GHG-KIT project: Inverse modelling of Vienna’s CH4 and CO2 emissions using in-situ and remote observations

The Austrian Flagship Project “GHG-KIT: Keep it traceable” aims to prototype an Austrian, Earth Observation-Integrated GHG measurement and modelling system, which can support national GHG emission monitoring. Among other aims, the project is working toward an Austrian inverse modelling framework to produce top-down estimates of national and subnational CO₂ and CH₄ fluxes that are independent of the current bottom-up system of the Austrian GHG inventory.
This conference contribution will present the GHG-KIT progress on inverse modelling of subnational CO₂ and CH₄ emissions, using Vienna as a case study. Vienna is the most populated city in Austria with around 2 million inhabitants, corresponding to slightly more than a fifth of the total Austrian population. To estimate the GHG emissions in Vienna the inversion framework FLEXINVERT is used. The atmospheric back trajectories for GHG measurements carried out in Vienna are calculated using the Lagrangian dispersion model FLEXPART-WRF, which is driven by WRF meteorology. The a priori fluxes of GHGs, used in FLEXINVERT, are prepared using WRF-GHG and are based on data from the Copernicus Atmosphere Monitoring Service (CAMS), among others. WRF-GHG is a Weather Research and Forecasting (WRF) model version that is coupled with chemistry modules as well as the GHG flux module and considers urban building features. Atmospheric ground-based observations of CO₂ and CH₄ mole fractions from the Vienna Urban Carbon Laboratory are included in the inverse modelling. These include in-situ observations from a tall-tower, as well as total column measurements at four locations from a 2022 summer campaign performed by the Technical University of Munich. Furthermore, the usability of satellite measurements over Vienna as an additional observation constraint will be investigated. This includes GHGSat measurements from Vienna that are carried out as part of the GHG-KIT project, as well as synthetic or possibly authentic observations from satellite missions (such as CO2M and MethaneSAT) that will be launched during the course of this project or shortly thereafter.