Study On Measurement Technology Of High Spectral Total Atmospheric Transmittance

The atmospheric transmittance is an important parameter to reflect the character-istics of atmospheric transfer.It is of great significance in the study of atmospheric radiation,remote sensing of earth resources,air quality monitoring and target identifi-cation.It is difficult to take into account the needs of high resolution and portable mobile applications such as the Sun Photometer and the Fourier Transform Infrared Spectrom-eter.Based on a high sensitivity spectral detection technology,the direct measurement of the total atmospheric transmittance is studied in this paper.Several important results were obtained as following:(1)Based on the laser heterodyne technology,a set of high resolution trans-mittance direct measurement system was established together with a target tracking device.Detailed noise analysis of every vital process in the measurement system is p-resented,several strategies were presented to optimize the performance of the system,in which the signal-to-noise ratio is as high as 513.2 while the spectra resolution is up to 0.006cm-1.(2)The calibration of the system is carried out by using the Langley-plot calibra-tion method,which is based on the high-resolution atmospheric transmittance measure-ment system.The field measurement and comparative analysis of two typical seasons in spring and autumn in Hefei were carried out and the direct measurement data of the total atmosphere transmittance of the 4.497 micron band were obtained.According to the comparison between the results of heterodyne measurement system and that of soft-ware MODTRAN 5 calculation,good agreement was obtained.It is show that the laser heterodyne detection system is very promising and could be used in the atmospheric detection.(3)In the clear and sunny weather conditions,the variation range of the atmo-spheric transmittance in the Hefei is 0.156?0.708 and the mean and standard deviation are 0.435 and 0.128,respectively.The variation range of atmospheric transmittance in autumn was 0.192?0.639 and the mean and standard deviation were 0.397 and 0.128,respectively.From the total atmosphere transmittance through the view of probability distribution of the rate of less than 0.3 probability were 15%(Spring),11%(Autumn),through the probability distribution in the 0.3?0.5 were the 53%(Spring),63%(Au-tumn),through the probability distribution in the 0.5?0.7 were the 32%(Spring),26%(Autumn).