Study On Direct Channel Calibration Method Of Multi Band Solar Radiometer

Solar radiation plays a very important role in the earth's ecological environment and climate change.In recent years,the observation of atmospheric environment has become a hot topic.The optical characteristics of atmospheric aerosols,the temporal and spatial distribution of water vapor and aerosols,the concentration of various pollutants,and many factors affecting the quality of the earth's atmosphere and ground environment need to obtain information through the accurate observation of solar radiometer,and the premise of accurate observation is the accurate instrument calibration.Because the traditional Langley calibration method needs strict environmental requirements,and there is no calibration site that fully meets the requirements in China,improving the calibration method has become a feasible scheme to improve the calibration accuracy.Based on the multi band solar radiometer independently developed by the unit,this paper proposes a pre calibration data filtering algorithm,which aims to screen the data measured during the period of unstable atmosphere in the calibration measurement day,and improve the reliability of the data participating in the calibration by reducing the influence of atmospheric environmental factors,so as to improve the calibration accuracy.The calibration observation experiment was carried out with the instrument in Lijiang plateau,Yunnan Province,and a total of 50 days of observation data were obtained,which completed the calibration work for the instrument.Through the analysis of a large number of data,the appropriate screening threshold is obtained,and the calibration results after screening are compared with the traditional methods.The results show that the average distribution interval of calibration values of each channel after screening is reduced by70.4% and the standard deviation is reduced by 65.4%;Finally,the calibration results are screened again by statistical method to obtain the calibration constant of the instrument.According to the measured data samples,it is verified that the relationship between aerosol and wavelength conforms to the quadratic fitting model in log domain;The single channel and dual channel methods of the improved Langley method are used to calibrate the water vapor channel respectively.The results of the single channel method and the dual channel method with different auxiliary bands are compared.It shows that 870 nm is more suitable as the auxiliary band of the dual channel method,and the calibration results of the dual channel method and the single channel method have little difference under the condition of fine weather,so they can be used for calibration;Finally,the total amount of water vapor in the calibration observation day is inversed,and the results are in line with the expectation.The research of this paper has completed the reliability screening of multi band solar radiometer calibration data,which has important reference significance for the self calibration inspection of radiometer in China.