TITLE:
Time-Dependent Dirichlet Boundary Conditions for Simulating Seasonal Change in Soil Temperature Profile
AUTHORS:
Ippei Iiyama
KEYWORDS:
Bulk Density, Heat Balance, Heat Capacity, Newton-Raphson Method, Nonlinear Equations, Particle Density, Relative Humidity, Thermal Conductivity, Three Phases, Water Content, Water Potential
JOURNAL NAME:
Journal of Geoscience and Environment Protection,
Vol.14 No.4,
April
10,
2026
ABSTRACT: Soil temperature is a key factor for growth and development of plants, and its regime should be quantified spatially and temporally through numerical simulations with concise boundary conditions. Aiming at evaluating the effectiveness of applying either of the time series of daily-averaged air temperatures and that of daily-averaged soil surface temperature as the surface boundary condition (air-temperature BC and surface-temperature BC), this study numerically simulated seasonal change in soil temperature profile with the time-dependent temperature boundary conditions. The resultant numerical solutions reproduced well the general trends of day-to-day and seasonal changes in measured soil temperatures in both the simulations with the air-temperature BC and that with the surface-temperature BC, while the latter gave the slightly better solution than the former. Based on the concept of thermal time and literature values about thermal time for germination of various herbaceous plants, the numerical solutions also indicated that the sizes of simulation errors can cause the estimation error of less than 1 [d] for predicting the number of dates required for germination under commonly-found situations. Therefore, it was concluded that the time series of air temperatures can become a concise surface boundary condition for predicting or reproducing the seasonal change in soil temperature profile when the temporal resolution of the simulation is set as one day, while the time series of surface temperatures is superior to those of air temperatures as the surface boundary condition.