The characteristics of a level sea-ice multiangle reflection spectrum in the Bohai Sea
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摘要: 近些年来,遥感技术在渤海海冰的监测中发挥了举足轻重的作用。海冰的反射特征是利用光学遥感监测海冰的基础。在晴空条件下,对盛冰期渤海辽东湾东部3种典型的平整海冰的半球-方向反射率因子(hemispherical directional reflectance factor,HDRF)进行了测量,并计算了相应的各向异性因子(anisotropy factor,ANIF),结果表明,只有在太阳光入射主平面内的前向反射方向附近,半球-方向反射率因子与各向异性因子才会迅速增加,而在其他方向上两者的变化不明显。平整海冰的厚度和内部结构等因素会影响HDRF和ANIF随波长变化的特征,在350~1 350 nm波段,厚度较小且表面光滑的平整海冰的HDRF值相对较小,而厚度较大的平整海冰的HDRF值相对较大。在350~950 nm波段,厚度较小且表面光滑的平整海冰ANIF相对较大,而厚度较大的平整海冰的ANIF值相对较小。以上结果充分说明海冰对太阳光入射辐射的反射是冰-气界面的反射与冰体内部的散射的综合结果。
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关键词:
- 渤海海冰 /
- 遥感 /
- 多角度 /
- 半球-方向反射率因子 /
- 各向异性因子
Abstract: In the last decades,the remote sensing technology has played a crucial role in the monitoring of the sea-ice in the Bohai Sea. The reflection characteristics of the sea ice are the fundamentals of sea-ice monitoring based on an optical remote sensing. The hemispherical-directional reflectance factor (HDRF)of three paradigmatic classes of level sea-ice collected from the eastern Liaodong Bay during the sea ice maximum is measured under cloudless sky conditions,and related anisotropic factor(ANIF)is also calculated thereafter. The results show that the hemispherical-directional reflectance factor and the anisotropic factor can increase rapidly only near the forward reflection direction within the principle plain of solar incident,while in other viewing directions,the variations of these two factors are insignificant. In addition,the thickness and inner structure of level sea-ice can affect the characteristics of the HDRF and the ANIF with varying wavelength. In the band of 350-1 350 nm,thin level sea-ice with a smooth surface has a relatively small HDRF,and thick level sea-ice has a relatively large HDRF. But in the band of 350~950 nm,absolute conclusions are drawn,thin level sea-ice with the smooth surface has a relatively large ANIF,and thick level sea-ice has a relatively small ANIF. These results suggest that the sea-ice reflection to the solar incident radiation is the combined consequent of ice-atmosphere interface reflection and internal scattering of sea ice. -
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