INFLUENCE OF TEMPERATURE VARIATIONS AND THERMAL DIFFUSIVITY ON SOIL HEAT FLUX OVER SOME LOCATION S IN ONDO STATE, NIGERIA.

Abstract

This work looks at the influence of temperature variations and thermal diffusivity on soil heat flux over some locations in Ondo State, South-West Nigeria. Soil properties such as moisture content, bulk density, porosity and soil heat capacity, at each location for depths of 30, 40, and 50 cm were estimated using laboratory measurements obtained from soil samples gotten from each of the experimental locations. The hourly and mean diurnal temperature distribution along with the values of the estimated soil properties obtained were used in determining the thermal diffusivity of the soil, and this was used alongside the average of the daily temperature values to estimate the soil heat flux using the phase-lag method and the Fourier one dimensional heat conduction equation respectively. The set of values of these thermal properties of soil were estimated for both dry and wet season at each location. Results obtained reveal that thermal diffusivity and soil heat flux for the different locations showed increased values during the wet season as compared with the dry season. Soil temperature variations for the dry months were relatively higher at the soil surface but steadily decreased as thermal wave penetrates the soil. From the results, soil heat fluxes were largely influenced by temperature gradients as well as the variations of thermal diffusivity through the soil. The higher the value of thermal diffusivity alongside temperature variations, the more the soil heat fluxes in the positive or negative direction. Also a positive temperature gradient gave a negative heat flux (flow of heat upwards), while a negative temperature gradient gave a positive heat flux (flow of heat downwards in the soil).