地基太阳光谱辐照度计的余弦误差影响及其校正方法

Cosine Error Influence of Ground-based Solar Spectral Irradiance Meter and Its Correction Method

针对自研的太阳光谱辐照度计入射光学系统的结构特征,分析了引入余弦误差的因素,研究了直、漫射辐照度以及漫射-总辐射比的余弦校正方法,开展了实验室余弦响应特性测量和多种仪器的敦煌外场比对试验.结果显示,余弦误差与积分球入口黑色阳极化内壁及结构有关,在入射角为60°时,440nm、500nm、670nm和870nm波段太阳光谱辐照度计的余弦误差为4.3%～9.1%;由太阳光谱辐照度计获取的直射辐照度反演得到的大气光学厚度受到余弦误差的严重影响,余弦校正前后与CE318太阳光度计反演结果相比,偏差分别为0.11～0.13和小于0.012;基于天空辐亮度各向同性分布假设,余弦校正后四个波段漫射辐照度数值提升6.8%～10%.基于天空辐亮度分布数据,提出了一种漫射辐照度的精确校正方法,仿真结果显示,余弦校正后的漫射辐照度与理论数据一致,初步验证了该方法的可行性.

According to the structural characteristics of the entrance optics of self-developed solar spectral irradiance meter,the factors that introduce cosine error were analyzed.The cosine correction methods of direct irradiance,diffuse irradiance and diffuse-to-global ratio were studied.Laboratory measurements of cosine characteristic of solar spectral irradiance meter and a field campaign in Dunhuang with a variety of instruments involved were carried out.The results show that the cosine error is related to the structure and the black anodized inner wall of the input aperture,and it ranges from 4.3%~9.1%at the incident angle of 60°at 440 nm,500 nm,670 nm and 870 nm.Atmospheric optical thickness of the four bands retrieved from the direct irradiance obtained by solar spectral irradiance meter is severely affected by the cosine error,and the deviation of the atmospheric optical thickness before and after cosine correction is 0.11~0.13 and smaller than 0.012,respectively,compared with the CE318 sun photometer inversion results.Four-band diffuse irradiance increases by 6.8%~10%after cosine correction by assuming an isotropy distribution of sky radiance.Based on the sky radiance distribution data,an accurate correction method for diffuse irradiance was proposed.The simulation shows that the diffuse irradiance after cosine correction is in good agreement with the theoretical result,which proves the feasibility of the method.