Lake Michigan’s waves in winter vs summer

 Dear Tom,
I do quite a bit of boating on Lake Michigan, and I have noticed that the waves are higher in the winter than the summer. Why is that?
Ted Ackron, Waukegan
Dear Ted,
The explanation is in the air/water temperature differences between winter and summer. Cold air over warm water (the winter situation) transfers more wind energy to the water and builds higher wave than does warm air over cold water (the summer situation).
When cold air blows over warmer water, it heats, lifts off the water surface and is replaced by higher-velocity wind from above. Stronger winds are constantly sinking to the lake surface. In summer, the opposite happens. Warm air blowing over colder water is chilled, becomes stable, hugs the lake surface and slows because of friction. Stronger winds higher up do not build down to the lake surface.

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