Development Argolithms for Hydrological Information by Using Systhetic Aperture Radar

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The hydrological information at large area important to know the interaction between the land surface and the atmosphere. Now the synthetic aperture radars mounted on satellites such as the European Remote Sensing satellite(ERS-1) and the Japanese Earth Resources Satellite-1(JERS-1) are expected to observe the surface hydrological conditions in detail. This study focuses on the soil moisture, snow and land cover.(a)The backscattering coefficient measured by microwave sensors in affected not only by soil moisture but also other factors such as polarization, incident angle, sensor's frequency, surface roughness, soil composition etc. Based on the field experiments using the C-band scatterometer system, the microwave signatures of soil moisture were shown as follows :i.In case of the bare soil, as incident angle increases, the backscattering coefficient value decreases.ii.As incident angle increases, the soil moisture sensitivity increases while the correlation coefficient decreases.iii.T … More he better system combination is found to be the cross-polarization and incident angle at 20degree.(b)Microwave techniques offer important advantages for snow mapping. One is the all weather capability and hye other is the possibility to detect snow water equivalent directly. The theoretical and experimental study on the active microwave remote sensing of snow were conducted at Toyama, Nagaoka and Sapporo using the spaceborne SAR and gound surveying.The theory proposed by England in 1975 was applied to the microwave transfer in snow. The radiative transfer theory and Rayleigh scattering model were used to obtain the backscattering coefficient of snow. The theory is based upon several scattering dielectric layrs over the gound. The results of the measurement using the ground based scatterometer showed that the snow surface and the interface of snow layrs were quasi-specular. The model simulations showed that the effect of ground surface backscattering was not detectable because of the large dielectric loss of snow in Tpyama and Nagaoka and that the volume scattering was more inportant in those area.(C)A method for collecting drainage information and its accuracy was investigated using JERS-1 and ERS-1 SAR data, Landsat TM data and SPOT P-mode data obtained in Yata River Basin near Nagoya in Japan. The results were shown as follows :i.The mean backscattering coefficient is smaller in a water area than in the other land cover.ii.To delineate a water area, it is better to use the ERS-1 SAR data than the JERS-1 SAR data.iii.To identify boundaries clearly between various land covers except a water area is difficult by the use both of ERS-1 and JERS-1 SAR data. Less