Abstract

Abstract: Through injection of gas phase chemicals such as greenhouse gases (GHGs) and pollutants, the composition of the Earth’s atmosphere is changing, affecting radiative, chemical, and transport processes within the atmosphere, and the health of bio-receptors and ecosystems. Understanding natural and anthropogenic processes leading to gas emissions requires quantitative observations at the scale of the emitting unit, with a temporal and spatial resolutions allowing to resolve dynamic emission behaviours and their spatial patterns. In the case of anthropogenic GHG emissions from the energy, the waste management, or the agricultural sectors, spatio-temporal quantification of gas emitted at the facility scale is also critical to the implementation of sustainable climate policies, such as the Net Zero agenda, to allow for fair and transparent reporting, monitoring and verification. Considering methane, great progress has been made towards improved quantitative emission monitoring to reconcile bottom-up emission inventories and top-down estimates. Novel measurement systems, particularly satellite-borne ones, now provides global coverage when the cloud cover allows, and can ‘focus’ on large facilities to provide snapshot quantitative estimates. However, this way only fairly large emissions can be measured (~100kg/h), and a snapshot measurement does not provide the temporal patterns of emissions often associated to facility operations. Satellite-borne measurements also need robust ground-based validation to demonstrate their data quality.

In this context, the need for continuous gas emission monitoring systems capable of characterising the emitting behaviour of an entire facility, in space and time, remains acute. To address the need, we have developed the concept of gas emission laser tomography made of 1) high-resolution spectroscopic measurements of atmospheric transmission over multiple open-paths, and 2) a inversion scheme to reconstruct, from the time series of multi-path integrated concentrations, the evolution of three dimensional gas plumes and associated emission sources. Field deployments at oil and gas, waste treatment, and agricultural facilities, together with controlled gas released tests, have established the highly promising capabilities of gas emission laser tomography for methane characterisation. We will describe the system, present some example of deployments and results, and discuss the current developments to additional trace gases, as well as improvements of the inversion framework based on Bayesian state estimation.

Biography: Damien Weidmann heads the Spectroscopy programme of the Space Science and Technology Department of the STFC Rutherford Appleton Laboratory (aka RAL Space). He has been conducting research and development for more than 30 years in molecular spectroscopy and atmospheric sensing, in France, the USA and the UK. He has a particular interest in the development and application of novel high resolution chemical sensing concepts enabled by spectroscopy, covering technologies, algorithms, systems, and mission concepts. DW is also co-founder and chief scientific officer of MIRICO Ltd, a company exploiting high-precision gas sensing for terrestrial applications.