The inconvenience of this formula is its dependence of the annual amplitude of the soil’s surface temperature,
and its diffusivity. Data of annual amplitude of the ground surface are not usually available, and the question of the
effective diffusivity of the ground is complex. Without these data this formula cannot be employed. On the basis of
experimental study undertaken in several climatic areas, Givoni recapitulated his results in a simplified method 3. It
makes it possible to estimate the soil’s temperature according to the weather data of the site, the range damping
factor F and the time lag L defined by the formula: