基于辐射传输的M'波段大气透过率实测和误差分析

采用自制的M'波段（4.605~4.755 m）红外辐射测量系统对阿里观测站、德令哈观测基地和怀柔观测基地的大气辐射进行实地测量，并对结果进行拟合和误差分析。首先，基于黑体定标结果和辐射传输方程，得到输出有效读数与平均大气透过率和天顶角的关系公式；在三个站点对不同天顶角下的大气红外辐射进行扫描测量，利用上述公式，拟合出M'波段平均大气透过率。结果表明，三地透过率的加权平均值分别为0.805、0.758、0.650，透过率随时间的起伏分别为0.081、0.250、0.073，高海拔的阿里观测站透过率最高。用MODTRAN软件模拟的平均透过率分别为0.851、0.805、0.615，与实测结果接近；误差分析表明:有效读数越大，传递误差越小，此方法的理论误差优于10%。文中提供了一种不依赖气象数据，实时获得大气透过率的方法。

Measurement and error analysis of the atmospheric transmissivity in M' band based on radiative transfer

The atmospheric infrared radiance was measured at Ali, Delingha and Huairou observing station using a self-made measurement system in the infrared M'(4.605-4.755 m) band. Based on the blackbody calibration and the radiative transfer equation, a simplified relation between the effective output value, the average zenith atmospheric transmissivity and the zenith angles can be obtained. Atmospheric infrared radiation of different zenith angles at three Astronomical Station were measured and scanned, and the above formula was used to fit the average atmospheric transmissivity of the M'band. The measurement results show that the weighted average values of the atmospheric transmissivity in the three places are 0.805, 0.758 and 0.650 respectively, with the fluctuations of 0.081, 0.250, and 0.073 respectively. The average transmissivity simulated by MODTRAN software was respectively 0.851, 0.805, 0.615, which was close to the results from the measurement. The error analysis shows that the propagation error decreases with the increasing effective output value. The theoretical error of indirect measurement method was analyzed to be less than 10%. This paper provided a on-site and real-time measuring method of the atmospheric infrared transmissivity independent of meteorological data.