CE318型太阳光度计标定方法初探

An Introductory Study on the Calibration of CE318 Sunphotometer

初步探索了CE318型太阳光度计的室内和野外标定方法,并对两种方法的标定结果进行对比。基于积分球辐射源的辐亮度标定方法,对CE318型太阳光度计不同波段天空散射辐射通道进行标定实验;分别采用Langley标定法和标准仪器相对标定方法,对CE318型太阳光度计的不同波段太阳直接辐射通道进行了标定实验。实验结果显示:天空散射辐射通道的标定结果在670nm,870nm和1020nm波段与仪器出厂时给定的标定结果偏差不超过6%,而440nm波段处得到的标定结果要高于出厂时给定的结果,偏离幅度约18.9%。太阳直接辐射各通道的标定结果普遍大于出厂时给定的结果,说明滤光片老化较为严重,需要进行更换,以保证观测精度。由于标准仪器相对标定方法对太阳直接辐射通道的标定结果明显优于Langley法,因此利用标准仪器相对标定方法对中国气象局太阳光度计站网仪器进行定期标定更能够保证仪器观测数据的准确性。

The indoor and field calibration methods of CE318 sunphotometer are mainly explored and the calibration results of the two methods are compared. Based on integrating sphere radiation calibration method, an experiment is carried out for the calibration of the sky scattering radiation channels at eight different wave bands of CE318 sunphotometer. Langley calibration method and standard instrument relative calibration method are used to calibrate sun direct radiation channels at different wave bands of CE318 sunphotometer. The results of this experiment show that the calibration results of sky scattering radiation channels at 670 nm, 870 nm, 1020 nm and the original calibration of the same instrument are fundamentally equal with the discrepancy less than 6 %. It has high reliability. Unfortunately the result of the wave band of 440 nm is higher than the original calibration, and the departure range is about 18.9%. Based on the calibration results, it can be concluded that there are good feasibility and reliability in using integrating sphere for calibrating the sky scattering radiation channels. However, there is a little difference between the calibration results and the original calibration. Considering the fact that aging filters might be led to by using conditions and measurement for long periods outdoors, some aerosol particles may fall on the filters which are inside the sensor head, even because the filters run very long time, so the filters are made broken. Generally speaking, the calibration results of the sun direct radiation channels are slightly larger than the original calibration. The results show that the filters of some channels are aging, so it is necessary to replace them to ensure observation precision. In addition, the comparisons between the Langley method and standard instrument relative calibration method are made. It shows from the comparison results that good weather conditions on the day of calibration are required by the Langley method, which include clear sky, cloud-free and stable atmosphere, and very accurate standard instrument is required by the standard instrument relative calibration method. Because the standard instrument relative calibration method is more advantageous than the Langley method from the comparing results, the standard instrument relative calibration method is employed by the present study to calibrate the CE318 sunphotometer in the CARSNET（China Aerosol Robot Sunphotometer NETwork） of China Meteorological Administration to guarantee the precision of the observation data.