Large-Eddy Simulations #37 and #39: Lake-ICE TIBL

LES 39 is simply a continuation of LES 37 with predictive TKE turned on. The first 32-minutes, LES 37, was run without predictive TKE. Turning on the predictive TKE disrupts the apparently "frozen rolls" which form during the first 32 minutes.

PROBLEMS: (1) In this simulation, the air flowing into the domain on the western wall is not turbulent. Yet, we have no observations of laminar air advecting offshore. Instead, we've always observed some type of pre-existing mixed-layer which the lake driven boundary layer grows into. We expect this strongly effects the growth rate of the TIBL and convective structures. (2) "Frozen rolls" develop. Lidar observations usually show cells in the lower ML, and constantly changing patterns elsewhere. (3) The model does not have stochastic backscatter built in. This may effect the solution (see Mason & Thomson, 1992, JFM, 51-78.) (4) Grid-anisotropy approaches 15:1 near the bottom of the model. (5) The wind has been adjusted so that it blows perpendicular to a straight shoreline. Future simulations will address these issues.

ACHIEVEMENTS: The model produces steam-fog, accelerating winds, and a mixed layer that deepens with offshore distance. Non-periodic inflow and outflow boundary conditions are implemented. We ran 6.4 million grid points at 0.25 s time step for about 6 weeks to produce this 1-hour simulation. The mesh size matches the lidar resolution (15 m) and the domain begins to cover scales which could contain several rolls, cells, etc.

LES RUN #37 and #39: Click here to see the NMSTASK file for LES 37.
Click here to see the NMSTASK file for LES 39.
This domain is 6 km (east-west) by 3 km (north-south) wide.

UW Lidar // Feb 18, 1999 //

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