基于ENVISAT ASAR数据的水稻时域后向散射特征分析

    Analysis on temporal behaviour of rice backscatter based on ENVISAT ASAR images

    • 摘要: 该文结合2004年和2006年在江苏省里下河地区进行的水稻观测试验,采用多时相双极化ASAR APMode数据分析了水稻HH极化、VV极化和比值系数σ°HH/VV的时域变化特征及与水稻生长参数的相关关系。通过建立水稻HH、VV和σ°HH/VV的时相变化曲线,分析了水稻抽穗期前后雷达信号随水稻冠层、植株含水量及稻田水层变化的后向散射特征。同时,选择水稻叶面积指数、鲜生物量和水稻株高与含水量的乘积为水稻参数,采用线性回归相关分析,探讨了水稻HH、VV和σ°HH/VV与所选水稻参数之间的相关关系。结果表明,以水稻抽穗期为转折点,水稻各极化后向散射系数随水稻的生长呈现先增大后减小的变化趋势,与所选水稻参数的时相变化大体一致。水稻HH和VV极化后向散射系数与所选水稻参数的相关系数都在0.75以上,其中与水稻鲜生物量的相关系数在0.9以上。σ°HH/VV与水稻参数的相关关系显著,相关系数均在0.85以上,并且受水稻品种、种植方式和地理环境等差异的影响较小,因此可用于水稻参数反演的可靠变量。

       

      Abstract: Combined with field experiments of rice in Lixiahe region of Jiangsu Province in 2004 and 2006, temporal behavior of rice backscatter was analyzed based on multi-polarization advanced synthetic aperture radar(ASAR)data with incidence angle of 23o, together with the analysis of relationships between rice backscatter coefficient and rice growth parameters such as leaf area index, fresh biomass, and plant height×plant water content, for the further work on rice parameter inversion and research of rice backscatter physical mechanism. Meanwhile, temporal behavior of σ°HH/VV and relationships between σ°HH/VV and rice parameters were also analyzed. As a result, VV and HH backscatter before rice heading stage showed quite different temporal behavior from those after rice heading stage. σ°HH/VV increased with rice growth, and then decreased at ripening stage that indicated the noticeable difference between VV and HH backscatter in the whole rice cycle. The correlation coefficients of rice backscatter coefficient of VV and HH polarization and the chosen rice growth parameters all reached above 0.75, however, the correlation coefficient was above 0.9 between rice backscatter coefficient of VV and HH polarization and rice fresh biomass. Otherwise, the strong relationship between σ°HH/VV and rice growth parameters is observed in the paper with correlation coefficients of above 0.85, which shows that σ°HH/VV can be considered as a new variable in rice parameter inversion based on multi-polarization radar data.

       

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