ORIGINAL PAPER Wind fields in heterogeneous conifer canopies: parameterisation of momentum absorption using high-resolution 3D vegetation scans Ronald Queck • Anne Bienert • Hans-Gerd Maas • Stefan Harmansa • Valeri Goldberg • Christian Bernhofer Received: 14 June 2010 / Revised: 13 May 2011 / Accepted: 12 July 2011 / Published online: 4 August 2011 Ó Springer-Verlag 2011 Abstract Applications of flow models to tall plant can- opies are limited, amongst other factors, by the lack of detailed information on vegetation structure. A method is presented to record 3D vegetation structure and make this information applicable to the derivation of turbulence parameters suitable for flow models. The relationship between wind speed, drag coefficient (C D ) and plant area density (PAD) was experimentally investigated in a mixed conifer forest in the lower part of the Eastern Ore Moun- tains. Essential information was gathered by collecting multi-level high-frequency wind velocity measurements and a dense 3D representation of the forest was obtained from terrestrial laser scanner data. Wind speed dependence or streamlining was observed for most of the wind direc- tions. Edge effects, i.e. the influence of the here not regarded pressure gradient and the advective terms of the momentum equation, are assumed to cause this heteroge- neity. Contrary to the hypothetic shelter effect, which would reduce the drag on sheltered plant parts, the calcu- lated profiles of drag coefficients revealed an increasing C D with PAD (i.e. a dependence on canopy and plant structure). Keywords Drag coefficient  Terrestrial laser scanning  Vegetation model  Momentum flux Introduction Detailed knowledge of momentum transfer between forest stands and the atmosphere is essential not only for assessing storm damage risks but also for understanding exchange processes of energy and greenhouse gases. The momentum absorption is dominated by inhomogeneities such as step changes in stand height and forest clearings (Hasager and Jensen 1999). Wind fields and turbulence structure within canopies are highly variable and depend on the distribution and shape of roughness elements (Raupach and Thom 1981; de Langre 2008). Intensive experiments to assess the complete mass bal- ance of several forest stands have revealed that measure- ments at discrete points unsatisfactorily represent the heterogeneity of energy and mass exchanges (Aubinet et al. 2010), and a complementary flow modelling is needed. The application of turbulence closure models that describe wind fields in tall canopies is, however, limited by the parame- terisation of plant architecture (Cescatti and Marcolla 2004). The implementation of a realistic 3D plant surface model is a prerequisite for the adequate simulation of wind fields and for making comparisons of measurements and model simulations. Terrestrial laser scanning, as a technology for close range applications, has proven to produce reliable repre- sentations of forest stand structure (Aschoff and Spiecker 2004; Gorte and Pfeifer 2004; Pfeifer and Winterhalder 2004; Henning and Radtke 2006; Maas et al. 2008). A plant area density can be estimated from laser scanning data by This article belongs to the special issue ‘Wind Effects on Trees’. Communicated by J. Bauhus. R. Queck (&)  S. Harmansa  V. Goldberg  C. Bernhofer Institute of Hydrology and Meteorology, Technische Universita ¨t Dresden, Pienner Straße 23, 01737 Tharandt, Germany e-mail: ronald.queck@tu-dresden.de URL: http://tu-dresden.de/meteorologie A. Bienert  H.-G. Maas Institute of Photogrammetry and Remote Sensing, Technische Universita ¨t Dresden, Helmholtzstraße 10, 01069 Dresden, Germany 123 Eur J Forest Res (2012) 131:165–176 DOI 10.1007/s10342-011-0550-0