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What is the current ground temperature, and how much does it vary from week to week? Seems like it would be a slow change in either direction, but I thought I'd ask the pros...Thanks!

Posted February 19, 2007

MIKE MOSS SAYS:      Jo,   As I wrote this, a check of soil temperatures around the region shows mainly values in the 32-36 degree range. These are typically measured at about 4 inches below the surface. This is deep enough to respond fairly slowly to changes in air temperature and to cooling and heating by way of radiative heat loss or gain at the surface. As you might expect, the soil responds more rapidly and with less time lag near the surface, and the the response to heating and cooling above becomes more muted in amplitude and has a longer time lag the deeper you go. Although there is some variability about this, for example, the highest/lowest soil temperatures on a typical day will often occur about 1.5 to 3 hours following the high and low air temperatures. As for week to week variation, around 2-5 degrees change is a typical range, although there can be periods where the temps do not change that much, and other times when the rate is somewhat higher, all depending on how strongly air temperatures are changing, and what cloud and precipitation patterns may be affecting the ground.

You can get a detailed look at hourly soil temperatures for the past 7 days, or, for example, the low and high daily soil temperatures (and time of occurrence)  for the past 180 days, at the the State Climate Office CRONOS data page. See

http://www.nc-climate.ncsu.edu/cronos/map/

Here, click the "info" button above the map, then click one of the green dots, which represent stations that usually have soil temperature data. You can then select hourly, daily or monthly data and the period of time you're interested in, along with which particular measurements you'd like to retrieve.
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