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Monitoring of Plant growth and Snow Cover in the Ishikari Plains by Microwave Remote Sensing

微波遥感监测石狩平原植物生长和积雪

基本信息

批准号：
08650439
负责人：
AWAKA Jun
金额：
$ 1.41万
依托单位：
Hokkaido Tokai University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1996
资助国家：
日本
起止时间：
1996 至 1998
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-08650439/
关键词：
Remote Sensing JERS-1 SAR Microwave Scattering Cross Section Snow Cover Plant Growth Rice Paddy 衛星リモートセンシング光学データ稲

项目摘要

This study started with the purpose of demonstrating the usefulness of microwave Remote Sensing for a monitoring of wide area through the investigation of plant growth and snow cover in the Ishikari plains by a microwave Synthetic Aperture Radar (SAR) onboard the Japanese Earth Resource Satellite 1 (JERS-l) and through the development of the algorithm for extracting information about plant growth and snow cover.The Normalized Radar Cross Section (NRCS) of rice paddies in the Ishikari plains shows a large value in sumner and in winter. Since NRCS is proportional to the received power of the radar, a large NRCS means that the strength of radar echo becomes large. A large NRCS in summer is understandable because of a volume scattering from growing rice, but a large NRCS in winter is a puzzle because the literatures reported the contrary. To solve this puzzle, the later part of this study was devoted to a theoretical investigation.Since JERS-l SAR uses a low frequency (1.275 GHz) of L band … More microwave, dry snow cover is almost transparent to the wave, which means that the attenuation of the wave due to dry snow cover can be negligible. Dry snow cover, however, has a refraction effect on the wave making a steeper incidence from snow to the soil. This steeper incidence increases NRCS because NRCS depends on the angle of incidence. (Here, the roughness of soil surface is assumed to be the same for with and without the snow cover, and the water content of soil is also assumed to be the same for with and without the snow cover.)When snow cover becomes wet, NRCS decreases because the water in the snow attenuates the wave. But the wet snow supplies water to the soil, making the water content of soil increase. When the water content of soil increases, the impedance of soil increases ; the increased impedance of soil enhances the impedance mismatch between snow and soil, so that the scattering from the soil increases. For wet snow cover, the above two competitive mechanisms, viz. , attenuation due to wet snow and increase of scattering due to a larger water content of soil, can make it possible that NRCS with snow cover is larger than that without snow cover.The above method for analyzing the L band SAR data may be extended to the analysis of higher frequency data when the volume scattering effect is included in the analysis Less

本研究的目的是通过日本地球资源卫星1号（JERS-1）上的微波合成孔径雷达（SAR）对石狩平原的植物生长和积雪进行调查，并通过开发提取植物生长和积雪信息的算法，来证明微波遥感在大面积监测中的有用性。石狩平原稻田的NRCS在夏季和冬季表现出较大的值。由于NRCS与雷达的接收功率成比例，因此大的NRCS意味着雷达回波的强度变大。夏季NRCS较大是可以理解的，因为水稻生长产生的体积散射，但冬季NRCS较大是一个谜，因为文献报道的情况相反。为了解决这一难题，本文的后半部分对JERS-1 SAR进行了理论研究 ...更多信息在微波中，干雪覆盖对波几乎是透明的，这意味着由于干雪覆盖引起的波的衰减可以忽略不计。然而，干燥的积雪对波有折射作用，使波从雪到土壤的入射角更陡。由于NRCS取决于入射角，因此这种更陡的入射角增加了NRCS。(Here，假定有无积雪时土壤表面的粗糙度相同，也假定有无积雪时土壤的含水量相同。）当雪盖变湿时，NRCS减小，因为雪中的水衰减了波。但湿雪给土壤提供水分，使土壤含水量增加。当土壤含水量增加时，土壤阻抗增大，土壤阻抗的增大加剧了雪与土壤之间的阻抗失配，从而使土壤的散射增强。对于湿雪盖，上述两种竞争机制，即湿雪引起的衰减和土壤含水量增大引起的散射增加，使得有雪盖时的NRCS大于无雪盖时的NRCS。当分析中考虑体散射效应时，上述分析L波段SAR数据的方法可以推广到更高频率数据的分析。