Saclay Observatory, France (SAC)

Saclay Observatory, France (SAC)


CEA – Saclay, 91191 Gif-sur-Yvette, FRANCE
Lat: 48.72°N, Lon: 2.14°E, Alt: 160 m above see level
Sampling heights: 15, 60, 100 m above ground level


The Saclay station is a semi-urban site surrounded by agricultural fields (47%), forests (25.0%), and urban residential areas (22%). The site is located ~20 km south-west of the Paris center on the Plateau de Saclay. The closest village and small town are Saint-Aubin (673 inhabitants) and Gif-sur-Yvette (21,352 inhabitants), located 500 m north-west and 1 km south of the station, respectively. There is a high traffic road (N118) during the rush hours located 1km from the tower.

The dominant wind direction is south-west (35% of the time), with a wind speed between 5 and 10 m.s-1. Only 14% of the time during most of the year, but 35% of the time in spring, the wind comes from Paris (north-east direction), transporting polluted air masses.

The Saclay station is associated to SIRTA observatory which is part of ACTRIS and GRUAN. The aerosol and chemical species measurements are performed at a site 2 km away from the Saclay tall tower, whereas continuous planetary boundary layer height measurements using lidar and radar systems, are performed at another site 5km away.

Measured species

In situ and continuous : CO2, CH4, N2O, CO and 222Rn
Integrated: 14CO2 (over 15 days)

Flasks : CO2, CH4, CO, N2O, SF6, H2, 14CO2, 13CO2

Meteorological parameters : Temperature, relative humidity, atmospheric pressure, wind speed and direction


M. Lopez, M. Ramonet


Relevant publications

Grossi, C., S. Chambers, O. Llido, F. Vogel, V. Kazan, A. Capuana, S. Werczynski, R. Curcoll, M. Delmotte, A. Vargas, J.-A. Morguí, I. Levin, and M. Ramonet (2020), Intercomparison study of atmospheric 222Rn and 222Rn progeny monitors, Atmospheric Measurement Techniques, 13(5), 2241-2255,

Lian, J., F.-M. Bréon, G. Broquet, T. Lauvaux, B. Zheng, M. Ramonet, I. Xueref-Remy, S. Kotthaus, M. Haeffelin, and P. Ciais (2021), Sensitivity to the sources of uncertainties in the modeling of atmospheric CO2 concentration within and in the vicinity of Paris, Atmospheric Chemistry and Physics, 21(13), 10707-10726,

Nalini, K., T. Lauvaux, C. Abdallah, J. Lian, P. Ciais, H. Utard, O. Laurent, and M. Ramonet (2022), High-Resolution Lagrangian Inverse Modeling of CO2 Emissions Over the Paris Region During the First 2020 Lockdown Period, Journal of Geophysical Research: Atmospheres, 127(14), e2021JD036032, doi:

Xueref-Remy, I., E. Dieudonné, C. Vuillemin, M. Lopez, C. Lac, M. Schmidt, M. Delmotte, F. Chevallier, F. Ravetta, O. Perrussel, P. Ciais, F.-M. Breon, G. Broquet, M. Ramonet, T. Gerard Spain, and C. Ampe (2018), Diurnal, synoptic and seasonal variability of atmospheric CO2 in the Paris megacity area, Atmospheric Chemistry and Physics, 18(5), 3335-3362,