Wind Velocity Measurements on Two Small Ice-Covered Lakes:

This report gives a compilation of wind velocity measurements on Round Lake and Lake Harriet taken over the ice in 2004 and 2005. Results, primarily from the 2004 Round Lake study, are presented and discussed to characterize the wind sheltering effect of tree canopies on lakes. Wind forcing is important for predicting many physical, chemical and biological lake processes, and there is a lack of understanding of the spatial and temporal variation of wind speeds over lakes especially those sheltered by canopies. The objective of this study was to evaluate, with observations, the spatial evolution of an internal wind boundary layer as it flows from a rough canopy of trees and shoreline reeds onto an ice cover of a lake. More specifically, the study sought to determine the streamwise profile of the shear stress on a lake surface, and to establish a relationship between surface shear stress and fetch. The data show that reduced wind shear stress extends across approximately half the diameter of Round Lake (~ 500 m).