CGD Seminar - Sullivan

Boundary-layer induced frontogenesis in the ocean surface layer

Peter Sullivan, NCAR/MMM

The spatial and temporal state of the upper ocean boundary layer is determined by a set of complex interactions between submesoscale and small-scale boundary-layer turbulence. Of particular interest here is the life-cycle of a cold dense filament undergoing frontogenesis in the presence of wind and wave generated turbulence. Cold filaments generate secondary circulations in the boundary layer that are frontogenetic with super-exponential sharpening of the cross-filament buoyancy and horizontal velocity gradients.  Within less than a day, the frontogenesis is arrested at a very small width, < 100 m, primarily by a barotropic instability associated with anisotropic turbulence and cross-front horizontal shear. The barotropic instability grows in scale and decays slowly over many hours.  This phenomenon is examined in Large-Eddy Simulations (LESs) with resolved turbulent motions in large-horizontal domains using 10^9 gridpoints. Winds and waves are oriented in directions both perpendicular and parallel to the cold filaments in the LES. The LES solutions show that the boundary layer turbulence is strikingly inhomogeneous in relation to the submesoscale filamentary currents and density stratification.  The spatial and temporal evolution of frontogenesis is dependent on the orientation of the winds and waves.

Tuesday, January 24

Mesa Lab Main Seminar room

11 AM  Refreshments at 10:45

Building:

Room Number: 
Main Seminar room

Type of event:

Will this event be webcast to the public by NCAR|UCAR?: 
Yes - ML-Main Seminar Room - http://ucarconnect.ucar.edu/live
Announcement Timing: 
January 16, 2017 to January 24, 2017
Calendar Timing: 
Tuesday, January 24, 2017 -
11:00am to 12:00pm