Daily Changes of Temperature Near the Ground

The climate of the air near the ground is regulated by the same processes as the climate in the atmosphere. However, bigger extremes occur due to the exchange of energy and are modified by the type of soil and the vegetation (Fig 2.1.5). This is shown clearly by the course of temperatures during one day (Walter 1960; Gates 1965). We shall first consider an area without vegetation, vertical to the incoming radiation source, and then modifications resulting from different inclinations, exposure and, most of all, vegetation cover.


The long-wave radiation balance with high outgoing radiation and low incoming radiation substantially cools the earth's surface; the negative radiation balance is partially compensated by heat conduction from the soil, and by the low heat exchange (convection) with the air layers near the soil surface. Formation of dew and hoar frost may compensate this effect due to heat released in condensation and freezing. On a cloud-free night, temperatures may fall more than 10 K below the temperature of the atmo-

narrower because of the increase in natural as well as anthropogenic trace gases, especially chlorofluorocarbons, ozone, methane, nitrogen dioxide and C02. The earth's temperature rose due to a release of trace gases between the Palaeozonic and Eozene periods.

• The temperature of the earth results from a balance between the energy flows. It is difficult to predict the temperature and climate, as the slightest imbalance in opposing heat flows has considerable effects on the temperature, as long wavelength radiation emission is proportional to the fourth power of the temperature (Stefan-Boltzman law).

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