The Facility Level and Area Methane Emissions inventory for the Greater Toronto Area (FLAME-GTA)

We present the Facility Level and Area Methane (CH4) Emissions inventory for the Greater Toronto Area (FLAME-GTA). We estimate that total emissions of CH4 in the GTA, the most populous metropolitan area in Canada, are about 86 ? 38 Gg/yr. The FLAME-GTA estimate is within uncertainty of, but lower in magnitude than the existing gridded inventories provided by the Emissions Database for Global Atmospheric Research (EDGAR v 5.0), and by Environment and Climate Change Canada?s Air Quality Research Division (ECCC - AQRD) that estimate emissions of 96 ? 48 Gg/yr and 143 ? 71 Gg/yr in the GTA region, respectively. Using a Lagrangian transport model, we predict atmospheric mixing ratios based on different emission inventories and compare the predictions with in situ measurements available from an observatory within the GTA for January?March in both 2015 and 2016. Due to the strong influence of local sources on our observations only a subregion of our GTA inventory is evaluated. These results identify the need for a more extensive measurement network and an improved atmospheric transport modeling effort for further evaluation of the emission inventories.

Automated summary

The study presents the Facility Level and Area Methane (CH4) Emissions inventory for the Greater Toronto Area (FLAME-GTA), estimating total emissions of CH4 to be about 86 ± 38 Gg/yr. Using a Lagrangian transport model, atmospheric mixing ratios based on different emission inventories are predicted and compared with in situ measurements. Results indicate the need for a more extensive measurement network and an improved atmospheric transport modeling effort for further evaluation of emission inventories.