Modelling daily and annual cycles of temperature in two types of soil

Abstract

Soil temperature influences strongly crop development and growth. The daily and annual periodic variations of soil temperature follow closely the time-course of solar irradiance. The temperature profiles of a Luvisol and a Vertisol, in the mediterranean reagion of southern Portugal, were measured at six depths (2 to 32 cm), and the analysis of daily and annual temperature cycles was performed by means of Fourier series; daily cycles were studies based on data from four typical clear days through the year. Daily course of soil temperature was well described by the two first Fourier harmonics, while the annual course of soil temperature was described satisfactorily by the firs harmonic alone, which explain more than 90% of total variance. Soi heterogeneity effects on the simulation and on wave damping are also discussed.