On 10 January, 1998 a massive arctic air outbreak moved across an anomalously warm Lake Michigan. The strong cold and dry westerly winds impinging on the western lake shore produced an exceptionally unstable convective boundary layer that resulted in precipitating convective snow bands on the lee side of the Lake. The Lake-ICE (Lake Induced Convection Experiment) was operating on this day and sent both the Wyoming King Air and NCAR Electra equipped with Edora Doppler to observe the evolving atmospheric structure of the convective boundary layer and the evolution of heat and moisture fluxes across the Lake.
The setup for this case provided an exceptionally ideal laboratory for the evaluation of a numerical simulation of the convective boundary layer. Local model predictions made in real time featured horizontal resolution of 20 km, but provided excellent predictions of the airmass evolution across the lake and the resulting snowfall on the lee side. Subsequent experiments with 10 km resolution revealed important links between the efficiency of convective overturning and large scale forcing resulting from the passage of a vorticity center aloft. Now in a research mode, the model is being run at a resolution of 1 km (locally) in an attempt to explicitly simulate the banding of convective clouds observed during Lake-ICE.
Computer animated results of these simulations will be presented at the conference and compared directly to observations made as part of Lake-ICE. Model diagnostics will be employed to reveal the relevant microphysical and dynamical processes leading to the observed cloud structures. Sensitivity tests will be used to explore the explicit interaction between local cloud processes and large scale forcing.