Airborne water vapour and wind lidar measurements of latent heat fluxes during COPS 2007

Abstract

During the Convective and Orographically-induced Precipitation Study (COPS) in July 2007 over the Black Forest Mountains in south-western Germany, tropospheric profiles of water vapour and wind were measured with a differential absorption lidar (DIAL) and a heterodyne detection 2-μm Doppler wind lidar collocated on board the DLR Falcon research aircraft. The DIAL “WALES” is a newly developed four-wavelength system operating on three water vapour absorption lines of different strengths, one offline wavelength at 935 nm (each 50 Hz, 40 mJ), and 532 and 1064 nm for aerosol profiling. It is designed as an airborne demonstrator for a possible future spaceborne water vapour lidar mission. For the study of summertime convection initiation over complex terrain, latent heat flux missions were flown where both lidars were pointed nadir-viewing. Using eddy-correlation of the wind and water vapor fluctuations beneath the aircraft, an area-representative water vapor or latent heat flux profile can be obtained by a single over-flight of the convective boundary layer in complex terrain. The lidars’ horizontal and vertical resolution is about 200 m which resolves the dominant circulation patterns and flux contributions. This novel instrumentation allows obtaining profiles of the latent heat flux beneath the aircraft from one single over-flight of the area of interest.