Numerical experiments on a possible mechanism of cyclogenesis in the Antarctic region

Polar lows are observed to form in the circum-Antarctic ocean, where strong meridional thermal contrast in the atmosphere is normally associated with large heat fluxes from the sea. In the present study, using a two-dimensional non-hydrostatic model, we examine the growing stage of disturbances that bear many characteristics in common with observed polar lows, as, for example, warm mesoscale updrafts where the latent heat is released. We show here that such growing disturbances do not depend, for their structure and scale, on the initial condition chosen. Growth rates are considerably larger than those of modes in the absence of surface heat fluxes, and may be sustained for several days.