Performance Simulations of Spaceborne Methane Observations by Integrated-Path Differential Absorption Lidar

Kurzfassung

A lidar-based satellite instrument for global observations of atmospheric methane is foreseen whose expected performance and technical feasibility are currently investigated in planning phase 0/A. Methane is, after carbon dioxide, the second most important greenhouse gas, whereby its anthropogenic emissions are much more uncertain. In addition, climate change may cause an important positive feedback of yet unknown intensity by release of methane from melting permafrost soils and ocean sediments. The current observational network is not able to monitor these sources with sufficient density and accuracy: While the ground-based in-situ network is too sparse, existing passive remote sensors on spacecraft are not accurate enough. Preliminary studies show that lidar with a realistic instrument design on a LEO platform has the potential to overcome these shortcomings and to measure methane with an accuracy and spatial resolution that satisfies the requirements of the user community. The presentation will include basic issues such as the selection of suitable methane absorption wavelengths, key performance parameters of instrument and spacecraft, and an assessment of the residual bias. It will highlight critical performance parameters such as instrument noise and surface reflectivity, and list the instrument and platform characteristics needed to fulfil the user requirements.