Retrieval of vertical profiles of ozone from high-resolution infrared solar spectra at Rikubetsu, Japan

Abstract

Vertical profiles of volume mixing ratios (VMRs) of O3 were retrieved from high-resolution, infrared solar absorption spectra taken at Rikubetsu, Japan (43.5°N), by a ground-based Fourier transform infrared spectrometer (FTIR). The VMR profile retrieval is based on an iterative inversion algorithm, which utilizes line-by-line, layer-by-layer calculations. Two different microwindow regions (1146 and 1163 cm-1) were used for the retrieval calculations. Eighty ozone vertical profiles were retrieved from the two spectral regions from 40 spectra and were compared with 17 ozonesonde measurements from a nearby station. Average differences between 18 and 34 km were less than ±12% for both 1146 and 1163 cm-1 retrievals. The standard deviation of the average differences between 18 and 34 km were less than 19% and 14% for respective windows. Effects of several different factors on errors of profile retrievals, such as initial guess, temperature profiles, and instrument line shape functions, were evaluated by numerical simulation. The estimated errors were extremely consistent with the observed errors between 18 and 34 km, suggesting that the FTIK was optically well adjusted. In general, retrieval of the O3 profile gives VMRs in an accuracy better than 40% at 14 km, improving to 10-15% between 18 and 30 km, with precision of 30% and 20% for these altitude ranges, respectively.