An algorithm to derive the effect of the land surface on the emergent radiation from the top of the atmosphere in the coastal zone is proposed. The surface is simulated by checkerboard type of terrain composing pixels, either land or ocean. The Look-Up-Table method is used for the atmosphere-surface correction, where two parameters based on the diffuse transmission and reflection function of the atmosphere are introduced to investigate the contribution of adjacent pixels. These parameters are independent of the surface reflection properties. The ocean surface is in accordance with the Cox and Munk model surface, whereas that of land is assumed to be Lambertian. The upwelling radiation emerging from the top of the atmosphere is expressed by a sum of radiative interactions between surface and atmosphere, and it is calculated using these interactions until the sum is converged. An example of numerical simulation is shown at wavelength of 0.56μm, which corresponds to the center wavelength of the shortest channel of ASTER on EOS-AM 1. The dust like model is used for the aerosols, whereas the land surface albedo is 0.2 or 0.4. The ocean wind is 5 m/sec and the refractive index is 1.333. The effect of the land surface on the radiance over the ocean is stronger just off the coastal zone and decreases with the increase of distance away from the land exponentially. It depends upon the solar zenith angle and atmospheric condition as well. The present new version enable us quantitatively to discuss radiative transfer over the non-uniform composite surface including coastal zone.
Thermal infrared emissivity of sand, sampled in the Muus Desert in China, have been measured under controlled soil moisture content in order to obtain quantitative relationship between soil moisture arid spectral emissivity. Spectral emissivity of the dried sand, which contains large amounts of quartz and feldspar, shows a depression in the 8-10μm range. However, the emissivity increases in the 8-10μm range when there is an increase in the soil moisture content, and no changes are observed in the 11-13μm range. In some cases, however, this phenomenon is not clear because of temperature estimation error in the sample. An error of 1°K in temperature estimate causes about a 2% emissivity error and less than 0.5% error in the emissivity ratio in the thermal infrared. The emissivity ratio of averaged ASTER TIR channels (10, 11, 12):(13, 14) is proposed to be an indicator of the soil moisture content. This ratio increases by about 3% with increase in moisture content from 0 to 2% in weight.
Recently, microwave remote sensing has become a strong tool for monitoring the surface of the earth. As a potential application, the monitoring of the surface distribution of soil moisture content is an important factor in hydrology. The differential scattering coefficient data obtained from a satellite borne scatterometer depend on the complex dielectric constant, which is related to the moisture content in the soil. This paper describes the results of the investigation of the soil moisture content characteristics of Kanto loam. The dielectric constant of wet soil is measured by using the S-parameter method which has a large aperture waveguide compared with the wavelength. In order to model the characteristics of dielectric constant to soil moisture content, two adjustable parameters α and β in the semi-empirical model proposed by F.T. Ulaby et al. are determined from the results of above experimental data. The parameter a agrees with the a of the soil in the USA, but the parameter β is different from the β in the USA. From the result of comparison between the measured result by Hirosawa et al. and our result, it is noted that the real part of the complex dielectric constant does not agree well. Then the Fresnel reflection coefficient of Kanto loam is also measured by using a modified detecting method of reflected wave. In the general case, the scattering coefficient is directly proportional to the power reflectivity. A good agreement is obtained between the reflection coefficient calculated by the semi-empirical model and the above result. So it is concluded that soil moisture content of Kanto loam can be estimated by using the semi-empirical model based on our experimental results by taking the roughness and the incident angle into account.
Seasonal change and passing year change of vegetation area for 20 years are investigated by pattern decomposition method and we make a study of vegetation vigor using pattern decomposition coefficients. Pattern decomposition method enable to reduce multi-dimensional satellite data into three-dimensional data which directly related to spectral pattern of standard land cover objects, namely water, vegetation and soil. For analysis of vegetation area change, vegetation area is extracted by classification analysis of land cover types. Validation of classification results was performed using detailed land use data of Nara city in 1985. It is made clear that 1) ratio of evergreen forest to vegetation area in Kansai district is found to be 38% from the seasonal change analysis on 1987 data, 2) the decrease of vegetation area of Kansai district and Keihanna area in Kansai district from 1975 to 1995 are about 10% and 20% of vegetation area on 1975, respectively, 3) vegetation decomposition coefficient represents information from only vegetation area in a pixel while NDVI is affected by the other land cover such as soil in a pixel, and 4) the vegetation vigor change from 1985 to 1995 is strongly related to average temperature change. Vegetation change and vegetation vigor are well analyzed by pattern decomposition method.
A satellite image database was developed for global wetland mapping. A lot of JERS-1 OPS and SAR images were collected over 80 test sites. A database management system of client server type was constructed on the PC network. We can select suitable image combination by using this system which draw rectangle area or browse imagery of satellite on a blank map.