This graph is from in a Scientific American article, which says "The graph is courtesy of J.A. Bolker and D.C. Meredith, University of New Hampshire, and is based on data from Elliott, P.; Cowan, I. M.; and Holling, C. S., 1977. Prey capture by the African lion. Canadian Journal of Zoology 55(11):1811-1828." Two ways of [...]
The data for this graph comes from Lake Superior Meteorological Buoy at the University of Minnesota-Duluth. The data was gathered at 5:00 AM on July 28, 2011. Similar data, along with an interactive graphing view, are available for many other dates back to 2008. The graph was produced with GeoGebra.