Harmonization of Mobile Methane Measurement Methods for IM4CA Project Based on a Controlled Release Experiment

The global concentration of methane (CH₄) in the atmosphere has more than doubled since the pre-industrial era and accounts for roughly one-third of current global warming. Because of its short lifetime, reducing anthropogenic CH₄ emissions can effectively lower its atmospheric levels and ease its climate impact. Accurately quantifying CH₄ emissions remains crucial for informing decision-making and mitigation strategies to lower those emissions.

One of the key objectives of the EU-funded research project IM⁴CA “Investigating Methane for Climate Actions” is to quantify the anthropogenic CH₄ emissions at the site level in Romania as a post-monitoring campaign following ROMEO campaign of MEMO2 Project. To achieve this, a variety of top-down CH₄ measurement approaches are to be implemented. These approaches use ambient CH₄ mole fraction measurements from sensors in vehicles, drones, aircrafts or tall towers combined with models to estimate total CH₄ flux rates at source of different scales. Intercomparing and harmonizing these CH₄ measurement methods are essential to accurately quantify CH₄ emissions in the context of a large-scale campaign.

Here, we aim to compare car and drone-based measurements prior to their field deployment in IM⁴CA, using a CH₄-controlled release experiment. This experiment was conducted around the Unmanned System Research Laboratory (USRL) airstrip in Orounda, Cyprus, where CH₄ was measured simultaneously using infrared spectrometers mounted on drone platforms and cars. To better account for any variability related to the measurement tools, three different drone systems were used, each equipped with one CH₄ gas analyzer, and three additional analyzers were mounted in the same car. The quantified CH₄ emissions using either mass balance or Gaussian plume model are compared from both measurement platforms and their possible joint use in the field for complete plume characterization is discussed.

The results from this experiment will enhance the accuracy of reported CH₄ fluxes and pave the way for harmonized measurement approaches, particularly for intensive large-scale monitoring campaigns within the IM⁴CA project and other similar third-party measurement initiatives.