NDACC FTIR trace gas measurements at the University of Toronto Atmospheric Observatory from 2002 to 2020

Abstract. Nineteen years of atmospheric composition measurements made at the University of Toronto Atmospheric Observatory (TAO, 43.66° N, 79.40° W, 174 m.a.s.l.) are presented. These are retrieved from Fourier Transform InfraRed (FTIR) solar absorption spectra recorded with an ABB Bomem DA8 spectrometer from May 2002 to December 2020. The retrievals have been optimized for fourteen species: O₃, HCl, HF, HNO₃, CH₄, C₂H₆, CO, HCN, N₂O, C₂H₂, H₂CO, CH₃OH, HCOOH and NH₃ using the SFIT4 algorithm. The measurements have been archived in the Network for Detection of Atmospheric Composition Change (NDACC) data repository in Hierarchical Data Format version 4 (HDF4) files following the Generic Earth Observation Metadata Standard (GEOMS) and are also publicly available on Borealis, the Canadian Dataverse Repository. In this paper, we describe the instrumentation, the retrieval strategy, the vertical sensitivity of the retrievals, the quality assurance process, and error analysis of the TAO FTIR measurements, and present the current version of the time series.