Limited polar low sensitivity to sea-surface temperature

The sensitivity of the intensity of polar lows to changes in the sea-surface temperature (SST) is investigated. This is done by using an axisymmetric non-hydrostatic numerical model. It is found that the intensity of the simulated polar lows responds linearly to SST perturbations, with positive perturbations leading to deeper sea-level pressure (SLP) depressions and higher azimuthal winds. The numerical simulations give an SLP depression sensitivity of only about −0.6 hPa K−1 and a sensitivity of the maximum azimuthal wind of only about +0.6 m s−1 K−1. This is about one order of magnitude less than the sensitivity of the theoretical maximum intensity. It is suggested that the very limited sensitivity can be explained within the wind-induced surface heat exchange (WISHE) theory. The limited sensitivity can thus be attributed, in roughly equal parts, to the limited efficiency with which the polar low extracts heat from the ocean and the limited mean height of the convection.