Ground-based installations at the Haute Provence Observatory (OHP) to monitoring and study condensation trails

Cloud formation can also result from human activity, such as aircraft condensation trails, or contrails. They are created by the release of water vapor and soot from aircraft. Contrails can then change shape rapidly after forming, and then persist in the atmosphere for varying lengths of time. They will persist in the atmosphere if the air is super-saturated with ice, i.e. when the height of aircraft is in the upper troposphere. They can then evolve into cirrus clouds if the thermodynamic conditions of the atmosphere are favourable. These cloud-like contrails will therefore have environmental consequences that need to be understood to be included in climate models as non-CO2 contributions. These are the main motivations that led us to the establishment of ground facilities at the Haute Provence Observatory (OHP south of France) to observe and study condensation trails. They are mainly composed of a Lidar, radiosondes and two sets of fisheye cameras recording hemispherical images of the sky in the visible and thermal infrared for nighttime observations. The Global Horizontal Irradiance (GHI) of the Sun and some meteorological data on ground are also recorded together with the images. We will first describe in detail the instrumentation currently installed on the ground and operational for contrail monitoring. We will then present a case of a contrail recorded on March 21, 2024 at OHP and detail all the processing steps, from its detection to its analysis, including the identification of the aircraft trajectory in the images and the expansion of the contrail it leaves.