Mesoscale Boundary Layer Structures Observed During the Lake-Induced Convection Experiment (Lake-ICE)

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The state of knowledge of air-sea interactions indicate that current scientific problems (such as weather forecasting and global change) require increased understanding of marine boundary layers in complex surface and synoptic conditions. Lake-effect snow storms, which develop over the Great Lakes during fall and winter cold air outbreaks, are useful "laboratories" for the study of complex boundary layer growth and mesoscale circulation patterns. Data collected during the recent Lake-Induced Convection Experiment (Lake-ICE) offer a unique opportunity to gain insight into the development of convective boundary layers, mesoscale circulations in complex conditions, and interrelationships between growing boundary layers and the ambient synoptic conditions.Past research efforts of the principal investigators have provided considerable insight into the development of lake-effect boundary roll convection and mesoscale snowbands in conditions of intense surface heating and strongly stable upwind conditions. However, these efforts revealed the importance of atmospheric and surface conditions close to the upwind shore of Lake Michigan, where no observational data were available. Data from Lake-ICE allow for direct testing of these hypotheses and an expansion of knowledge of the effects of non-classic, complex surface and atmospheric conditions on boundary layer growth and mesoscale circulation patterns. Specifically, the principal investigators propose to (1) understand the evolution of roll/cellular convection and boundary layer growth across Lake Michigan, (2) determine the influences of synoptic conditions, lake-surface temperature variations, and air-mass modification by Lake Superior, on boundary layer growth and mesoscale circulations over Lake Michigan, and (3) determine the respective mechanisms controlling the evolution of lake-effect vortices of different scales over the Great Lakes.The proposed research will utilize the unique dataset available from the 1997/1998 field operations of the Lake-ICE, supplemented with data taken during two past field experiments conducted over the Great Lakes. Of particular importance to the proposed research efforts will be the use of the NCAR Electra Doppler Radar (ELDORA), WSR-88D, and satellite observations to quantify spatial and temporal variations in mesoscale boundary layer circulation patterns in lake-effect events. Numerical modeling efforts will use the Advanced Regional Prediction System (ARPS) to develop a better understanding of the physical processes responsible for variations in mesoscale circulation patterns and boundary layer growth in complex convective boundary layers and to determine the sensitivity of their characteristics over a wider range of atmospheric conditions than can be obtained by observations alone. 2