Tomographic Retrieval Algorithm Of OH Radical In The Mesospheric Atmosphere

Hydroxyl OH is very important for humans to understand the chemical composition of the mesospheric atmosphere.OH radicals play an initial role in atmospheric photochemical reactions and initiate the entire oxidation chain in the atmosphere.Changes in the concentration of OH radicals determine the decline in ozone concentration in the atmosphere,fluctuations in tropospheric water vapor,changes in NOx and CO and other greenhouse gas emissions,and changes in the climate.The OH radicals also have a close relationship with the formation of polar mesospheric clouds.Polar mesospheric clouds can be used to measure the stability of the upper atmosphere and the asymmetry of the hemispherical climate.Precise detection and inversion of OH radical concentration and acquisition of OH radical distribution with high spatial resolution are of great significance for the study of greenhouse gases,changes in ozone concentration and even climate change.Internationally,there is a certain foundation for the detection of OH radicals in the middle and upper atmospheres based on high-resolution spatial heterodyne spectroscopy.We are still in the beginning in this respect.With the advancement of payload technology,the on-orbit limb detection mode that can simultaneously obtain high vertical resolution and high spatial coverage is more and more widely used,and the inversion algorithm for limb remote sensing also develops.With the development of OH radical detection technology system and payload,its inversion method is also continuously innovating and improving.On the basis of general limb inversion algorithm,the tomographic inversion algorithm compensates the defect of the low horizational resolution of the limb remote sensing to a certain extent.Combined with the multi-angle observation data of the detection instrument,it can restore the real OH radical space distribution to a greater extent.In this paper,the simulation and measured OH spectral data of spatial heterodyne spectroscopy tomographic spectrometer are taken as the object of study.For the purpose of obtaining high spatial resolution and ultra-high resolution tomographic data cubes,the emission mechanism of OH radical solar resonance fluorescence signal and radiation,improvements in radiative transfer model have been systematically studied with OH radical forward models,data simulation based on instrument characteristics,and OH tomographic inversion algorithms.The OH radical hyper-high resolution spatial heterodyne spectrometer based on the spatial heterodyne spectroscopy technique was used to detect the solar resonance fluorescence signal of the OH radical in the middle and upper atmosphere.The instrument has two orthogonal fields of view,each field of view to achieve sub-field imaging.In order to obtain the vertical profile of OH radical,this paper studies the forward model and retrieval algorithm of OH radicals in the middle and upper atmosphere based on the characteristics of the instrument.According to the characteristics of the detection target and the detection mode,a matching radiative transfer model is constructed,and on the basis of this,the corresponding retrieval algorithm is studied.To carry out such research requires the establishment of reliable and effective data sources.Because there is no suitable measured data,a simulation data source calculation flow has been established for this purpose.According to the instrument characteristics of the spatial heterodyne spectrometer,the radiance output from the radiative transfer model is used.The simulation of interferometric data between the subfields of view and the orthogonal fields of view is performed.The main work of the dissertation includes the following aspects:1.The background of the detection of OH radicals was introduced.The current status of OH radicals' detection on orbit and in ground base at home and abroad was investigated.The retreival algorithms for the existing OH radicals in the middle and upper atmospheres were summarized and was proposed.The idea combines multi-angle detection and the tomographic retrieval algorithm was proposed to obtain higher inversion accuracy.2.Conducted research on the mechanism of OH radical detection technology in the middle and upper atmosphere.Firstly,from the detection target,the emission mechanism of the OH radical solar resonance fluorescence signal in the middle and upper atmosphere was studied.To study the basic theory of spatial heterodyne technology,introduce the imaging mechanism of orthogonal and separate field of view in the dual field of view of the OH radical hyper-high resolution spatial heterodyne spectrometer in the upper and middle atmosphere,and study the interferometric data processing methods and simulation methods of the spatial heterodyne spectrometer.According to the observation mode of the instrument,the related theory of atmospheric radiative transfer and atmospheric remote sensing inversion are briefly introduced.3.Develop a forward model of OH radicals in the middle and upper atmosphere.Based on the emission mechanism of OH radical resonance fluorescence signal,combined with molecular spectroscopy theory,the fluorescence emission rate factors were calculated and the radiative transfer model SCIATRAN was modified to obtain a forward model for the OH radical in the middle and upper atmosphere.One-dimensional radiance simulation was performed using this model and OH Level 2 data of MLS,and sensitivity analysis was performed on observation geometry and aerosol parameters.In order to provide effective and reliable data sources,multidimensional radiance simulation and orthogonal radiance simulation were performed.4.Data construction based on forward model and experimental verification.According to the characteristics of the spatial heterodyne spectrometer,the output of the radiative transfer model is used as an input source for the simulation of the interferometric imaging interference data.Then according to the outfield experiment,the radiative transfer model was verified;according to the laboratory OH detection results,the instrument's detection capability was verified.5.Research on OH radical retrieval algorithm in middle and upper atmosphere.First of all,the spectral recovery preprocessing is performed on the inversion data source(ie,interference data)to simulate the complete data processing and inversion process.The inversion prior knowledge was constructed using the OH Level 2 data of MLS.Two commonly used inversion iteration methods are analyzed and compared,and the influence of the correlation coefficient on the inversion results is studied.Before the tomographic retrieval,the radiance data of the main field of view is corrected by using another field of view data,and a new two-dimensional radiance surface is constructed to be substituted into the tomographic algorithm.The error analysis of the tomographic algorithm was compared with the one-dimensional inversion algorithm.The tomographic inversion algorithm was used to reduce the inversion error from aprior information,verifying the feasibility of the tomographic algorithm and improving the inversion accuracy.Based on the above research,this study has innovations in the following aspects:1.A complete forward model of OH radicals in the middle and upper atmosphere has been constructed for the first time in China.2.For the OH radical ultra-high resolution spectrometer in the middle and upper atmosphere,a complete interferometric data processing method and inversion algorithm was established,and a complete data simulation model from the radiation transmission model to the spectral data was established to provide theoretical basis and data foundation for future applications.3.A tomographic inversion algorithm for OH radical ultra-high resolution spectrometer in the middle and upper atmosphere was realized.And the retrieval error is redudced to less than 5%.