Presenter: Peter Sullivan (National Center for Atmospheric Science)

Description:
The upper ocean is a busy place abundant with vortices, density filaments and fronts spanning horizontal scales in the range 0.1 to 10 km, \ie the so-called ocean submesoscale regime.  The possible  impact of submesoscale ocean variability on the overlying atmospheric boundary layer is however poorly understood.  To investigate possible mechanical and thermodynamical impacts of a heterogeneous ocean surface on the ABL we have carried out process studies using large eddy simulations with nearly 10^10 gridpoints with varying lower boundary conditions. In one family of simulations ABL dynamics are investigated in the presence of single-sided sea surface temperature (SST) fronts with varying temperature jumps and widths.  We find the response of the ABL to heterogeneous SST is dependent on the orientation of the surface winds with the SST isotherms, \ie the ABL dynamics vary with across-front and alongfront geostrophic winds.  These simulations utilize a newly implemented ``Fourier fringe" to overcome horizontal periodicity constraints.  A second family of simulations couples a circular ocean eddy to the surface momentum and temperature fluxes in the LES. As expected ocean currents generate heterogeneity in momentum fluxes but surprisingly also generate swaths of heterogeneity in the surface temperature fluxes. As a result ocean currents can indirectly induce secondary circulations that impact the full ABL.