Evaluating the Top-down Emission Rate Retrieval Algorithm (TERRA) Using Virtual Aircraft-based Sampling Within the GEM-MACH Model

Between August 13th and September 7th of 2013, aircraft-based measurements of air pollutants were collected in support of the Joint Canada-Alberta Implementation Plan on Oil Sands Monitoring (JOSM). The Top-down Emission Rate Retrieval Algorithm (TERRA) was developed by Environment and Climate Change Canada (ECCC) to estimate facility emission rates based on the aircraft measurements. Here, as part of a larger effort on TERRA improvement, ECCC's air quality model, Global Environmental Multiscale-Modeling Air-quality and CHemistry (GEM-MACH), was used as a surrogate source of concentration and meteorology data. The TERRA-calculated emission rates are compared with those input into GEM-MACH, for different TERRA configurations. This work evaluates the combination of TERRA and GEM-MACH as a proxy for testing the downward extrapolation schemes within TERRA and identifies possible avenues for GEM-MACH and/or TERRA improvements. Outcomes from this work can provide useful suggestions for future flight plans for top-down emission rate estimations.