Numerical simulation of boundary layer development and convective structure over Lake Michigan during Lake-ICE

Boundary layer development across Lake Michigan and the structure of convection during a lake-effect snow event on 13 January 1998 are examined with numerical simulations. This case was well documented by the Lake- Induced Convection Experiment (Lake-ICE). The Advanced Regional Prediction Model (ARPS) was used in a multiple-nested grid formulation. Both simulations and observations indicate a shallow boundary layer of less than 400 m depth in the cold air upwind of the lake. The boundary layer grew rapidly upon reaching the relatively warm water over the lake. Precipitating clouds developed over the first 1/3 of the distance across the lake. Simulation results and observations show a non-roll (cell or random) convective structure over the lake, changing to a linear pattern as the cloud passed onshore over western Michigan. Comparisons with observations will include ELDORA radar derived wind fields and convective patterns and in-situ data from the NCAR Electra and University of Wyoming King Air aircraft. Further simulation studies investigate influences of variations in lake surface temperatures and presence of Lake Superior upwind on the development and structure of the convection.