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====== Profiles of the Turbulent Humidity Flux: from measurement to water budget ======


Jan H. Schween\\
Paolo di Girolamo\\

Advances in lidar technology allowed in the last years the development of robust Doppler lidars as well as Raman Lidars for profiling of the humidity content of the atmosphere above.  Combining both kinds instruments should allow to calculate fluxes. We present data from the combination of a commercial available Doppler Lidar (HALO photonics, GB) and the University of BASILicata UV Raman lidar system (BASIL) research instrument. 

Following the principles of Reynolds averaging, the turbulent flux is the covariance between vertical wind speed and humidity. It is thus a statistical quantity describing the state of the atmosphere in a limited time interval. Several sources of uncertainty are investigated, starting from the inherent noise in lidar data, separation of the sensors (including a correction for this) and the limited sampling volume. Techniques commonly applied to surface data are used to estimate the optimal averaging length. The resulting fluxes are used for a budget estimate considering the turbulent flux at the surface, detrainment into the free troposphere at the top of the boundary layer and horizontal advection.