Numerical simulations of a cold-season turbulence outbreak

The 9-10 March 2006 case, where a significant outbreak of flight-level turbulence was documented (Knox et al. 2008, J. Atmos. Sci.), has been simulated using cloud-resolving model over a subcontinental scale domain. The model accurately simulates two regions of convection including 1) a line of deep convection ahead of the synoptic cold front and upper-level trough and 2) a zone of shallower convection farther west near the center of the upper level trough. In both regions, the convection extends up to the tropopause, which is located at 12 km MSL in the eastern band and at only 8 km MSL farther west. The reported turbulence is situated well above the simulated tropopause and extends horizontally from several km above the westernmost region of convection near the border of central Missouri and Illinois northward to the northern edge of the precipitation shield near the Wisconsin-Illinois border. Using this simulation and related model sensitivity studies, both adiabatic and convection induced turbulence mechanisms are being investigated as possible causes for the reported turbulence.