Simulation Study On Application For THz Atmospheric Limb Sounder

Monitoring the Earth's atmosphere plays an important role in science such asnumerical weather prediction,natural disaster analysis and global climate change research.The terahertz frequency band has advantages of penetrating clouds and rain,not relying on the sun,and independent of the day–night cycle.Limb sounding is the most effective observation method for measuring the atmospheric vertical profiles.By scanning the tangent point of the atmosphere,vertical profiles of temperature,pressure,chemical species and winds can be measured with high vertical resolution.In this dissertation,the THz Atmospheric limb sounder?TALIS?which is designed by our team is studied:Spectrometer channels of TALIS are designed and their performance are evaluated based on the simulation.The influence of TALIS measurement errors on the retrievals are analyzed,and the performance comparison of TALIS and Aura/MLS?Microwave Limb Sounder?is also studied.In addition,extensive applications of THz limb sounder are researched.These studies are to provide support for the future development of satellite payload.Firstly,the channels of TALIS are designed and validate by performance evaluationin this dissertation.According to the system scheme of TALIS,the effects of trace gases in the atmosphere and their spectral lines in the THz band are analyzed.Then the positions of spectrometer channels of TALIS are given according to this analysis.The spectra of TALIS are modeled by ARTS?Atmospheric Radiative Transfer Simulator?and a further simulation is performed to estimate the precision?single scan and averaged data?of the main targets of TALIS?Temperature,O₃,H₂O,HCl,HNO₃,Cl O,N₂O,CO,NO,NO₂,HOCl,HCN,SO₂,Br O,HO₂,H₂CO and CH₃Cl?.Secondly,the effects of TALIS measurement errors on atmospheric composition retrievals and the comparison of TALIS and Aura/MLS are analyzed.By analyzing the possible measurement errors?instrument errors,calibration errors and a priori errors?of TALIS,combining with the method of parameters perturbation,the influence of measurement errors on TALIS retrievals are evaluated.The application performance of TALIS and MLS in four main products is compared,and the influence of technical parameter variation of TALIS on retrieval results is also studied.The results show that the FFT?Fast Fourier Transform?spectrometer used by TALIS is better than the filter spectrometer used in MLS.Although increasing the spectral resolution will make the sensitivity worse,TALIS is superior to MLS.The increase of system noise temperature of TALIS will obviously reduce the precision.The spectral resolution of TALIS is beneficial to improve the precision in the upper atmosphere.However,the increase of initial error will reduce the precision in the upper atmosphere.Finally,the new application and development direction of THz limb radiometer are proposed,including the potential of wind field measurement in middle and upper atmosphere and the design of a radiometer with a large bandwidth spectrometer.Based on the wind detection mechanism,the species which can be used for atmospheric wind measurement is proposed,and the performance of TALIS in measuring atmospheric line-of-sight wind speed is evaluated by simulation.For the 655 GHz and 2.06 THz bands which is suitable for atmospheric wind measurement,the effects of different spectral bandwidth and resolution on wind retrieval precision are studied.The design of using a 15 GHz bandwidth spectroradiometer to observe the atmosphere is put forward.By analyzing the spectral line distribution characteristics of 340 GHz frequency band,comparing the retrieval precision of 340 GHz radiometer and TALIS,it is proved that the 340 GHz radiometer can reach the performance of TALIS and has a good application prospect.