Suchergebnisse

Satellites that measure the chemical composition of the atmosphere are becoming more accurate and numerous, providing a unique opportunity to independently monitor emissions for large geographical regions in a consistent way. This report elaborates the development of a software tool which is able to process satellite observation data and estimate NOx emissions from it for a pre-defined area. The tool is fully operational for processing satellite observations from the TROPOspheric Monitoring Instrument (TROPOMI) and the Ozone Monitoring Instrument (OMI). The tool is modular in design with the capability in mind to digest satellite data from various satellites and for pollutants. It is furthermore designed to be relatively simple and operates without a dependence on complicated and computationally demanding atmospheric models. The methods for satellite based emission estimation can complement data from emission inventories by incorporating independent measurement techniques into the reporting scheme. This would help to identify room for improvement in the compilation of inventories as well as boost the transparency and confidence in the reported data. The developed capabilities of the tool are applied to derive German national emissions for the year 2019 as well as the trend in NOx emissions between 2005 and 2019. Three methods to derive NOx emissions estimates from satellite observations are developed and applied to TROPOMI data for the year 2019. Derivation of emissions through direct integration of atmospheric concentrations over the vertical columns within a region (called the Naïve method) results in an estimate of German NOx emission of 1097.1 kton. A Gaussian plume-based fitting routine (Fioletov et al., 2017) led to an estimated 1241.0 kton and a computation based on the divergence of the pollutant flux field (Beirle et al., 2019) resulted in an estimate of 1260.7 kton. All three estimates are within 15% of the reported total emissions for 2019 (1108.82, NFR, Submission 2022 (europa.eu)). To derive the trend in NOx emissions within the past 15 years, the Fioletov method was applied to OMI observations between 2005 and 2019, showing an average decrease of around 25% between the 2005-2007 and 2017-2019 period, which is in agreement with the reduction reported in emission inventories (20% reduction between 2005-2007 and 2014-2016 period and 23% between 2005-2007 and 2017-2019 period found in the 2022 NFR reported totals based on fuel sold [Submission 2022]). TROPOMI was launched in October 2017 hence its data cannot be used to monitor long term trends. While all three methods show comparable results for 2019 at country level, differences were observed at smaller administrative scales, notably the Naïve method not being able to reproduce local emission gradients to the same level as the other methods. At the highest administrative level (Districts) the Gaussian plume method starts to outperform the divergence method. Both methods can be further improved to reach higher levels of accuracy. The majority of the uncertainties relate to the estimated NOx lifetime in the calculations and inaccuracies in the TROPOMI-NO2 product. An important issue when comparing emission estimates from satellite observations with the official inventory data is the fact that the inventories (by convention) do not include all emission sources which contribute to the observed concentrations. Adding estimates for natural emissions and emissions from the so called "Memo" items 1 from the IIR to the national total as reported in the IIR bring the inventory data and the satellite observation closer together.