Abstract
Ramp patterns of temperature and humidity occur coherently at several levels within and above a deciduous forest as shown by data gathered with up to seven triaxial sonic anemometer/thermometers and three Lyman-alpha hygrometers at an experimental site in Ontario, Canada. The ramps appear most clearly in the middle and upper portion of the forest. Time/height cross-sections of scalar contours and velocity vectors, developed from both single events and ensemble averages of several events, portray details of the flow structures associated with the scalar ramps. Near the top of the forest they are composed of a weak ejecting motion transporting warm and/or moist air out of the forest followed by strong sweeps of cool and/or dry air penetrating into the canopy. The sweep is separated from the ejecting air by a sharp scalar microfront. At approximately twice the height of the forest, ejections and sweeps are of about equal strength.
In the middle and upper parts of the canopy, sweeps conduct a large proportion of the overall transfer between the forest and the lower atmosphere, with a lesser contribution from ejections. Ejections become equally important aloft. During one 30-min run, identified structures were responsible for more than 75% of the total fluxes of heat and momentum at mid-canopy height. Near the canopy top, the transition from ejection of slow moving fluid to sweep bringing fast moving air from above is very rapid but, at both higher and lower levels, brief periods of upward momentum transfer occur at or immediately before the microfront.
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References
Antonia, R. A., Chambers, A. J., Friehe, C. A., and Van Atta, C. W.: 1979, ‘Temperature Ramps in the Atmospheric Surface Layer’, J. Atmos. Sci. 36, 99–108.
Baldocchi, D. D. and Meyers, T. P.: 1988, ‘Turbulence Structure in a Deciduous Forest’, Boundary-Layer Meteorol. 43, 345–364.
Bogard, D. G. and Tiederman, W. G.: 1986, ‘Burst Detection with Single-point Velocity Measurements’, J. Fluid Mech. 162, 389–413.
Busch, N. E.: 1973, ‘On the Mechanics of Atmospheric Turbulence’, in D. A. Haugen (ed.), Workshop on Micrometeorology, Amer. Meteorol. Soc., Boston, pp. 1–65.
Chen, C. P. and Blackwelder, R. F.: 1978, ‘Large-scale Motion in a Turbulent Boundary Layer: a Study Using Temperature Contamination’, J. Fluid Mech. 89, 1–31.
Chiba, O.: 1978, ‘Stability Dependence of the Vertical Velocity Skewness in the Atmospheric Surface Layer’, J. Meteorol. Soc. Japan. 56, 140–142.
Corino, E. R. and Brodkey, R. S.: 1969, ‘A Visual Investigation of the Wall Region in Turbulent Flow’, J. Fluid Mech. 37, 1–30.
Denmead, O. T. and Bradley, E. F.: 1987, ‘On Scalar Transport in Plant Canopies’, Irrigation Sci. 8, 131–149.
Finnigan, J. J.: 1979a, ‘Turbulence in Waving Wheat. I Mean Statistics and Honami’, Boundary-Layer Meteorol. 16, 181–211.
Finnigan, J. J.: 1979b, ‘Turbulence in Waving Wheat. II Structure of Momentum Transfer’, Boundary-Layer Meteorol. 16, 213–236.
Kaimal, J. C.: 1974, ‘Translation Speed of Convective Plumes in the Atmospheric Surface Layer’, Quart. J. Roy. Meteorol. Soc. 100, 46–52.
Kaimal, J. C. and Businger, J. A.: 1970, ‘Case Studies of a Convective Plume and a Dust Devil’, J. Appl. Meteorol. 9, 612–620.
Kline, S. J., Reynolds, W. C., Schraub, F. A., and Rundstadler, P. W.: 1967, ‘The Structure of Turbulent Boundary Layers’, J. Fluid Mech. 30, 741–773.
Legg, B. J. and Monteith, J. L.: 1975, ‘Heat and Mass Transfer in Plant Canopies’, in D. A. De Vries and N. H. Afgan (eds.), Heat and Mass Transfer in the Biosphere, Wiley, New York, pp. 167–186.
Meyers, T. P. and Paw U. K. T.: 1986, ‘Testing of a Higher-order Closure Model for Airflow within and above Plant Canopies’, Boundary-Layer Meteorol. 37, 297–311.
Meyers, T. P. and Paw U. K. T.: 1987, ‘Modelling the Plant Canopy Micrometeorology with Higher-order Closure Principles’, Agric. Forest. Meteorol. 41, 143–163.
Neumann, H. H., den Hartog, G., and Shaw, R. H.: 1988, ‘Leaf Area Measurements During Leaf-fall for a Deciduous Forest Based on Hemispheric Photographs and Leaf-litter Collection’, Agric. Forest Meteorol., in press.
Offen, G. R. and Kline, S. J.: 1975, ‘A Proposed Model of the Bursting Process in Turbulent Boundary Layers’, J. Fluid Mech. 70, 209–228.
Praturi, A. K. and Brodkey, R. S.: 1978, ‘A Stereoscopic Visual Study of Coherent Structures in Turbulent Shear Flow’, J. Fluid Mech. 89, 251–272.
Priestley, C. H. B.: 1959, Turbulent Transfer in the Lower Atmosphere, University of Chicago Press, Chicago, pp. 53–72.
Rajagopalan, S. and Antonia, R. A.: 1980, ‘Interaction between Large and Small Scale Motions in a Two-dimensional Turbulent Flow Duct’, Phys. Fluids 23, 1101–1110.
Raupach, M. R.: 1981, ‘Conditional Statistics of Reynolds Stress in Rough-wall and Smooth-wall Turbulent Boundary Layers’, J. Fluid Mech. 108, 363–382.
Raupach, M. R.: 1987, ‘A Lagrangian Analysis of Scalar Transfer in Vegetation Canopies’, Q. J. Roy. Meteorol. Soc. 113, 107–120.
Raupach, M. R. and Thorn, A. S.: 1981, ‘Turbulence in and above Plant Canopies’, Ann. Rev. Fluid Mech. 13, 97–129.
Schols, J. L. J.: 1984, ‘The Detection and Measurement of Turbulent Structures in the Atmospheric Surface Layer’, Boundary-Layer Meteorol. 29, 39–58.
Shaw, R. H., den Hartog, G., and Neumann, H. H.: 1988, ‘Influence on Foliar Density and Thermal Stability on Profiles of Reynolds Stress and Turbulence Intensity in a Deciduous Forest’, Boundary-Layer Meteorol. 45, 391–409.
Shaw, R. H., Tavangar, J., and Ward, D. P.: 1983, ‘Structure of the Reynolds Stress in a Canopy Layer’, J. Clim. Appl. Meteorol. 22, 1922–1931.
Shaw, R. H. and Seginer, I.: 1987, ‘Calculation of Velocity Skewness in Real and Artificial Plant Canopies’, Boundary-Layer Meteorol. 39, 315–332.
Subramanian, C. S., Rajagopalan, S., Antonia, R. A., and Chambers, A. J.: 1982, ‘Comparison of Conditional Sampling and Averaging Techniques in a Turbulent Boundary Layer’, J. Fluid Mech. 123, 335–362.
Talmon, A. M., Kunen, J. M. G., and Ooms, G.: 1986, ‘Simultaneous Flow Visualization and Reynolds-stress Measurement in a Turbulent Boundary Layer’, J. Fluid Mech. 163, 459–478.
Taylor, R. J.: 1958, ‘Thermal Structures in the Lowest Layer of the Atmosphere’, Australian J. Phys. 11, 168–176.
Thomas, A. S. and Bull, M. K.: 1983, ‘On the Role of the Wall-Pressure Fluctuations in Deterministic Motions in the Turbulent Boundary Layer’, J. Fluid Mech. 128, 283–322.
Wallace, J. M., Eckelmann, H., and Brodkey, R. S.: 1972, ‘The Wall Region in Turbulent Shear Flow’, J. Fluid Mech. 54, 39–48.
Wilczak, J. M.: 1984, ‘Large-scale Eddies in the Unstably Stratified Atmospheric Surface Layer. Part I: Velocity and Temperature Structure’, J. Atmos. Sci. 41, 3537–3550.
Wilczak, J. M. and Businger, J. A.: 1984, ‘Large-scale Eddies in the Unstably Stratified Atmospheric Surface Layer. Part II: Turbulent Pressure Fluctuations and the Budgets of Heat Flux, Stress and Turbulent Kinetic Energy’, J. Atmos. Sci. 41, 3551–3567.
Wilczak, J. M. and Tillman, J. E.: 1980, ‘The Three-dimensional Structure of Convection in the Atmospheric Surface Layer’, J. Atmos. Sci. 37, 2424–2443.
Wilson, N. R. and Shaw, R. H.: 1977, ‘A Higher Order Closure Model for Canopy Flow’, J. Appl. Meteorol. 16, 1197–1205.
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© 1989 Kluwer Academic Publishers
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Gao, W., Shaw, R.H., Paw U, K.T. (1989). Observation of Organized Structure in Turbulent Flow within and above a Forest Canopy. In: Munn, R.E. (eds) Boundary Layer Studies and Applications. Springer, Dordrecht. https://doi.org/10.1007/978-94-009-0975-5_22
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DOI: https://doi.org/10.1007/978-94-009-0975-5_22
Publisher Name: Springer, Dordrecht
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