Mesoscale variations in surface heat fluxes over Lake Erie pack ice

Spatial variations in surface heat fluxes can play important roles in the evolution of mesoscale boundary layer variability and convective precipitation systems. For example, variations in lake surface temperature and pack-ice cover have been shown to influence cold-season lake-effect snow system (LES) evolution. The University of Wyoming King Air was utilized during the Great Lakes Ice Cover – Atmospheric Flux (GLICAF) experiment to examine pack ice – heat flux relationships. A recent analysis of one GLICAF case indicated turbulent sensible heat fluxes decreased nonlinearly with increases in underlying lake-surface ice concentration, with the largest decreases corresponding to ice cover concentrations over 70%. Latent heat fluxes were not as strongly correlated, and decreased more linearly, with increasing ice cover. Pack ice distributions upwind of the flux observations influenced mesoscale variations in low-level atmospheric conditions (e.g., air temperatures and moisture contents) which, in turn, also influenced heat flux patterns.

For three days with observed positive heat fluxes from the lake during GLICAF, variations in large-scale atmospheric circulations gave rise to different atmospheric responses to the Lake Erie pack ice. This presentation will examine all three positive heat flux cases during GLICAF to better determine the relative roles of ice concentration and mesoscale atmospheric conditions on heat fluxes. Numerical model simulations of atmospheric responses to surface variations, implications for mid-latitude regional climate and short-term LES predictions will be discussed.