Observations of the Influence of Lake Erie on Lake Ontario Lake-effect Snows: OWLeS Case Study

It is well known that atmospheric modification by upwind lakes can enhance the development of lake-effect snow storms over downwind lakes. Striking examples of this can be seen as lake-effect cloud bands extending between the Great Lakes (lake-to-lake, L2L, cloud bands) during fall and winter months. Detailed observations of L2L bands have rarely been taken, however, limiting our ability to evaluate numerical model simulations and answer key questions of processes involved.

This presentation will describe the 28 January 2014 lake-effect snow event, during which air modified by Lake Erie overspread parts of Lake Ontario, potentially influencing lake-effect storm evolution over the latter. Unprecedented observations taken during the Ontario Winter Lake-effect Systems (OWLeS, https://www.eol.ucar.edu/field_projects/owles) field project were analyzed to determine how the lake-effect boundary layer evolved as it flowed from the land area between the lakes, across the southern shoreline of Lake Ontario, and finally over the open waters of that lake.

A mesoscale stationary region of decreased cloudiness and snowfall rates, and lower PBL tops was evident from about 5 km upwind of the Lake Ontario shoreline to about 10 km downwind. Superimposed on this region were intense local downdrafts resulting in local sharp decreases in the depth of the PBL, identifiable by downward penetration of stable above-boundary layer air. Based on Wyoming Cloud Radar observations, these local downdrafts were always present, but not stationary. Implications of these mesoscale and microscale downdrafts on convective growth over Lake Ontario will be discussed.