Development And Application Of Shipboard Sun-Photometer

The diresct radiation of the sun will be attenuated when passing through atmosphere due to absorption and scaterring.It is necessary to remove the influence of atmospheric transmission parameters to obtain the characteristics of the sun radiation.Key parameters of radiation transfer,atmospheric transmittance,precipitable water vapor and aerosol optical thickness for instances,play an important role in many research fields,such as aerosol optical characteristics analysis,optical remote sensing,laser ranging and satellite inversion verification.Because of the application values mentioned above,traditional sun-photometer is widely used in ground-based remote sensing of atmospheric transmittance,precipitable water vapor and aerosol.But the ocean covers 70%of the earth’s surface,it is urgent to develop a device that can measure the atmospheric optical parameters precisely on shipboard platform for the study of atmospheric radiation and climate change.Our research group developed a novel shipboard sun-photometer with a new tracking method.The sun can be tracked on shipboard platform with an accuracy better than 1’.This new sun-photometer could obtain radiation information in nine spectral bands,as 400,440,532,550,780,870,940,1050,1064 nm,at once.Through which the aerosol parameter like precipitable water vapor can be retrieved from direct solar radiation measurement on shipboard platform,which provides a new technical means to measure atmospheric optical parameters at sea in China,and lays a solid foundation for space remote sensing,climate change and atmospheric environment research.The research content of this article is introduced as follows:(1)The instrument hardware development process is described in detail,including the instrument’s mechanical structure,two-dimensional turntable,control system,gyro stabilization platform and temperature control module.Following the hardware structure block diagram of the shipboard sun-photometer,the type selection and technical details of the instrument’s functional modules are described.(2)Spectrometric measurement system is introduced based on the integrated design of spectrometric measurement system.The structure and operation flow of spectrometric measurement system are analyzed specifically.The influence of stray light and detector saturation on the measurement results are thoroughly considered with corresponding improvement approaches.(3)Image tracking algorithm are described in detail by describing the structure and basic characteristics of the two imaging systems.The methods of solar image processing,such as image correction,edge detection and centroid extraction,are introduced.The theoretical tracking accuracy of the image tracking system can reach 0.744’.The tracking algorithm is introduced and verified.(4)In the marine atmospheric parameters measurement application,the Langley calibration method and the improved Langley method were used to calibrate the bands without atmospheric molecular absorption and water vapor absorption respectively.Our instrument has been used for long-term observation in the Bohai Sea area,and some variation rules of atmospheric transmittance,precipitable water vapor and aerosol optical properties have been obtained.Theresults were compared with CART software,DTF sun-photometer and POM-01 MKⅢ sun-photometer.The reliability and stability of the instrument’s atmospheric parameters measurement is proved at sea under a moving non-stable platform.