Abstract
The investigation of airflow over and within forests in complex terrain has been, until recently, limited to a handful of modelling and laboratory studies. Here, we present an observational dataset of airflow measurements inside and above a forest situated on a ridge on the Isle of Arran, Scotland. The spatial coverage of the observations all the way across the ridge makes this a unique dataset. Two case studies of across-ridge flow under near-neutral conditions are presented and compared with recent idealized two-dimensional modelling studies. Changes in the canopy profiles of both mean wind and turbulent quantities across the ridge are broadly consistent with these idealized studies. Flow separation over the lee slope is seen as a ubiquitous feature of the flow. The three-dimensional nature of the terrain and the heterogeneous forest canopy does however lead to significant variations in the flow separation across the ridge, particularly over the less steep western slope. Furthermore, strong directional shear with height in regions of flow separation has a significant impact on the Reynolds stress terms and other turbulent statistics. Also observed is a decrease in the variability of the wind speed over the summit and lee slope, which has not been seen in previous studies. This dataset should provide a valuable resource for validating models of canopy flow over real, complex terrain.
Similar content being viewed by others
References
Allen T, Brown AR (2002) Large-eddy simulation of turbulent separated flow over rough hills. Boundary-Layer Meteorol 102:177–198. doi:10.1023/A:1013155712154
Ayotte KW, Davy RJ, Coppin PA (2001) A simple temporal and spatial analysis of flow in complex terrain in the context of wind energy modelling. Boundary-Layer Meteorol 98:275–295. doi:10.1023/A:1026583021740
Baldocchi D, Falge E, Gu LH, Olson R, Hollinger D, Running S, Anthoni P, Bernhofer C, Davis K, Evans R, Fuentes J, Goldstein A, Katul G, Law B, Lee XH, Malhi Y, Meyers T, Munger W, Oechel W, Paw UKT, Pilegaard K, Schmid H, Valentini R, Verma S, Vesala T, Wilson K, Wofsy S (2001) FLUXNET: a new tool to study the temporal and spatial variability of ecosystem-scale carbon dioxide, water vapor, and energy flux densities. Bull Am Meteorol Soc 82:2415–2434. doi:10.1023/A:1002497616547
Belcher SE, Hunt JCR (1998) Turbulent flow over hills and waves. Annu Rev Fluid Mech 30:507–538. doi:10.1146/annurev.fluid.30.1.507
Belcher SE, Jerram N, Hunt JCR (2003) Adjustment of a turbulent boundary layer to a canopy of roughness elements. J Fluid Mech 488:369–398. doi:10.1017/S0022112003005019
Belcher SE, Finnigan JJ, Harman IN (2008) Flows through forest canopies in complex terrain. Ecol Appl 18:1436–1453. doi:10.1890/06-1894.1
Bradley EF (1980) An experimental study of the profiles of wind speed, shearing stress and turbulence at the crest of a large hill. Q J R Meteorol Soc 106:101–123. doi:10.1002/qj.49710644708
Brown AR, Hobson JM, Wood N (2001) Large-eddy simulation of neutral turbulent flow over rough sinusoidal ridges. Boundary-Layer Meteorol 98:411–441. doi:10.1023/A:1018703209408
Cassiani M, Katul GG, Albertson JD (2008) The effects of canopy leaf area density on airflow across forest edges: large-eddy simulation and analytical results. Boundary-Layer Meteorol 126:433–460. doi:10.1007/s10546-007-9242-1
Dupont S, Brunet Y (2008) Edge flow and canopy structure: a large-eddy simulation study. Boundary-Layer Meteorol 126:51–71. doi:10.1007/s10546-007-9216-3
Dupont S, Patton EG (2012) Influence of stability and seasonal canopy changes on micrometeorology within and above an orchard canopy: The CHATS experiment. Agric For Meteorol 157:11–29. doi:10.1016/j.agrformet.2012.01.011
Dupont S, Brunet Y, Finnigan JJ (2008) Large-eddy simulation of turbulent flow over a forested hill: validation and coherent structure identification. Q J R Meteorol Soc 134:1911–1929. doi:10.1002/qj.328
Finnigan JJ (2000) Turbulence in plant canopies. Annu Rev Fluid Mech 32:519–571. doi:10.1146/annurev.fluid.32.1.519
Finnigan JJ (2008) An introduction to flux measurements in difficult conditions. Ecol Appl 18:1340–1350. doi:10.1890/07-2105.1
Finnigan JJ, Belcher SE (2004) Flow over a hill covered with a plant canopy. Q J R Meteorol Soc 130:1–29. doi:10.1256/qj.02.177
Finnigan JJ, Brunet Y (1995) Turbulent airflow in forests on flat and hilly terrain. In: Coutts MP, Grace J (eds) Wind and trees. Cambridge University Press, Cambridge, pp 3–40
Foken T, Wichura B (1996) Tools for quality assessment of surface-based flux measurements. Agric For Meteorol 78:83–105. doi:10.1016/0168-1923(95)02248-1
Gardiner B, Blennow K, Carnus JM, Fleischer P, Ingemarson F, Landmann G, Lindner M, Marzano M, Nicoll B, Orazio C, Peyron JL, Reviron MP, Schelhaas MJ, Schuck A, Spielmann M, Usbeck T (2010) Destructive storms in European forests: past and forthcoming impacts. Final Report to European Commission DG Environment. Online. http://ec.europa.eu/environment/forests/fprotection.htm
Gardiner B, Schuck A, Schelhaas MJ, Orazio C, Blennow K, Nicoll B (eds) (2013) Living with storm damage to forests: what science can tell us 3. European Forest Institute. http://www.efi.int/files/attachments/publications/efi_wsctu_3_final_net.pdf
Hanewinkel M, Cullmann D, Schelhaas M, Nabuurs GJ, Zimmermann N (2013) Climate change may cause severe loss in the economic value of European forest land. Nat Clim Change 3:203–207. doi:10.1038/nclimate1687
Hunt JCR, Leibovich S, Richards KJ (1988) Turbulent shear flow over low hills. Q J R Meteorol Soc 114:1435–1470. doi:10.1002/qj.49711448405
Irvine MR, Gardiner BA, Hill MK (1997) The evolution of turbulence across a forest edge. Boundary-Layer Meteorol 84:467–496. doi:10.1023/A:1000453031036
Justus CG, Hargreaves WR, Yalcin A (1976) Nationwide assessment of potential output from wind-powered generators. J Appl Meteorol 15:673–678. doi:10.1175/1520-0450(1976)015<0673:NAOPOF>2.0.CO;2
Kaimal JC, Finnigan JJ (1994) Atmospheric boundary layer flows: their structure and measurements. Oxford University Press, New York 289 pp
Lee X, Finnigan J, Paw UKT (2004) Coordinate systems and flux bias error. In: Lee X, Massman W, Law B (eds) A handbook of micrometeorology: a guide for surface flux measurements. Kluwer, Dordrecht, pp 33–66
Miller DR, Lin JD, Lu ZN (1991) Air flow across an alpine forest clearing: a model and field measurements. Agric For Meteorol 56:209–225. doi:10.1016/0168-1923(91)90092-5
Morse AP, Gardiner BA, Marshall BJ (2002) Mechanisms controlling turbulence development across a forest edge. Boundary-Layer Meteorol 103:227–251. doi:10.1023/A:1014507727784
Neff DE, Meroney NR (1998) Wind-tunnel modelling of hill and vegetation influence on wind-power availability. J Wind Eng Ind Aerodyn 74:335–343. doi:10.1016/S0167-6105(98)00030-0
Patton EG, Katul GG (2009) Turbulent pressure and velocity perturbations induced by gentle hills covered with sparse and dense canopies. Boundary-Layer Meteorol 133:189–217. doi:10.1007/s10546-009-9427-x
Poggi D, Katul GG (2007a) An experimental investigation of the mean momentum budget inside dense canopies on narrow gentle hilly terrain. Agric For Meteorol 144:1–13. doi:10.1016/j.agrformet.2007.01.009
Poggi D, Katul GG (2007b) Turbulent flows on forested hilly terrain: the recirculation region. Q J R Meteorol Soc 133:1027–1039. doi:10.1002/qj.73
Quine C, Gardiner BA (2007) Understanding how the interaction of wind and trees results in windthrow, stem breakage and canopy gap formation. In: Johnson E, Miyanishi K (eds) Plant disturbance ecology: the process and the response. Academic Press, Burlington, pp 103–155
Raupach MR, Finnigan JJ, Brunet Y (1996) Coherent eddies and turbulence in vegetation canopies: the mixing length analogy. Boundary-Layer Meteorol 78:351–382. doi:10.1007/BF00120941
Romniger JT, Nepf HM (2011) Flow adjustment and interior flow associated with a rectangular porous obstruction. J Fluid Mech 680:636–659. doi:10.1017/jfm.2011.199
Ross AN (2008) Large eddy simulations of flow over forested ridges. Boundary-Layer Meteorol 128:59–76. doi:10.1007/s10546-008-9278-x
Ross AN (2011) Scalar transport over forested hills. Boundary-Layer Meteorol 141:179–199. doi:10.1007/s10546-011-9628-y
Ross AN, Baker TP (2013) Flow over partially forested ridges. Boundary-Layer Meteorol 146. doi:10.1007/s10546-012-9766-x
Ross AN, Vosper SB (2005) Neutral turbulent flow over forested hills. Q J R Meteorol Soc 131:1841–1862. doi:10.1256/qj.04.129
Ruck B, Adams E (1991) Fluid mechanical aspects of the pollutant transport to coniferous trees. Boundary-Layer Meteorol 56:163–195. doi:10.1007/BF00119966
Vosper SB, Mobbs SD, Gardiner BA (2002) Measurements of the momentum budget in flow over a hill. Q J R Meteorol Soc 128:2257–2280. doi:10.1256/qj.01.11
Webster S, Brown AR, Cameron DR, Jones CP (2003) Improvements to the representation of orography in the Met Office Unified Model. Q J R Meteorol Soc 129:1989–2010. doi:10.1256/qj.02.133
Zeri M, Rebmann C, Feigenwinter C, Sedlak P (2010) Analysis of short periods with strong and coherent CO\(_{2}\) advection over a forested hill. Agric For Meteorol 150(5):674–683. doi:10.1016/j.agrformet.2009.12.003
Acknowledgments
This work was funded by the Natural Environmental Research Council (NERC) grant NE/C003691/1. ERG would like to acknowledge additional support through a NERC Collaborative Award in Science and Engineering (CASE) award with Forest Research. We would like to thank Ian Brooks and all those from the Universities of Leeds and Edinburgh, the Forestry Commission, Forest Research and from the Met Office Research Unit at Cardington who loaned us equipment and assisted in the field campaign.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Grant, E.R., Ross, A.N., Gardiner, B.A. et al. Field Observations of Canopy Flows over Complex Terrain. Boundary-Layer Meteorol 156, 231–251 (2015). https://doi.org/10.1007/s10546-015-0015-y
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s10546-015-0015-y