GEMINI-UK: a new UK network of ground-based greenhouse gas observing spectrometers to help track progress towards net-zero targets

As part of the UK Greenhouse gas Emissions Measurement Modelling Advancement programme, the National Centre for Earth Observation are establishing the Greenhouse gas Emissions Monitoring network to Inform Net-zero Initiatives for the UK (GEMINI-UK). The primary aim of the GEMINI-UK network, comprising ten Bruker EM27/SUN shortwave infrared spectrometers, is to help quantify regional net GHG emissions across the UK, complementing in situ measurements collected by the existing tall tower network. Collectively, these data will eventually form the backbone of a pre-operational GHG emissions monitoring framework. The GEMINI-UK instruments observe column concentrations of carbon dioxide, methane, and carbon monoxide in cloud-free conditions, which we are using in the context of Bayesian inverse methods to constrain regional flux estimates of these gases. We have designed the measurement network to deliver the biggest error reductions in carbon dioxide flux estimates, working closely with host partners that include UK universities and schools and NERC facilities to promote the open access and transparency of the collected data. Continuous and autonomous operation of these instruments at each site is achieved by an automated weatherproof enclosure, based on a design developed by University of Edinburgh researchers, which previously enabled year-round measurements to be collected during the UK DARE-UK experiment in central London. In this presentation we describe the status and longer-term goals of GEMINI-UK, which is coming online through the first half of 2024, including an ongoing evaluation of EM27/SUN with a higher specification TCCON spectrometer at Harwell. We will also report data from the DARE-UK London deployment, which demonstrates the value in using all-weather enclosures and allows comparison with coincident measurements collected by the NASA OCO-2 and OCO-3 Earth orbiting instruments.