Technique for Inverting Transmission Spectra to Measure Freon Concentration

Abstract

We propose an approach to selecting the optimal parameters for solving the inverse problem for determining the total freon content (TC) from ground-based spectrometric measurements of solar radiation. The approach was developed for measurements at the St. Petersburg NDACC station using a Bruker FS125HR Fourier-transform interferometer and implemented as applied to measurements of the total content of the hydrochlorofluorocarbon R-22 (HCF 2 Cl). Based on the optimal set of parameters obtained, we retrieved the total R-22 content above the St. Petersburg station in the period 2009–2018 and obtained estimates of the measurement uncertainties: average systematic uncertainty 4.8%, random uncertainty 3.7% over the entire observational period. A preliminary estimate of the trend is 2.64 ± 0.22% per year.