Land Surface Roughness Effects on Lake Effect Precipitation

Abstract

The land use of the Great Lakes region has changed significantly during historical times, and continues to change. As a preliminary step in investigating the overall effect that this might have on climate, attention is focused here on one forcing factor and one effect—land surface roughness length and lake effect precipitation, respectively—that are anticipated to be particularly sensitive pieces of the land use-climate interaction. On both a monthly basis and in an individual case of lake effect precipitation, a reduction of land surface roughness reduces the total amount of lake effect precipitation. It also reduces the degree to which the precipitation is focused on the area closest to the lakeshore. The largest reductions occur immediately adjacent to the lakeshore in an area smaller than the overall lake effect zone. In the individual lake effect event that is investigated here, precipitation increases in some places farther inland when surface roughness is reduced. Because this increase in precipitation farther inland appears to be associated with significant topography, this result is most valid for lake effect zones where there is a high topographic relief, such as near southeastern Lake Erie (the main focus of this study), and to the south and east of Lake Ontario. This displacement in location of precipitation is particularly crucial where the boundary of the drainage basin is near the shoreline, and can indicate a flux of moisture out of the Great Lakes drainage basin and into another basin.