Polar Low Genesis and Intensification Sensitivities to Oceanic Surface Fluxes Using an Idealized Model

Polar Lows are difficult to predict maritime mesoscale cyclones that develop at high latitudes and have short lifecycles. Their development is often associated with cold air outbreaks and they generally form near a sharp gradient in surface temperature (e.g. air moving from cool continental air toward relatively warmer ocean water). Here we present a study of the polar low genesis and intensification mechanisms using an idealized polar model with the Navy’s Coupled Ocean–Atmosphere Mesoscale Prediction System. Our model resolution is 5 km with a 2000 x 3000 km² domain size centered at 60 N with a meridional land boundary at the center of the domain. In our control simulation, the land temperature is fixed at 258 K and the ocean temperature is fixed at 278 K spatially at all times. We initialize with a westerly (flowing from land to ocean) baroclinic jet with a maximum wind speed of 30 m s^-1 and a surface air temperature equal to the land temperature. Despite the cool sea surface temperatures, strong oceanic surface fluxes still exist and provide heat and moisture to even cooler, dry environmental air. We believe that these surface fluxes are a critical part of not only the polar low generation, but also the diabatic intensification processes. We will discuss the sensitivity of the polar low generation and intensification rates to the i) environmental baroclinicity and stability, ii) initial condition perturbations, and iii) the land-sea temperature difference. These results will provide insights into how polar lows form and intensify, which will ultimately help to improve their prediction.