The Stable Internal Boundary Layer over a Coastal Sea. Part II: Gravity Waves and the Momentum Balance

Abstract Observations of the mean and turbulent structure of the marine atmospheric boundary layer (MABL). obtained using the U.K. Meteorological Research Flight C-130 Hercules aircraft are used to investigate the momentum balance over the Irish Sea when warm air is advected offshore. The marine boundary layer is made up of two layers: a strongly stable internal boundary layer (IBL). and a stable residual layer located between the top of the IBL and the base of the planetary boundary layer inversion. Measurements obtained near the upwind coast indicate that the flow is highly ageostrophic. Downwind of the Irish coast, there is a transition toward equilibrium between the geostrophic, Coriolis. and friction components of the flow along part of the flight track. However, another segment of the flight track indicates an imbalance between the pressure gradient and the other measured terms, which may be attributable to gravity waves affecting the adjustment process. This is more apparent in the leg perpendicula...