After two and a half months in the USA, scientists of the DLR Institute of Atmospheric Physics have returned to Oberpfaffenhofen. They took part at the aircraft measurement campaign ACT-America (Atmospheric Carbon and Transport), which was led by the Pennsylvania State University (Prof. Dr. Kenneth J. Davis) and NASA, to investigate greenhouse gas emissions and -transport.
Anthropogenic emissions of greenhouse gases like carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) are causing a constant warming of our planet since the industrialization. Despite a lot of efforts and advances, there are still gaps in knowledge regarding sources, sinks and transport of anthropogenic greenhouse gases. However, a detailed understanding of all these processes and their interactions is a fundamental requirement to derive effective steps to mitigate global warming. In this context, an exact knowledge about the actual condition of the atmosphere is essential. The goal of ACT-America is to close these gaps of knowledge in the “hotspot-area” USA, the second largest CO2 emitter worldwide (status 2014).
Within the scope of ACT-America, within six weeks 18 scientific flights with the NASA-C130 and also with the NASA-B200 were conducted in the middle and lower troposphere. During this time, the team was stationed for two weeks in Virginia, Louisiana, and Nebraska, respectively, which enabled the coverage of three big regions in the USA: The Atlantic coast, the gulf coast, and the Midwest. Thus, in the course of the campaign 200 hours of data were collected.
The employed in-situ and Lidar instruments measured dry air mixing ratios and column concentrations of the three most important greenhouse gases, CO2, CH4, and N2O. The DLR-IPA operated a novel in-situ absorption spectrometer (QCLS: Quantum Cascade Laser Spectrometer) which measures, besides these three greenhouse gases, also H2O, C2H6, and CO.
In the next months, the DLR scientists process and analyze the collected data. In collaboration with the American colleagues emission sources of CH4 and N2O in the investigated regions are then quantified with the help of model simulations, to minimize uncertainties in the emission estimations for climate simulations. Furthermore, the transport of greenhouse gases by mesoscale weather systems (e.g. cold fronts) is determined. Last but not least, the data is used to validate the CO2 measuring satellite OCO-2 (Orbiting Carbon Observatory-2).
ACT-America team in front of the NASA-B200 and the NASA-C130 (Photo: D.C. Bowman, NASA Langley, CC-BY 3.0)
View from the NASA-C130 during a flight over Nebraska (Photo: M. Smithers, CC-BY 3.0)