Inside Katabatic Winds Over the Terra Nova Bay Polynya: 2. Dynamic and Thermodynamic Analyses

Abstract

AbstractSurface fluxes and atmospheric boundary layer budgets of enthalpy and momentum are quantified using bulk and integral methods based on measurements obtained during a research vessel transect across the Terra Nova Bay polynya during an intense late autumnal katabatic wind event. The surface sensible, latent, and net radiation heat fluxes had maximum upward values of 2,500 ± 600, 400 ± 100, and 100 ± 7 Wm−2, respectively, which occurred over open regions that had been cleared of sea ice by the wind stress. In these open areas, sea spray enhanced the sensible and latent heat fluxes (LHFs) by an estimated 106% and 18%, respectively. As sea ice formed on the surface and became thicker in the downwind direction, the sensible and LHFs decreased to 50% of their maximum values over pancake ice and to 5% at the downwind end of the transect, where snow‐covered young ice flows were present. Snow growth removed over 50% of the water vapor that came from the surface. The surface wind stress ranged from mean values of 2.9 Nm−2 in the most upwind regions to 0.9 Nm−2 at the end of the transect, with smaller scale variations of almost a factor of three due to different surface types (roughnesses) and gustiness. The downwind slowing and turning of the wind vector can be almost entirely explained by frictional and inertial forces, indicating the horizontal pressure gradient was weak. This case could serve as a case study for future modeling studies of coastal polynyas.