A video abstract for "A bottom-up emission estimate for the 2022 Nord-Stream gas leak: derivation, simulations and evaluation" to be submitted to Atmospheric Chemistry and Physics. The manuscript abstract: A major release of methane from the Nord Stream pipelines occurred in the Baltic sea on 26 of September 2022. Elevated levels of methane were recorded at many observational sites in northern Europe. Based on information from public media, numerical simulations have been performed reconstructing vertical profiles and temporal evolution of the methane releases from the broken pipes with subsequent transport in the atmosphere. The emission rates were calculated with a numerical solution to a problem of a gas leak from a half-opened pressurized pipe. Vertical distribution of the release was based on a parametrization for an injection height of buoyant plumes (e.g., fire plumes). The estimated rates were used to simulate the dispersion of the gas cloud with the SILAM chemistry transport model. The simulated fields of the excess methane led to noticeable increase of concentrations at several carbon-monitoring stations in the Baltic Sea region. Comparison of the simulated and observed time series indicated a good agreement between timing of the plume arrival/departure at the stations with observed methane peaks. Comparison of absolute levels was quite uncertain because the magnitude of the observed and modelled peaks was comparable with natural variability of methane concentrations. The obtained emission inventory and the simulation results can be used for further analysis of the incident and its climate impact. It can also be used as a test case for atmospheric dispersion models. |