Oliver Lewis

Humidity is a crucial component of the atmospheric system. High resolution observations remain vital for accurate weather forecasting, yet retrieving data that captures the full spatial and temporal variability of humidity remains an enormously challenging task. We propose a new way of tackling this problem: interferometry of commercial aircraft radio transmissions. The air has a refractive index which depends on the temperature, pressure and humidity. By using interferometry (a form of direction finding) to measure how aircraft radio signals are deflected by the varying refractive index of the atmosphere, we can extract low-cost, high-volume humidity information. In this talk we describe the technique and show initial results using a prototype interferometer design. 

Irene Monreal Campos

Accurate quantification of methane emission fluxes from the oil and gas sector remains challenging. Previous methods can encounter issues associated with atmospheric boundary layer dynamics, and the presence of multiple overlapping emission sources.

We evaluate a methodology to estimate methane emission fluxes using the commercially available dispersion model ADMS6 in two different settings and airborne measurements. It takes into consideration many parameters including meteorology variables such as boundary layer stability and high-accuracy atmospheric dynamics measurements from the aircraft. Assumptions about the source type are needed for accurately simulating plume dispersion behaviour.

The first setting uses a single modelled plume concentration enhancements with a fixed mass flux input, and plume concentrations measured with the FAAM aircraft. The emission flux is scaled using the ratio between the modelled and observed enhancements.

For the second setting, we generate multiple modelled plumes with varying emission fluxes, creating different potential scenarios. By comparing these simulations to the observed plume, we identify the most accurate fit and extract the corresponding emission rate directly from the model inputs.

We then evaluate the methodologies using several emission case scenarios sampled by the FAAM Airborne Laboratory. The study focuses on offshore oil and gas extraction facilities such as the uncontrolled TOTAL ELGIN gas platform methane accidental release in 2012, and fugitive emissions from gas facilities on the Norwegian continental shelf.

The results from the methods are compared with the flux values determined with the more established mass-balance methodology and sources of uncertainties are discussed.

Liam Blyth

Methane (CH4) concentrations have been steadily increasing since pre-industrial times, contributing to approximately 35% of the overall heating observed during this period. While the primary drivers of long-term methane trends are well-established globally, uncertainties remain in understanding the year-to-year variability. This variability stems from the complex interplay of CH4 sources and sinks, compounded by their temporal variability. The hydroxyl radical (OH), a key species in the atmosphere and the primary sink for CH4, presents challenges due to its extremely short lifetime of approximately one second. To circumvent measurement difficulties, a proxy species, 14CO, is explored as a potential tracer within the UKESM1 model. Our extensive model study reveals a robust anti-correlation between 14CO and OH. Notably, the choice of measurement location emerges as a critical factor with polar region 14CO serving as an effective tracer for hemispheric OH, while tropical 14CO tracking OH concentrations within that region. Our investigation demonstrates the utility of 14CO in elucidating specific events, such as the drop in OH concentration observed in 1997/98, attributed to wildfires sparked by El-Nino. This insight contributes to a more comprehensive understanding of the excess CH4 growth recorded in that year.

An opportunity to ask questions of all the presenters, find out more and explore other ideas.