On the usefulness of an airborne lidar for O3 layer analysis in the free troposphere and the planetary boundary layer

Abstract

Ozone vertical profiling with a lidar is well adapted to the spatial and temporal O₃ variability analysis either in the free troposphere, when studying the respective impact of chemical production and dynamical processes, or in the planetary boundary layer (PBL) when characterizing the diurnal evolution of ozone plumes during pollution episodes. Comparisons with other measuring techniques (ozonesonde and aircraft in-situ measurements) demonstrate the lidar ability to characterize narrow layers (< 500 m) with a good accuracy (δO₃ < 5–10 ppb). Application of airborne or ground-based operation of the CNRS airborne ozone lidar show its ability (i) to observe O₃ layering above the PBL during two field experiments held to study air pollution in the Po Valley, Northern Italy, and the city of Marseille, Southern France, (ii) to improve airborne campaign planning (real time information on position of O₃ layers) and analysis (three-dimensional perspective for layers detected by in-situ measurements) when chemical characterization of narrow O₃ layers in the free troposphere is sought, (iii) to map O₃ inhomogeneity down to an horizontal scale of 10–20 km within or above the polluted PBL by airborne measurements. For O₃ pollution studies, understanding the origin and the life cycle of O₃ layering is the first priority, and in this case the optimum use of the lidar remains the continuous operation of a ground-based instrument.