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Animation: LES simulations showing ship track sensitivity to background aerosol

This video depicts the albedo field from two LES simulations of a ship track. In the upper panel, the background cloud condensation nuclei concentration is approximately 10-15 /cm3, while in the lower panel, it is 100-150 /cm3. The ship track aerosol perturbation applied to the high background aerosol case is 10x as large as the low background aerosol case in order to make a visible signature, as the weaker perturbation used in the low aerosol case has a much weaker impact under conditions of high background aerosol.

Animation courtesy of Andy Berner

Animation: modeled ship tracks

This video depicts the albedo field from two large eddy simulations (LES) of a ship track. In both cases, background aerosol concentration is 10-15 /cm3. Because the boundary layer in the case modeled is quite shallow (300m) and strongly sheared (wind speed of 20 m/s in downdrafts and 15 m/s in updrafts due to surface drag), the boundary layer organizes into roll cells. This organization results in highly anisotropic bulk turbulent diffusivity of scalars. This can be appreciated by inserting a ship track perturbation aligned with or perpendicular to the roll circulation, and noting that the cloud response is quite different, reflecting the more rapid lateral diffusion of the cloud condensation nuclei when the track is inserted perpendicular to the rolls.

Animation courtesy of Andy Berner