The airborne water vapor differential absorption lidar (DIAL) LEANDRE 2 system was developped at the Institut Pierre-Simon Laplace in the early nineties and is operational since 1995. It was designed to provide high resolution measurements of water vapor distribution in lower troposphere to improve current understanding of planetary boundary layer dynamics (including the entrainment process), surface-atmosphere moisture exchanges, aerosol-cloud-radiation interactions, convective initiation and maintenance, as well as cyclogenesis and severe storm formation.
LEANDRE 2 includes a tunable laser whose emission is positioned precisely upon an absorption line selected from two rotation-vibration bands in the near infrared (727-770 nm). This enables measurements in various humidity conditions, e.g. for integrated water contents ranging from 5 to 50 kg m-2. Seven absorption lines can be chosen from and changed in-flight, which is a unique feature among existing airborne DIAL systems.
As discussed in Bruneau et al. (2001), in which the measurements errors are analyzed, LEANDRE 2 characteristics permit water vapor mixing ratio measurements to be made with a precision better than 0.5 g kg-1 in the 0-5 km distance (from the aircraft) range and an along-beam resolution of 300 m. During COPS, LEANDRE 2 was flown onboard the SAFIRE F20 and was used in a nadir-pointing mode. The along track resolution is approximately 1 km and the vertical resolution appoximately 300 m.
The airborne lidar system LEANDRE 2 is described in
D. Bruneau, P. Quaglia, C. Flamant, M. Meissonnier and J. Pelon, 2001: The Airborne Lidar LEANDRE2 for Water Vapor Profiling in the Troposphere. Part I: Description. Appl. Opt., 40, 3450-3461.
D. Bruneau, P. Quaglia, C. Flamant and J. Pelon, 2001: The Airborne Lidar LEANDRE2 for Water Vapor Profiling in the Troposphere. Part II: First Results. Appl. Opt., 40, 3462-3475.