Utrecht University (UU), overall lead and WP 4 lead, will perform, evaluate and interpret in situ methane isotope measurements at five European locations in PARIS. UU will oversee overall project management in WP 1. Two mobile instruments for high-precision isotope analysis of CH4 on ambient air are available for this purpose, complemented by a third instrument that can perform flask-based measurements in the UU laboratory. The infrastructure is embedded in a large atmospheric isotope laboratory at the Institute for Marine and Atmospheric Research Utrecht (IMAU) at Utrecht University with excellent technical support.

Wageningen University (WU) will perform inverse modelling of CO2 and APO data in WP 6. WU will also lead the reported emissions verification challenge activity and coordinate a protocol for the modelling exercise. WU has nearly two decades of experience in inverse modeling on global- and regional scale, and pioneered the Ensemble Kalman Filter technique for atmospheric CO2. This capacity has been used to simulate radiocarbon and APO on highresolution for Europe, to interpret measurements done in close collaboration with partner Groningen University (RUG). Infrastructure for observations and high resolution modelling in the Netherlands is consolidated through the national “Ruisdael Observatory for Atmospheric Science” which includes the Cabauw, Lutjewad, and Loobos towers, as well as our participation in the ICOS Carbon Portal.

University of Groningen (RUG) will perform continuous high-precision observations of O2 at the ICOS tall-tower Cabauw in the Netherlands in WP 6. RUG has access to critical infrastructure in this project, in the form of their own O2-analyzing system that has successfully been deployed in the Netherlands, and in Hyytiala Finland previously. The capacity to maintain and operate such an instrument is unique in the Netherlands, and only a few labs in the world (including PARIS partner UEA) currently can contribute such measurements. RUG’s Centre for Isotope Research (CIO) is part of the international community working on APO, and also part of the Dutch Ruisdael infrastructure project. In addition, RUG runs its own ICOS level-2 site Lutjewad in the Netherlands (also part of Ruisdael), which can serve as a back-up for Cabauw.