Total Column Mixing Ratios of Carbon Dioxide, Methane and Carbon Monoxide from Toronto (UTSC)

These data are retrievals of column-average dry-air mole fractions of CO2, CH4, CO, and H2O (referred to as xco2, xch4, xco, xh2o) collected using a Bruker Optics EM27/SUN Fourier Transform Spectrometer (FTS) at the University of Toronto Scarborough Campus (UTSC; 43.784 N, 79.188 W). This is one of five sites in the Greater Toronto Area as part of long-term monitoring. The data were processed using GGG2020, which is also used by the Total Carbon Column Observing Network (TCCON). The retrieval algorithm uses a scaling profile retrieval in which a prior estimate of the atmospheric profile of trace gas concentrations is derived from a model. The relative concentrations between atmospheric layers (i.e., the profile shape) in the prior remains fixed and least squares methods are used to calculate a scaling factor for this profile that optimizes the fit to the measured spectra. The resulting scaled profile is then integrated to yield a total column-average dry-air mole fraction (more details in doi: 10.14291/tccon.ggg2014.documentation.R0/1221662). Quality filtering and post-processing methods are described by Mostafavi Pak et al., 2023 (doi: 10.5194/amt-16-1239-2023). In post-processing, an airmass dependent bias correction is applied, followed by an additive bias correction to bring all the EM27 instruments into agreement with a standard reference instrument, and finally a scaling factor is applied to correct to the WMO scale based on comparisons to AirCore measurements. Because of their geographic proximity, the retrievals for the four Toronto sites, excluding the remote northern site at CARE (see doi for sites below), used common prior profiles based on model data interpolated to 43.63N, 79.38W. This was done to minimize the impacts of using different priors when analyzing gradients across the city of Toronto, but the CARE site is too far from the other sites for this to be reasonably applied.
Note that these are the observations collected with the instrument identified as "tb" and owned by the University of Toronto. Observations were continued at UTSC with an instrument owned by Environment and Climate Change Canada, and those data are published separately under doi: TBD.

Sites and data availability:
University of Toronto St. George (UTSG; 43.661 N, 79.399 W) doi: 10.5683/SP3/WMQFDC.
Environment and Climate Change Canada, Downsview (DOW; 43.781 N, 79.468 W) doi: 10.18164/f34f7044-0317-4774-a528-c60e84973f91.
University of Toronto Scarborough (UTSC; 43.784 N, 79.188 W) doi: 10.5683/SP3/80TERS.
University of Toronto Mississauga (UTM; 43.549 N, 79.662 W) doi: 10.18164/f34f7044-0317-4774-a528-c60e84973f91.
Centre for Atmospheric Research Experiments (CARE; 44.231 N, 79.783 W) doi: 10.18164/f34f7044-0317-4774-a528-c60e84973f91.