Temporal Distributions of Temperature and Moisture Content of a Brazilian Field under Mild Weather Conditions

Heat transfer and moisture movement in porous media are closely related and play a central role in hydrology, atmospheric sciences, geophysics, and environmental physics. In particular, the hydrological and physical characteristics of the media and the atmospheric variables subject to the prevailing climatic conditions are strongly decisive factors. The surface layer of soil is of great influence and an increasingly important focus in this environment is the detailed knowledge of the hydrological and thermal regime, and the factors controlling them. This paper presents the results of measurements of soil volumetric water contents and temperatures at 20, 100, 200, 300 and 400 millimeter depths below the surface of a sparsely vegetated Brazilian field soil, over a period of 60 days and on hourly basis. The pattern of evolution of soil moisture at the topmost layer, especially on sunny days with no precipitation, can be described with a slight water loss generally between the first 6 or 7 hours of the day, followed by a rewetting period which lasted until 11 am after which a drastic water loss was observed. The soil mean volumetric water content +/- standard deviation over the entire period of investigation was 0.27 +/- 7.235, 0.25 +/- 3.499, 0.17 +/- 4.728 and 0.16 +/- 11.732 m(3)m(- 3), while the soil mean temperature +/- standard deviation was 17.8 +/- 2.687, 17.5 +/- 2.046, 17.4 +/- 1.666 and 17.4 +/- 1.248 degrees C, respectively, at depths 20, 100, 200, and 400 millimeters. While the standard deviation in temperature measurements was very high at the topmost layer and decreased with increasing depth, there was no consistent pattern observed with deviations in the measured volumetric water contents due to evaporation and rewetting effects.