Retrieval of Stratospheric HNO3 and HCl Based on Ground-Based High-Resolution Fourier Transform Spectroscopy

Vertical profiles and stratospheric HNO3 and HCl columns are retrieved by ground-based high resolution Fourier transform infrared spectroscopy (FTIR) remote sensing measurements at the Hefei site in China. The time series of stratospheric HNO3 and HCl columns from January 2017 to December 2019 showed similar annual variation trends, with an annually decreasing rate of (-9.45 +/- 1.20)% yr(-1) and (-7.04 +/- 0.81)% yr(-1) for stratospheric HNO3 and HCl, respectively. The seasonal amplitudes of stratospheric HNO3 and HCl are 2.67 x 10(15) molec cm(-2) and 4.76 x 10(14) molec cm(-2) respectively, both reaching their maximum in March and their minimum in September, due to the tropopause height variation. Further, HNO3 and HCl data were used to compare with Microwave Limb Sounder (MLS) satellite data. MLS satellite data showed similar seasonal variations and annual rates with FTIR data, and the stratospheric HNO3 and HCl columns of the two datasets have correlation coefficients (r) of 0.87 and 0.88, respectively. The mean bias between satellite and FTIR data of stratospheric HNO3 and HCl columns are (-8.58 +/- 12.22)% and (4.58 +/- 13.09)%, respectively.