Soil temperature
At many weather stations of the meteorological services, the ground temperature is measured in addition to the air temperature - usually just below the surface of the earth and at a depth of about 20 cm.
The daily variation of the floor temperature is significantly lower compared to that of the air - the lower the lower the measurement. The cause of this uniformity is, on the one hand, the high specific heat of the soil and, on the other hand, the lower night-time cooling .
In the course of the season, not only a decrease in temperature fluctuations can be observed with the soil depth, but also an increasing lagging behind the temperature curve compared to that at the earth's surface ( phase shift ). At a certain depth (typically 6–12 m, depending on the nature of the soil and in particular the water content), the time lag reaches six months, so that here the qualitative temperature curve is exactly the opposite of that on the earth's surface (application: ice cellar ). However, the absolute fluctuation amplitudes at this depth are only small.
With increasing depth of the ground, the influence of the heat radiation from above fades into the background compared to that of the geothermal energy rising from the earth's interior .
As a parameter, the soil temperature is also important for agriculture , fruit growing, botany (thermal tree line ) and zoology ( soil organisms ), as well as for construction ( depth of frost , soil structure) and for the productivity of springs . For example, landslides can be triggered not only by heavy rainfall, but also by melting ground ice . However, this is mainly relevant near the permafrost area , where the glaciation extends down to deeper soil layers. Such effects have also been demonstrated on Mars in recent years.
The annual mean values measured at depths of 6 and 12 m show an increase in soil temperatures in Germany since the mid-1980s. Corresponding to the mean air temperatures, the rise in temperatures in the higher soil layers seems to have started earlier.
Individual evidence
- ↑ Soil temperature ( Memento from February 16, 2010 in the Internet Archive )
- ↑ Climate time series - soil temperature , Potsdam Institute for Climate Impact Assessment
Web links
- Influence of temperature and radiation on the soil temperature, with clear diagrams
- Heat balance of the soil