Technical Support for the Acquisition of Water Vapour DIAL and Aerosol Measurements: Water Vapour Lidar Experiment WALEX 2005 Final Scientific Analysis Report

Kurzfassung

Design and performance studies for satellite missions measuring water vapour (e.g. WALES or SPACE-WAVES) require information on the real 2D structure of water vapour and aerosol/clouds in the troposphere, which can only be provided with sufficiently high spatial resolution and coverage by airborne water vapour lidar measurements. In this context the objective of WALEX 2005 is to extend the acquisition of representative lidar measurements of water vapour and aerosol/cloud properties to sub-Tropical and Tropical regions in the Indian Ocean and Micronesia, regions characterised by monsoon and intense inner tropical circulation. The opportunity to fly through these regions came with the EU-funded tropical campaign SCOUT-O3 (Stratospheric-Climate Links with Emphasis on the Upper Troposphere and Lower Stratosphere). The data provide unique illustrations of the mission concept showing a variety of meso-scale and synoptic scale structures in water vapour and aerosol/clouds. Nadir looking from the DLR-Falcon research aircraft, the profiles cover the troposphere between the flight level (10-11 km) and the ground if no dense cloud layers block the laser beam. The spectral and depolarisation information allows estimating the effective particle size and shape, i.e. the particles’ phase (water/ice). Large variability of H2O mixing ratio and particle distribution reflect the complexity of transport mechanisms near frontal zones, stratospheric filaments and other PV anomalies. Dry intrusions of upper tropospheric - lower stratospheric origin typically penetrate down to below 4 km altitude with H2O mixing ratios varying about more than an order of magnitude. ECMWF analyses are used to trace the origin of the observed air-mass structures and retrieve the responsible meso- and synoptic-scale dynamical processes. Implications for the impact on relatively coarsely resolved satellite measurements and the benefit of a space-borne H2O-DIAL are drawn.