Water Vapour and Wind Profiles from Collocated Airborne Lidars during COPS 2007

摘要

Tropospheric profiles of water vapour and wind were measured with differential absorption lidar (DIAL) and heterodyne detection wind lidar collocated onboard the DLR Falcon research aircraft during the Convective and Orographically-induced Precipitation Study (COPS; www.cops2007.de) over Southwest Germany in summer 2007. This international field campaign aimed at refining observational and modelling efforts to improve the forecast skill of convective precipitation over complex terrain in the summer season. The DIAL, a completely new system with four wavelengths (each 50 Hz, 40 mJ) at 935 nm, was installed nadir-viewing. The 2-micron wind lidar was operated either in scanning mode at 20 degrees off-nadir for 3d-wind profiles or in nadir-viewing mode for high resolution vertical wind measurements. The unique combination of both lidars enables the measurement of both horizontal (humidity advection) and vertical (latent heat) fluxes of water vapour that play an eminent role in precipitation forecast and convection initiation. The wind lidar's spatial resolution is 100 m in the vertical and 150 m (vertical wind, boundary layer) to 12 km (3d-wind profiles, whole troposphere) in the horizontal. The DIAL horizontal and vertical resolution ranges from 150 m in the boundary layer to 500 m in the upper troposphere. This high spatial resolution permits the investigation of small-scale processes such as turbulent humidity transport in the convective boundary layer or orographically-induced flow perturbations. Likewise, meso- and synoptic scale processes, e.g. upper level potential vorticity streamers were sampled by flying extended legs across Western Europe.