Vegetation canopy

Subsurface runoff. When precipitation hits the land surface, the vast majority does not go directly into the network of streams and rivers in fact, it may be cycled several times before ever reaching a river and the ocean. Instead, most precipitation that is not intercepted by the vegetation canopy and re-evaporated infiltrates into the soil, where it may reside as soil moisture, percolate down to ground-water, or be transpired by plants. 

Slinn, W. G. N., Predictions for Particle Deposition to Vegetative Canopies, Atmos. Environ., 16, 1785-1794 (1982). 

Chukhlantsev A.A. (2006). Microwave Radiometry of Vegetation Canopies. Springer-Verlag, Berlin, 287 pp. 

Slinn, W.G.N. (1982) Predictions for particle deposition to vegetative canopies. Atmospheric Environment, 16,1785-94. 

Figure 9. Comparison of normalized wind profiles of various vegetative canopies where Z is the height above the ground, H is the height of the top of the canopy and D is wind speed. 1, dense cotton (21) 2, Douglas fir forest (19) 3, dense conifer with understory (22) 4, moderately dense conifer stand with no understory (20) 5, dense hardwood jungle with understory (23) and 6, isolated conifer stand (24).

Raupach M. (2001) Inferring biogeochemical sources and sinks from atmospheric concentrations general consideration and applications in vegetation canopies. In Global Biogeochemical Cycles in the Climate System (eds. E. D. Schulze, M. Heimann, S. Harrison, E. Holland, J. Lloyd, I. C. Prentice, and D. Schimel). Academic Press, pp. 41-60. 

Figure 1.1 Prandtl s [510] qualitative idea of the air flow in vegetative canopies 1 - logarithmic portion of the wind profile 2 - distorted profile portion.

In this Eulerian theoretical approach, a number of obstructions is considered as a continuous medium, or even media. They may have their own motion, for example, the waving of leafs in the case of vegetation canopy. In the case of droplets, their motion in the vertical direction and along the wind can be described by the following momentum equation for each size r ... 

Large-eddy simulation output is a three-dimensional, time-dependent flow and scalar field. The results are unique in reproducing most aspects of the turbulent flow field and its interaction with a layer of vegetation. Due to the considerable demand on computational resources, it is not yet reasonable to utilize a grid network that can sufficiently resolve a vegetation canopy and, at the same time, extend both horizontally and vertically to simulate a full atmospheric boundary layer. Nevertheless, even simulations with quite limited vertical extent, as few as three canopy heights, have been successful in accurately reproducing the features described earlier. 

The distributed array of drag elements in vegetation canopies creates a mean wind profile that contains an elevated shear layer centred near the canopy top that more closely approximates a plane mixing layer than a wall layer. This velocity stmcture is responsible for turbulence characteristics that differ substantially from those over a smooth surface. Velocity spectra are sharply peaked, streamwise and vertical velocities have probability densities that are strongly skewed, streamwise and vertical velocities are correlated more strongly that would be expected over a smoother surface, and transport is dominated by coherent flow structures with sweeps more important than ejections. 

Ayotte, K.W., Finnigan, J.J., and Raupach, M.R. (1998) A second order closure for neutrally stratified vegetative canopy flows, Boundary-Layer Meteorol 90, 189-216. 

Fitzmaurice, L., Shaw, R.H., Paw U.K.T., and Patton, E.G. (2004) Three-dimensional scalar microfront systems in a large-eddy simulation of vegetation canopy How, Boundary-Layer Meteor. 112, 107-127. 

Hunt, J.C.R., Grinchenko, V.T., and Gayev, Ye.A. (2004) NATO Advanced Study Institute PST.ASI.980064 Flow and Transport Processes in Complex Obstructed Geometries from cities and vegetative canopies to industrial problems. Kyiv (Ukraine), May 4-15, 2004. ERCOFTAC Bulletin. 63, 27- 31. 

Menzhulin, G.V. (1972) On aerodynamics parameters of vegetation canopy, Proc. of Main Geophysical Observatory (GGO). Iss. 282, 133-143. 

Raupach, M.R., and Shaw, R.H. (1982) Averaging procedures for flow within vegetation canopies, Boundary-Layer Meteorol. 22, 79-90. 

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