The presence of ground surface snow cover is a regime change for heat fluxes within the near surface soil. The featured chart attempts to illustrate this by looking at air temperature and two inch depth soil temperatures during two recent two day periods using data from the ISU Soil Moisture station near Ames at the 'Kitchen Farm'. These two periods featured a similar downward trend in air temperature, but the first during the 19-20 January period was free of snow cover and February period saw the accumulation of around four inches of snow on 12 February. The main panel plots air temperature vs soil temperature for each two day period. The start of the period is flagged with a star and the end with a circle. The inset plots are more conventional time series of these two variables. The main panel is attempting to show the regime change as you can see much different behavior between the two periods. These two periods start off with nearly identical values of air and soil temperature, but their behavior as air temperatures cool is quite different. Snow acts to trap soil heat from escaping to the atmosphere and also helps to buffer the effects of much colder air near the ground surface.

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Tags:   snowcover   soil