詳細な積雪分布観測 のための偏波レーダ活用技術開発

由于雪是一种与能量通量、风、湿度、水汽和气压结合在一起的高动态介质，利用多频SAR数据对积雪覆盖区域进行综合观测可以在绘制和监测积雪特性和动力学方面发挥重要作用。本研究旨在评估L波段星载合成孔径雷达探测季节性积雪区域的能力。利用日本的ALOS/PALSAR系统研究了雪山生态系统后向散射的季节变化。这项研究的重点是利用全极化散射观测，最大限度地获取积雪季节变化的信息。选定的研究地点是新泻县南部的内沼县。该地区位于日本阿尔卑斯山的北缘，由于冬季季风从西伯利亚吹到日本群岛，这里的降雪量是全国最大的。本文对L波段信号的矢量散射信息及其雪致变化进行了初步研究。地形和积雪厚度对合成孔径雷达信号的影响是新发现的。根据极化参数的季节性变化特点，利用信息融合的方法，提出了一种新的雪域地图绘制方法。结合偏振指数可以很好地识别积雪范围。这项研究表明，L波段的全极化星载合成孔径雷达，如ALOS-2，将提供足够的季节性降雪信息。

Since snow is a highly dynamic media in conjunction with energy fluxes, wind, moisture, water vapor, and pressure, integrated observation of snow-covered areas from multi-frequency SAR data can play an important role in mapping and monitoring snow properties and dynamics. This study aims to evaluate the capability of L-band space-borne Synthetic Aperture Radar (SAR) for detection of seasonal snow-covered areas. The seasonal change of backscattering from a snow-covered mountainous ecosystem was studied using the Japanese ALOS/PALSAR system. This study places the focus on utilization of the fully polarimetric scattering observation, maximizing information on the seasonal changes of snow-cover. The selected study site is Uonuma area in Southern Niigata Prefecture. This area is on the northern edge of the Japanese Alps and has some of the heaviest snowfall in the country due to a winter monsoon blowing from Siberia to the islands of Japan.In this study, vector scattering information of L-band signal and its snow-induced changes have been originally investigated. The effect of topography as well as snowpack thickness on SAR signal has been newly discovered. Based on the characteristic seasonal changes of polarimetric parameters, a new method to map snow-covered areas has been developed using an information fusion approach. Snow extent can be identified successfully by combining polarimetric indices. This study has elucidated that the L-band fully polarimetric spaceborne SAR, such as ALOS-2, will provide sufficient information on seasonal snow.