Mapping of Carbon gases through spectroscopic measurements of ground-Scattered sunlight (MapCScat)

• Applicant: Professor Dr. André Butz
• Subject Area: Atmospheric Science
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 449857152

Urban emissions of carbon dioxide (CO2) and methane (CH4) contribute largely to the global total greenhouse gas burden and thus, cities have been identified priority mitigation targets in terms of emission reduction. Guiding the mitigation measures and verifying their effectiveness, requires information on emission sources that is spatially and temporally resolved, complete, reliable and verified. Among the available greenhouse gas measurements, however, there is a gap of observations that have horizontal mapping capabilities on the scale of kilometers without requiring dense networks i.e. it needs a technique that fills the sensitivity gap between in-situ observations with local sensitivity and column-average remote sensing with area-integral sensitivity. Here, I propose to contribute to the improved understanding of urban greenhouse gas emissions by mapping urban CO2 and CH4 concentration fields using an innovative portable remote sensing observatory – thus filling the sensitivity gap. The main target region is Los Angeles where CO2 and CH4 emissions exceed 100 MtCO2/a and 300 ktCH4/a, respectively, making the larger Los Angeles area one of the emission hotspots of the world. Los Angeles is also one of the cities that is studied extensively with respect to collecting inventory information on its greenhouse gas emissions and verifying emission estimates through atmospheric concentration measurements. A pioneering experiment currently running at Los Angeles is the CLARS-FTS (California Laboratory for Atmospheric Remote Sensing - Fourier Transform Spectrometer) which is mounted on Mt. Wilson looking downward into the Los Angeles basin and collecting reflected sunlight. We have developed a portable variant of it and, together with local partners, we plan to co-deploy the portable and the stationary instruments during a field campaign in the Los Angeles area.The proposed research aims at validating the portable observatory and at exploring observation patterns such as zoom regions and crossed beam configurations in order to enhance the spatial and temporal resolution of the greenhouse gas maps. We further aim at developing an innovative radiative transfer and retrieval scheme that accounts for light scattering in the atmosphere and thus, enhances the accuracy of the technique. We will explore how well the observed variability and gradients in the CO2 and CH4 concentration fields fit to the information provided by emission inventories and how well we can disentangle local emission patterns from transport, regional in-/outflow, episodic events, and contributions of the urban biosphere.

• DFG Programme: Research Grants