Idealized Model Simulations of Lake-Induced Mesoscale Vortices

Convective boundary-layer processes are known to influence mesoscale circulations under a variety of conditions. For example, lake-induced vortices are one of several types of mesoscale circulations that occur in the Great Lakes region during Arctic cold-air outbreaks when relatively large sensible and latent heat fluxes are present. On two occasions during the Lake-Induced Convection Experiment (i.e., Lake-ICE) mesoscale vortices were observed. The atmospheric conditions during these events were similar to the general conditions that have been reported from previous events. However, conditions cited by previous studies as favorable for vortex development are very qualitative and have been only briefly discussed in the scientific literature. These conditions include: 1) low surface wind speeds 2) large lake-air temperature differences and 3) low atmospheric stability. A series of idealized simulations were conducted using a hydrostatic, three-dimensional, primitive equation model with 17 vertical levels. A single circular lake and flat terrain were used during each experiment to reduce the complicating influences that multiple lake interactions and differences in ambient flow direction with respect to lake orientation can provide. We will present results from our idealized model simulations that determined the sensitivity of lake-induced vortex development to lake-air temperature differences, atmospheric stability, and ambient wind speed. The simulations will be used to quantify the influence of these conditions on the vortex intensity and three-dimensional thermodynamic and kinematic structure. The range and combination of conditions for vortex development will be presented and compared to atmospheric conditions during the Lake-ICE vortex cases and previously observed events.