Study On Temporal And Spatial Distribution Of Atmospheric HNO₃ And HCl Based On Ground-based High-resolution Fourier Transform Spectroscopy

Stratospheric Ozone?O₃?in the atmosphere can resist ultraviolet rays and reduce the damage of the earth's organisms from ultraviolet rays,which is essential for the survival and development of human beings.However,depletion of the stratospheric ozone layer is one of the most prominent environmental problems in the past 40 years.A variety of trace gases in the atmosphere can have a certain effect on the stratospheric O₃ loss.Nitric acid?HNO₃?and hydrogen chloride?HCl?are the reservoir species of active nitrogen and active chlorine in the stratosphere,which will indirectly participate in the O₃ destruction process.Therefore,it is of great significance to know the contents,temporal and spatial distribution characteristics,seasonal and annual changes of gases HNO₃ and HCl in the atmosphere for the study of the protection and repair of the ozone layer.Ground-based high resolution Fourier transform infrared spectroscopy?FTIR?technology has the advantage of high accuracy and precision in detection of ambient atmospheric trace gases.In this paper,FTIR spectroscopy is used to study the temporal and spatial distribution and variation characteristics of HNO₃ and HCl in the atmosphere.The mid-infrared direct solar absorption spectra are obtained based on ground-based observations to study atmospheric HNO₃ and HCl retrieval algorithms and error analysis methods,retrieve the vertical profile and total columns of HNO₃ and HCl,and analyze the vertical distribution information of the two gases;the time series of HNO₃and HCl column amounts in the three years from 2017 to 2019 are obtained by retrieval,seasonal and annual variation characteristics of the total columns and the stratospheric partial columns of HNO₃ and HCl are analyzed,and make a comparison with satellite observations.The spectral retrieval error of atmospheric HNO₃ is 12.16%.The error mainly comes from the systematic error caused by the molecular spectral line strength parameter,which accounts for 58%of the total error sources.The vertical profile distribution and averaging kernels information of HNO₃ indicate that in the stratosphere of²0-40km,the concentration of HNO₃ is higher and the retrieval sensitivity is greater.Atmospheric HNO₃ total columns in Hefei area shows obvious seasonal variability in2017-2019,with higher concentration in spring and lower concentration in autumn.The amplitudes of seasonal changes in each year are 1.35×10¹⁶molecule cm^-2,1.24×10¹⁶molecule cm^-2 and 9.17×10¹⁵molecule cm^-2 respectively.It shows a downward trend year by year,with an annual change rate of-5.12%per year.The results of comparison and verification with the satellite indicate that the ground-based FTIR measurements and MLS?Microwave Limb Sounder?satellite observations show the same seasonal variability,and the satellite observation values are generally lower than the ground-based measurements.The correlation coefficients between the atmospheric HNO₃ total columns and the stratospheric partial columns of ground-based FTIR observations and MLS satellite observations are 0.85 and 0.86,respectively,indicating that the ground-based measurements and satellite observations have a good consistency.The atmospheric HCl spectral retrieval error is 10.09%.The error mainly comes from the systematic error caused by the molecular spectral line strength parameter,accounting for 98%of the total error sources.The retrieved profile and averaging kernels of HCl show that the concentration of HCl is higher in the height range of about25-50km,the concentration is smaller when the height is less than 20km,and the retrieval sensitivity is higher in the height range of about 10-30km,with the highest sensitivity at about 20km altitude,which demonstrate that HCl is mainly distributed in the stratosphere.The time series of HCl total columns from the year of 2017 to 2019has obvious seasonal variability.The concentration in spring is larger,and the concentration in autumn and winter is lower.The amplitude of seasonal changes in each year are 1.78×10¹⁵molecule cm^-2,2.05×10¹⁵molecule cm^-2 and 1.57×10¹⁵molecule cm^-2,the rate of annual change is-5.17%per year.The comparison between the ground-based observation results of HCl and the satellite observation results shows that the ground-based FTIR measurement and the MLS satellite observing data have the same seasonal variability,and the satellite observation values are generally smaller than the ground-based measurement values.The correlation coefficients between the ground-based FTIR observations and the MLS satellite observations of the HCl total columns and partial columns are 0.71 and 0.77,respectively,which indicating that the ground-based observations and satellite observations have a good consistency.Finally,we make a comparative analysis of the stratospheric HNO₃ and HCl partial columns with the stratospheric O₃ partial columns.The results show that the atmospheric stratosphere HNO₃,HCl and O₃ in Hefei have similar seasonal variability,The ratio between HNO₃ and O₃,HCl and O₃ are all greater than 0,and stratospheric HCl and O₃ have a strong positive correlation,the correlation coefficients are 0.82 and0.86,respectively.It shows that in the non-polar Hefei area,the direct effects of atmospheric HNO₃ and HCl on stratospheric O₃ are not obvious.The research results in this paper demonstrate that the ground-based high-resolution FTIR spectroscopy has the ability to accurately measure the vertical profile,total columns and partial columns of atmospheric HNO₃ and HCl,and has the reliability and accuracy to study the spatial and temporal distribution and variation characteristics of trace gases such as HNO₃ and HCl which have a influence on the loss of O₃ in the stratosphere.