Abstract
For soil moisture sensing, a thermal inertia model based on the heat balance and one-dimensional heat transfer of the earth's surface was constructed analytically by applying some basic relationships between the daily range of surface temperature and the heat balance terms formulated by Laiktman and Uchijima, and the solution of heat transfer derived by Ohga. This model was enlarged for airborne and satellite remote sensing of soil moisture. The procedure was verified using heat balance data obtained at a ground truth center in the Kujukuri plain.
In the heat transfer theory, the concept of thermal inertia explaining the heat conductance inherent to each material is well known. This thermal inertia model has been developed for soil moisture sensing from evaluation of previous thermal inertia models, and is more advantageous than other models because of its simplicity, the validity of its physical/mathematical solution and its incorporation of surface relative humidity in appropriate heat balance terms.
It is also practical, since it allows the use of two datasets from remote sensing twice a day. The daily range estimated from measurements made in the early morning and at noon can eliminate the noise of measurement error for the larger dynamic range of measurement values. From this evaluation of thermal inertia it was clarified that soil moisture remote sensing and its procedure based on heat balance and thermal inertia derived from physical and mathematical solutions is more accurate than that based on apparent thermal inertia, and results of simulation and iteration. Although some problems still remain with this procedure, it can be used as a basis for remote sensing of soil moisture.
