sensible and latent heat fluxes on the ocean surface. It was shown in [3] that sensible and latent heat fluxes between the ocean and the atmosphere play a decisive role both at the stage of baroclinic intensification of the polar low and at the stage of its maintenance; later experiments [4] showed that an increase in the ocean surface temperature leads to the emergence of more prolonged and long-lived polar lows. In this work, the simulations to elucidate the mechanisms of the development of polar low were carried out within the framework of the WRF atmosphere model. As a control experiment, an experiment with certain physical processes available in WRF was used. To assess the sensitivity of a polar low to convective processes in the model, calculations were carried out that were completely identical to the control experiment, but with the shutdown of certain physical processes. When the heat generated by condensation was turned off, the role of latent heat was studied. This was done by turning off the contribution of heat to the temperature profile in the module responsible for the microphysics of clouds. To assess the sensitivity to heat fluxes on the surface, a numerical experiment was carried out with such switching off. To reveal the role of the baroclinic growth as a mechanism for intensifying the atmospheric vortex, both heat fluxes on the surface and the release of latent heat during condensation were turned off. The role of energy fluxes on the ocean surface during the development of the polar low was demonstrated, which forms new directions for the study of this issue.</p><p>This work was supported by a RSF grant № 21-77-00076.</p><p>References</p><ul><li><em> </em>Føre, I., Kristjánsson, J. E., Kolstad, E. W., Bracegirdle, T. J., Saetra, Ø. and Røsting, B. (2012), A ‘hurricane-like’ polar low fuelled by sensible heat flux: high-resolution numerical simulations. Q.J.R. Meteorol. Soc., 138: 1308–1324. doi:10.1002/qj.1876</li> <li>Watanabe, S.I. and H. Niino, 2014: Genesis and Development Mechanisms of a Polar Mesocyclone over the Japan Sea. Mon. Wea. Rev., 142, 2248–2270, https://doi.org/10.1175/MWR-D-13-00226.1</li> <li><em> </em>Kolstad, E. W., T. J. Bracegirdle, and M. Zahn (2016), Re-examining the roles of surface heat flux and latent heat release in a “hurricane-like” polar low over the Barents Sea, J. Geophys. Res. Atmos., 121, 7853–7867, doi:10.1002/2015JD024633</li> <li>Kolstad, E. W. and Bracegirdle, T. J. (2017), Sensitivity of an apparently hurricane-like polar low to sea-surface temperature. Q.J.R. Meteorol. Soc, 143: 966–973. doi:10.1002/qj.2980</li> </ul>