Daily, seasonal, and annual relationships between air and subsurface temperatures, Smerdon, J. E.; Pollack, H. N.; Cermak, V.; Enz, J. W.; Kresl, M.; Safanda, J.; Wehmiller, J. F. , Journal of Geophysical Research-Atmospheres, Apr 4, Volume 111, Issue D7, p.-, (2006), Doi 10.1029/2004jd005578 Abstract