Canopy model

Lamb, B D. Gay, H. Westberg, and T. Pierce, A Biogenic Hydrocarbon Emission Inventory for the U.S.A. Using a Simple Forest Canopy Model, Atmos. Environ., 27, 1673-1690 (1993). 

Toxaphene emissions for the entire United States were estimated by Li et al. [26], using application rates in the current year and residues carried over in the soil from past years, the latter estimated by assuming a 10-yr dissipation half life in soils. After the final year of toxaphene use (1986), only soil residues contributed to the emissions. Emission factors were calculated on a 1/4° latitude xl/6° longitude grid using the soil-air exchange and canopy models of Sholtz et al. [35,36]. About 80% of the emissions were from the southeastern, delta, and Appalachian states. The total quantity of toxaphene emitted to the atmosphere in 2000 was estimated as 364 tonnes. 

In practice, this big-leaf surface resistance model is an engineering tool designed for routine application. A considerably more sophisticated, multilevel canopy model has been developed for comparison purposes and to guide the future development of the big-leaf component. Details of both the engineering big-leaf model and the subcanopy model are presented elsewhere (4, 5). 

Porous canopy models may be improved by using various degrees of porosity to model individual buildings, vegetation, and other structures. 

This formulation is suitable for detailed urban canopy models (see e.g. Sections 9.2.4 and 9.2.5), when the surface is just millimetres above ground and the canopy layers are within the simulation domain. For meso-scale meteorological and NWP models in which the surface may be high above the urban canopy (average roughness level or displacement height), the SEB can be rewritten in the following form ... 

The urban canopy models considered in this paper can be also implemented as an interface / post-processor module, separated from the NWP model. In this case, the urban sublayer model will be run separately, using ready NWP data as a first approximation, and will improve the meteorological fields in an area close to the urban canopy and inside the canopy with higher resolution. 

Both of the above types of canopy are characterized by a very small fraction of the total canopy volume, so that canopy modelers can generally neglect this volume not occupied by the fluid. The same concept relates to many other types of obstructed geometries such as droplet layers, Sections 1.4 and 3.2, windmills, Section 1.4 and bubble flows, Section 7.5. Despite their diversity, many of these flows may, nevertheless, be united by the fact that one needs to account for both the internal decelerated flow within the obstructed geometry and for the external free flow over it. Field experiments in natural forests or in agricultural canopies, in wind tunnels with simulated forests of urban settlements and in water flumes with simulated aquatic vegetation have discovered many common features of these flows. These features are formalized in mathematical models. 

Coceal, O., and Belcher, S.E. (2004) A canopy model of mean winds through urban areas. Quarterly Journal of the Royal Meteorological Society, 130, 1349-1372. 

Kusaka, H Kondo, H., Kikegawa, Y., and Kimura, F. (2001) A Simple Single-Layer Urban Canopy Model for Atmospheric Models Comparison with Multi-Layer and SLAB Models, Boundary-Layer Meteorol. 101, 329-358. 

Leuning, R. (2000). Estimation of scalar source/sink di.stributions in plant canopies using Lagrangian dispersion analysis corrections for atmospheric stability and comparison with a multilayer canopy model Boundary-Layer Meteorol. 96, 293-314. 

Lamb, B., Gay, D., Westberg, H., and Pierce, T. (1993) A biogenic hydrocarbon emission inventory for the U.S.A. using a simple forest canopy model, Atmos. Environ. 27A, 1673-1690. 

Inferential Method The inferential technique for determining dry deposition rates is based on the direct application of (19.1). Measured ambient concentrations at a particular reference height are multiplied by a deposition velocity assumed to be representative of the local surface to compute the dry deposition rate. This approach is most suited when routine monitoring data are available, but the values of the derived flux values are clearly dependent on the validity of the estimates for v,j. Detailed canopy models using information about the surface and meteorology surrounding the concentration monitor can be used to calculate the deposition velocity. 

Following a similar approach to that used for low-level hcxtds, small-scale modeling is often pursued for the design of canopy hoods for a new facility or for modifications to an existing installation. >-i-24 Bender describes rests carried out... 

Sellers, P. J., Berry, J. A., Collatz, G. ]., Field, C. B. and Hall, F. G. (1992). Canopy reflectance, photosynthesis, and transpiration. III. A reanalysis using improved leaf models and a new canopy integration scheme. Remote Sens. Environ. 42,187-216. 

This model of Petty Swain (1985) is advanced and is clearly a valuable tool for tree breeders and managers. However, this model is essentially based on the individual tree and still needs to account for community and ecosystem properties such as canopy streamlining by leaf and twig flexing (Cionco, 1972). In addition, considerations of bud susceptibilities to... 

In forests, mechanical turbulence is caused by trees, and temperature inversions by the forest canopy. Ventilation inside a forest is complex and not readily described by existing air flow models (Aylor, 1976). 

The capture of acid particles, or acid droplets, by forests is considered an important cause of acidification of soils and water courses in mountain regions (Lovett, 1984 Lovett Reiners, 1986). Field experiments on the required scale are hardly feasible. Several authors have made calculations of the wind profile within the forest, and the capture efficiency of model leaves and twigs in the canopy. Figure 6.12 shows the results of calculations by Belot (1975), Slinn (1982), and Lovett (1984). When expressed in terms of the normalised velocity of deposition v., there is little difference in Fig. 6.9 between the calculated... 

Several new developments that enhance efforts to minimize drift are described. Models that predict near field effects of aircraft and mesoscale winds are available. The need for additional efforts to describe flow within canopy and description of conditions for inertial deposition on target elements is outlined. 

The AGDISP and FSCBG models accept the following meteorological data vertical wind speed and direction, temperature profile, relative wind speed, turbulence, depth of mixing layer, vertical profile of wind speed, vertical profile of wind direction, effect of canopy, and effect of complex terrain. 

We believe the major shortcoming of these models is inadequate meteorological input. In particular we need better descriptions of flow within the canopy and vertical flow profiles generated by drainage flow rather than mesoscale winds. We also need a fully operational three dimensional, complex terrain winds model. 

Dumbauld, R.K., J.R. Bjorklund and S.F. Saterlie. 1980. Computer models for predicting aircraft spray dispersion and deposition above and within forest canopies. User s Manual for the FSC BG Computer Program. Report 80-11, H E. Cramer Co., Inc., Salt Lake City, Utah. 

Modeling of Aerial Spray Drift and Canopy Penetration... 

The FSCBG aerial spray computer program is the result of more than a decade of refinement and verification of spray dispersion models used by the USDA Forest Service and the U. S. Army for predicting the drift, deposition and canopy penetration of particles and drops downwind from aircraft releases. This paper describes the mathematical framework of the models and selected applications of the models to military and Forest Service projects. 

The FSCBG aerial spray models and computer program are a result of more than a decades effort in the development, refinement and application of models for use by the U. S. Army and USDA Forest Service in predicting drift, deposition and canopy penetration from aerial releases. During the 1960 s, the U. S. 

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