表面粗糙对渤海海冰热红外辐射方向特征的影响研究

Study on the impact of surface roughness on the infrared radiation direction of sea ice in the Bohai Sea

热红外遥感技术使大范围、快速地监测渤海海冰表面温度成为可能。然而,目前绝大多数遥感器都是小视场角的,只对海冰在某个方向上的辐射能量进行了测量。由于自然界的海冰大多数都是高低起伏的、不平坦的,如果近似地认为遥感像元尺度内各部分温度是相同的,有时会带来较大误差。在盛冰期的渤海辽东湾东岸固定冰区,分别用3D激光扫描仪、热红外成像仪和自计温度计测量了渤海海冰的表面形状、辐射亮温和真实温度。结果表明,由于海冰表面粗糙,会形成三维非同温像元。同时,也会导致传感器在粗糙海冰的各个部分的局部观测天顶角与整体观测天顶角有所不同,造成粗糙海冰与平整海冰的方向辐射特征有较大差异,平整海冰更接近理想平面,粗糙海冰更接近朗伯面。

Thermal infrared remote sensing make it possible to rapidly monitor the surface temperature of sea ice in the Bohai Sea. However, most sensors are small angle of field, and the radiation energy obtained by those sensors is always from a certain direction. Considering that the sea ice surface morphometric is rough, if we as- sume that the temperatures of sea ice pixels are homogeneous, hence, it may cause large errors to estimate sur- face temperatures of sea ice by using infrared remote sensing images. In this study, the surface morphometric of sea ice, brightness temperature of sea ice surface and the temperature of surface layer have been measured through the 3D laser scanner, thermal infrared imager and auto-record thermometer, respectively. The results show that the 3D structural pixels can emerge on the remote sensing scales for the reason of sea ice surface rough- ness. Meawhile, the sea ice roughness also could make a difference between the zenith of sensor of the inner part and the zenith of sensor of the whole pixel, and cause the difference between the directional characteristic of radi- ation of rough sea ice and the flat sea ice. The characteristic of directional radiation of fiat sea ice is close to ideal plane, and the characteristic of directional radiation of rough sea ice is close to lambert body.