Internal Boundary Layers and Fog Past Mid-Ocean Islands*

The fog and turbulence interactions in the marine atmosphere (FATIMA) project serves to better understand the role of turbulence in fog formation in marine environments. The land component of the first phase of FATIMA involved field measurements on Sable Island, which is a 40 km long and 1 km wide island located 200 km southeast of Nova Scotia, Canada. Its location in the Atlantic Ocean in the Grand Banks area makes it a suitable place to characterize fog in the marine boundary layer. Nevertheless, due to discontinuities of properties at the land-ocean interface, internal boundary layers (IBLs) develop over and past the island, thus modifying fog. The fluxes and turbulence within these IBLs may be very different compared to the marine boundary layer, thereby complicating the interpretation of measurements over the island. In this study, we aim to quantify the IBL height as a function of the distance from the land/ocean discontinuity and the relevant surface parameters. Using measurements at Sable Island and accompanying high resolution (LES) simulations, we study how the turbulence and fluxes change inside and outside the IBL and asses its influence on the life cycle of fog. In this paper, we will present preliminary findings on the IBL height and turbulence.