航空機実験によるサーマルイナーシャにもとづく九十九里平野の土壌水分推定

抄録

A thermal inertia model based on the heat balance and one dimensional heat transfer of the earth's surface for the remote sensing was established by the analytic and mathematical solution techniques. The thermal inertia model for determining soil moisture was applied to airborne multispectral scanner (MSS) data to produce soil moisture map in the Kujukuri coastal plain.
Our mapping procedure consists of the formulating the equation, the discriminant analysis of land cover by sample data from field observation and MSS data, and computer mapping technique.
The equation for determining soil moisture was developed incorporating airborne MSS data and heat balance terms obtained at the micro-meteorological observation field at a time. One of these terms is the relative humidity of the soil surface. This parameter cannot be estimated by the remote sensing data itself because of unknown parameters in the estimate equation based on heat balance. Therefore, it was derived from the normalization of albedo based on the empirical model using the data obtained from the MSS measurement, the micro-meteorological measurements of the observation field of National Institute for Environmental Studies (NIES) and in the Kujukuri coastal plain. The other parameters were substituted by the heat balance terms such as diffusion velocity (coefficient), downward longwave radiation, global solar radiation at the observation field of micrometeorology.
Thus obtined, our model for soil moisture enabled estimate of the soil moisture of bare soil and sparsely vegetated surface. The result of the experiment seems rather good. However, some parameters such as diffusion coefficeint, downward longwave radiation, ratio of vegetation cover in the model has to be examined in further analyses. Also, the model's application to the hilly country needs the information of the inclination of the ground surface and its processing system in this procedure.