Average Diurnal Wind Variation in Southwestern Lower Michigan

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  • 1 Department of Atmospheric and Oceanic Science, University of Michigan, Ann Arbor 48109
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Abstract

Three years (1974–76) of wind data for stations 1.5, 20 and 55 km from the eastern shore of Lake Michigan are analyzed to determine effects of the lake on seasonal and annual distributions of wind speed and direction. The results are interpreted in terms of both specific lake breeze effects and lake effects in general.

Specific lake breeze effects are most evident at the station 1.5 km from the lake. They include a faster rate of increase of average wind speed in the morning and more circular hodographs than at the stations further inland. At the station 20 km inland, lake breeze effects are more subtle. A change in the rate of increase of wind speed, associated with the passage of the lake breeze, is evident in the summer season but not on an annual basis. Lake breeze effects that are evident there on an annual basis include a high frequency of occurrence of variable wind directions and wind directions which differ by 90° or more from those at the shoreline station. In addition, the summer and annual hodographs are slightly more circular than those for the station 55 km inland. That station shows no evidence of lake breezes or their effects.

General lake effects are evident at all three stations both in summer and on an annual basis. The hodographs for these stations, as well as for a station more than 175 km inland, have orientations and shapes that indicate significant diurnal response to the east–west (across-shore) wind component, not evident at stations upwind of the lake.

Abstract

Three years (1974–76) of wind data for stations 1.5, 20 and 55 km from the eastern shore of Lake Michigan are analyzed to determine effects of the lake on seasonal and annual distributions of wind speed and direction. The results are interpreted in terms of both specific lake breeze effects and lake effects in general.

Specific lake breeze effects are most evident at the station 1.5 km from the lake. They include a faster rate of increase of average wind speed in the morning and more circular hodographs than at the stations further inland. At the station 20 km inland, lake breeze effects are more subtle. A change in the rate of increase of wind speed, associated with the passage of the lake breeze, is evident in the summer season but not on an annual basis. Lake breeze effects that are evident there on an annual basis include a high frequency of occurrence of variable wind directions and wind directions which differ by 90° or more from those at the shoreline station. In addition, the summer and annual hodographs are slightly more circular than those for the station 55 km inland. That station shows no evidence of lake breezes or their effects.

General lake effects are evident at all three stations both in summer and on an annual basis. The hodographs for these stations, as well as for a station more than 175 km inland, have orientations and shapes that indicate significant diurnal response to the east–west (across-shore) wind component, not evident at stations upwind of the lake.

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