Coupled water and heat flow in a grass field with aggregated Andisol during soil-freezing periods

摘要: Abstract During soil-freezing periods, coupled water and heat flow is important for predicting frost depth unsaturated between frozen unfrozen soil. We investigated in Andisol with aggregated soil structure at a grass field during periods. The retention curve (WRC) had stepwise shape, which content, θ , decreased drastically air entry value, h  = −0.3 m, matric potential,  = −10 m. profiles of temperature, T an were measured using thermally-insulated tensiometers thermo-time domain reflectometry (thermo-TDR) probes the northeastern part Japan. As surface froze, moved upward because potential gradients. Although water-saturated may be described generalized Clausius–Clapeyron theory, theory cannot express When started to freeze conditions field, significant factor determine temperature freezing point depression water. proposed modified relate both saturated conditions. model showed good agreement calculated experimental – relationship. Sensible flux due small gradients transition layer layers. However, when front advanced further below surface, latent appeared larger than sensible phase changed ice. transport should taken into account better prediction Andisol.