Soil Temperatures - Update

This is an update of a post published on 02-Aug-2013 which describes the hole in the ground used to collect soil temperatures.  I now have just over a little more than one year's data which makes it possible to look for patterns in the data and do a year-on-year comparison.  I started this project in August 2012 just as the ground was starting to cool after the summer.  The full data set is shown below:

The same general patter is present in the Autumn of 2013 as it was in 2012 with the topsoil cooling more quickly than the sub soil.  The maximum values of topsoil temperature were observed in July when there were several weeks of clear sky when the Sun was high in the sky.  The lows were towards then end of long winter when it was April before Earth and Englishman felt warm in the garden.

So far, weather at the end of Autumn has been milder than in 2012 and the subsoil temperatures are two to three degrees higher than last year.  The topsoil more or less follows the air temperature but, it's variation is increased by radiative heating and cooling can lead to loss or moisture and frost respectively.

The observations from the last month illustrate the complexity of the heating and cooling processes.  During the weekend of 13-Oct,  average air temperatures had fallen to below 10 deg. C (cold air from mainland Europe?) and the topsoil temperature fell below that of the subsoil.  A week later, average air temperature rose to more than 15 degrees (warm air from the Atlantic?) and the situation was reversed, the topsoil was warmer than the subsoil.  In addition to air movements (note to self, try and look at a weather map each day and see what's happening), there would also have been radiative cooling and heating.

After a year, the ritual of poking a wire down a hole in the back yard at dusk on Sundays is well established, data on this web page is periodically updated:

Brighton Webs - Soil Temperature