Latent heat flux measurements over complex terrain by airborne water vapour and wind lidars
✍ Scribed by Christoph Kiemle; Martin Wirth; Andreas Fix; Stephan Rahm; Ulrich Corsmeier; Paolo Di Girolamo
- Publisher
- John Wiley and Sons
- Year
- 2011
- Tongue
- English
- Weight
- 580 KB
- Volume
- 137
- Category
- Article
- ISSN
- 0035-9009
- DOI
- 10.1002/qj.757
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✦ Synopsis
Abstract
Vertical profiles of the latent heat flux in a convective boundary layer (CBL) are obtained for the first time over complex terrain with airborne water vapour differential absorption lidar and Doppler wind lidar. During the Convective and Orographically‐induced Precipitation Study (COPS) over the Black Forest mountains in south‐western Germany both lidars were installed nadir‐viewing onboard the Falcon research aircraft of the Deutsches Zentrum für Luft‐ und Raumfahrt (DLR). On 30 July 2007, additional in situ measurements by the Karlsruhe Institute of Technology (KIT) were performed with a Dornier‐128 aircraft that flew below the Falcon. This unique instrument configuration allows us to validate the lidar‐derived fluxes and to assess lidar‐specific issues such as instrument noise and data gaps that impinge on the results. The cospectra of in situ humidity and vertical velocity peak at wavelengths between 1 and 3 km and reveal that the dominant scales of turbulent transport are larger than 700 m in dimension. Consequently the airborne lidars' horizontal and vertical resolution of ∼ 200 m is sufficient to capture most of the flux. The lidar and in situ fluxes of five collocated 45 km flight legs agree within ±20%; the average difference over the total distance of 225 km is 3%. A flux comparison with ground‐based water vapour Raman and wind lidars shows agreement within the instruments' accuracies under low‐wind conditions. All latent heat fluxes vary between 100 and 500 W/m^2^ in the CBL and have small vertical divergences. Vertical velocity spectra in the mid‐CBL enable us to estimate the dissipation rate of turbulent kinetic energy that amounts to 5 × 10^−4^ m^2^ s^−3^ in the Rhine Valley and 10^−3^ m^2^ s^−3^ over the Black Forest mountains. This new airborne lidar instrumentation proves to be a valuable tool for the study of CBL processes and variability, particularly over complex terrain. Copyright © 2011 Royal Meteorological Society