Watching the lake water temperature is proving to be very interesting. The water temperature sensor is a few feet below the surface. The lake has been calm recently and the water temperature has settled to a steady 39-40 deg F. Yesterday (Monday) was windy and you see a dip in the blue lake temperature line because mixing occurred which drove some of the cooler water near the surface down to the sensor. I would say if you measured the temperature from the surface down to the sensor on a calm day you would find the temperature profile to look like that shown in the chart below where you would read temperature from the chart from left to right as the lake temperature profile from surface to the probe ending at 4C (39.2F). (image from:http://www.marietta.edu/~mcshaffd/aquatic/sextant/physden.gif)
When the wind mixes the water we begin to see an indication of the surface temperature which is probably near or just under 35 deg F presently. When the wind stopped like today the water again re-statifies: warmer 39F deg water goes to the bottom and water cooler than 39F goes back to the surface.
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