Spectral measurement show that solar radiation can contain the information on extremely high near-surface concentrations of the hydrochloric acid vapor that leads to impossibility of estimation of its general content using the background a priori information. The alternative representation of a priori information is proposed that allows the number of retrieved values of hydrochloric acid vapor be increased by 10%. The existence of high near-surface concentrations of the gas is confirmed by the received results of the processing of spectral data. The good agreement between estimates of stratospheric contents of the hydrochloric acid vapor retrieved from ground-based measurements using the proposed a priori information and independent satellite data is shown: mean differences between data received by two methods are 4.4%, the standard deviation of the differences is 5.7%, and the correlation coefficient is 0.85.