An observational study on the evaluation of snow-covered area by remotely-sensed data with different spatial resolutions and on the snowmelt-runoff analysis

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To accomplish the objectives of the present study, the concrete contents of the analyses and the results obtained are summarized as follows.1.The snow index recently proposed was calculated by Landsat/ETM+ and was applied to the coniferous forests in Tsunan-town in Niigata prefecture. The threshold of LAI (Leaf Area Index) to distinguish between snow and coniferous forests using the snow index was estimated based on in situ field survey. As a result, it was clarified that the snow index could discern snow from coniferous forests if LAI was smaller than 4.(Shimamura et al., 2006).2.Effects of differences of the processes of direct measurements of LAI and their combinations on the estimation of LAI for planted stands of Japanese cedar (Cryptomeria japonica D.Don) were estimated by in situ field survey in Hinohara-village in Tokyo and Tsunan-town. The processes consist of selection of sample tree(s), sampling of leaves, and planimetry of leaf area. Each process has several methods, and th … More e differences of estimated LAI in each process were not so large. However, the accumulation of these differences led to as large as 40% of the estimated LAI, even in the planted stands of Japanese cedar which were taken care of such as pruning or thinning (Fujiwara et al., 2005).3.Snow surveys in Mt.Makihata and synchronized observations of the existence of snow with the passage of Landsat satellite were carried out in springs which made it possible to estimate the snow water resources in the Uono river above Muikamachi river discharge station. The estimated amount of snowmelt as revealed by the analyses of two scenes of Landsat/ETM+ was larger than the observed runoff. This implied the importance of precise analyses of snowmelt-runoff processes (Shimamura et al., 2005).4.The effect of the dependence of the satellite data on sun/sensor geometry (BRDF) for monitoring vegetation was evaluated. The vegetation in the succession stages after forest fire was investigated. The difference of Normalized Difference Vegetation Index (NDVI) of the value around 0.1-0.2 was caused by BRDF in relation to the sun/sensor geometry. Against BRDF, the reflectance of the near-infrared band normalized by the sum of other bands was most robust in the site where vegetation existed. Global Environmental Monitoring Index was most robust in the site where vegetation was scarce, while NDVI was strongly affected by BRDF in these sites (Hasegawa et al., 2006).5.The spatial representativity of the annual mean temperature of AMeDAS, which was important for snowmelt-runoff analyses, was investigated using the variogram. In the variogram, the value called as "range" was regarded as the measure of the spatial representativity. It was found that the annual mean temperature had the spatial representativity of at least 100km in all regions in Japan (Hadano et al., 2004). Less