Pic du Midi Observatory, France (PDM)

Pic du Midi Observatory, France (PDM)


Lat : 42.9372°N, Lon : 0.1411°E, Alt : 2877 m above sea level

Sampling height: 10, 28 m above ground level


Pic du Midi is a high-altitude observatory for astronomy and atmospheric sciences on top of an isolated summit in the Pyrenees. The summit is situated well to the north of the Pyrenean main divide and thus forms a promontory over the French plain. This site is 150 km to the east of the Atlantic coast and thus most often exposed to oceanic westerlies or north-westerlies. However, advection of continental air from the Iberian Peninsula flowing over the Pyrenees is not rare.

In the context of the GEOmon programme, a study was conducted to characterize and compare the areas of influence (“footprints”) of various atmospheric background measurement sites in Europe (Henne et al., Atmospheric Chemistry and Physics, 2010). Pic du Midi (PDM) was categorized as “mostly remote” (as Sonnlick and Jungfraujoch in the Alps). Pic du Midi is located away from major urban or industrial areas. The population in radii of 10 and 50 km amount to about 13,000 and 412,000 inhabitants, respectively, concentrated in two main cities: Pau (217,000 inhabitants) and Tarbes (110,000 inhabitants), situated 55 km and 30 km away to the northwest, respectively. Outside of these two main cities, countryside and mountain areas are sparsely inhabited, with exception of the small town of Bagnères-de-Bigorre (9000 inhabitants) located 14 km north of PDM. Beyond ICOS measurements (carbon dioxide, methane, carbon monoxide, water vapor), permanent monitoring of other gaseous species (ozone, carbon monoxide, mercury), aerosol particles and meteorology is also being performed at PDM.

Measured species

In situ and continuous: CO2, CH4, CO and 222Rn

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


F. Gheusi, M. Lopez, M. Ramonet


Site Web

Observatoire du Pic du Midi

Relevant publications

El yazidi, A., M. Ramonet, P. Ciais, G. Broquet, I. Pison, A. Abbaris, D. Brunner, S. Conil, M. Delmotte, F. Gheusi, F. Guerin, L. Hazan, N. Kachroudi, G. Kouvarakis, N. Mihalopoulos, L. Rivier, and D. Serça (2018), Identification of spikes associated with local sources in continuous time series of atmospheric CO, CO2 and CH4, Atmospheric Measurement Techniques, 11(3), 1599-1614, https://doi.org/10.5194/amt-11-1599-2018.

Hulin, M., F. Gheusi, M. Lothon, V. Pont, F. Lohou, M. Ramonet, M. Delmotte, S. Derrien, G. Athier, Y. Meyerfeld, Y. Bezombes, P. Augustin, and F. Ravetta (2019), Observations of Thermally Driven Circulations in the Pyrenees: Comparison of Detection Methods and Impact on Atmospheric Composition Measured at a Mountaintop, Journal of Applied Meteorology and Climatology, 58(4), 717-740, doi:10.1175/jamc-d-17-0268.1.

Fu, X. W., N. Marusczak, X. Wang, F. Gheusi, and J. E. Sonke (2016), Isotopic Composition of Gaseous Elemental Mercury in the Free Troposphere of the Pic du Midi Observatory, France, Environmental Science & Technology, 50(11), 5641-5650, https://doi.org/10.1021/acs.est.6b00033

Marenco, A., H. Gouget, P. Nédélec, J.-P. Pagés, and F. Karcher (1994), Evidence of a long-term increase in tropospheric ozone from Pic du Midi data series: Consequences: Positive radiative forcing, JGR, 99(D8), 16617-16632, https://doi.org/10.1029/94JD00021.