Flow Field Within and Above a Forest Canopy: Task I: Study of Airflow in Simulated Temperate and Tropical Forest Canopies
Flow Field Within and Above a Forest Canopy: Task I: Study of Airflow in Simulated Temperate and Tropical Forest Canopies

Author: W. Z. Sadeh

Publisher:

Published: 1969

Total Pages: 71

ISBN-13:

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The velocity and longitudinal turbulence intensity distributions inside and above a forest canopy along its center line were investigated. For this purpose a model forest canopy was used in a meteorological wind tunnel. The results indicate that the flow may be divided into an entrance and fully developed region followed by a short adjustment distance close to canopy end. The entrance region has a decisive effect on the flow characteristics through the canopy. The velocity and turbulence inside the canopy are strongly affected by its structure. A similar qualitative variation for both velocity and turbulence was found in and above the canopy. Its influence stretches over more than 4 roughness heights above it. Generally, the results are in relatively reasonable agreement with field measurements. Investigation of the modified logarithmic law for describing the velocity profile above the canopy revealed that both flow parameters, i.e., friction velocity and roughness length, are not local constants. On the contrary, they vary drastically with height. It is suspected that this is due to the fact the assumption of constant shear stress throughout the boundary layer or significant portions of it is not satisfied. (Author).

Numerical Simulation of Canopy Flows
Numerical Simulation of Canopy Flows

Author: Günter Groß

Publisher: Springer Science & Business Media

Published: 2012-12-06

Total Pages: 243

ISBN-13: 364275676X

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Starting with the description of meteorological variables in forest canopies and its parameter variations, a numerical three-dimentional model is developed. Its applicability is demonstrated, first, by wind sheltering effects of hedges and, second, by the effects of deforestation on local climate in complex terrain. Scientists in ecology, agricultural botany and meteorology, but also urban and regional lanners will profit from this study finding the most effective solution for their specific problems.

Application of the Ideal Canopy Flow Concept to Natural and Artificial Roughness Elements
Application of the Ideal Canopy Flow Concept to Natural and Artificial Roughness Elements

Author: R. M. Cionco

Publisher:

Published: 1971

Total Pages: 206

ISBN-13:

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Effort has been expended in modeling air flow within and above simple roughness elements for neutral steady-state conditions. Application of the ideal canopy flow concept suggested by Cionco, Ohmstede and Appleby is now extended to various natural and artificial canopies of simple or complex structure. Properties and characteristics considered were: Shape of the unit canopy wind profile, intensity of turbulence magnitudes, an index of canopy flow, and the effects of density and flexibility variations upon the flow. The profile shape is characteristic and best described by an exponential relationship within simple-structured elements. In complex structures, the profiles exhibited low-level maximums and no-gradient layers. Above the vegetation, the logarithmic wind relation was valid for each canopy type. Intensity of turbulence was relatively uniform with height for simple canopies and significantly non-uniform with height in complex structures, with large leaf area maximums and very low wind speeds. The ideal canopy flow concept can potentially serve many disciplines and efforts besides micrometeorology and diffusion research. If to serve no other purpose, it can be used to establish the initial formulation of a boundary condition or minor portion of a larger problem. The mathematical simplicity of the concept may be its most important quality when it is to be used as part of a larger system of equations.

Scientific and Technical Aerospace Reports
Scientific and Technical Aerospace Reports

Author:

Publisher:

Published: 1995

Total Pages: 488

ISBN-13:

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Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.

The Forest-Atmosphere Interaction
The Forest-Atmosphere Interaction

Author: B.A. Hutchison

Publisher: Springer Science & Business Media

Published: 2012-12-06

Total Pages: 683

ISBN-13: 9400953054

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The effects of meteorological phenomena upon forest produc tivity and forestry operations have been of concern for many years. With the evolution of system-level studies of forest eco system structure and function in the International Biological Program and elsewhere, more fundamental interactions between forest ecosystems and the atmosphere received scientific atten tion but the emphasis on meteorological and climatological effects on forest processes remained. More recently, as recogni tion has developed of potential and actual problems associated with the atmospheric transport, dispersion, and deposition of airborne pollutants, the effects of forest canopies upon boundary-layer meteorological phenomena has come under scientific scrutiny. Looking to the future, with rising atmospheric con centrations of C02 and increasing competition for the finite fresh-water resources of the earth, interest in the role of forests in global C02 and water balances can also be expected to intensify. Thus, the nature of forest canopy-atmosphere interac tions, that is to say, the meteorological phenomena occurring in and above forest canopies, are of importance to a wide variety of scientific and social-issues. Demands for forest meteorological information currently exceed levels of knowledge and given the economic constraints of science in general and environmental sciences in particular, chances for major improvements in scien tific support in the near future are slim. Unfortunately, studies of environmental phenomena in and above forests are costly and logistically difficult. Trees, the ecological dominants of forest ecosystems, are the largest of all terrestrial organisms.

A Preliminary Field Study of Turbulent Flow Over and Inside a Forest Edge
A Preliminary Field Study of Turbulent Flow Over and Inside a Forest Edge

Author: J. D. Lin

Publisher:

Published: 1985

Total Pages: 116

ISBN-13:

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This study focused on field measurements to determine the spatial variability of the turbulence characteristics under various atmospheric and forest canopy conditions. A high-speed multi-channel data acquisition system was configured and tested. Fixed and movable observation towers have been set up in the University experimental forest in Coventry, Conn. Two wind velocity sensors, being tested and evaluated in the laboratory for their capability to measure the three-dimensional flow with high turbulence intensity that generally characterizes the flow regime in a forest canopy; are a dual triple-split hot-film probe and a tri-diagonal hot-film probe with a wind octant electronic sensor (WOES). The response of WOES tested in the low-speed wind nozzle appears to be promising and its compatibility with the tri-diagonal hot-film probe is being evaluated. A number of field measures has been conducted over and inside the forest canopy, using a vertical array of velocity sensors which includes a propeller anemometer, and x-hot wire and hot film anemometers.