specified while the turbulent correlations have zero gradient. At the 

 lower boundary, the mean velocities are zero while the temperature is 

 specified . Gradients of all turbulent correlations are zero, except w^ 

 and wc which are given from sublayer relationships similar to Equations 

 (9) and (10). 



Detailed measurements of mean flow variables and turbulent 

 correlations within vegetated hydraulic environments are unavailable at 

 the present time. Therefore, for model verification, we used the 

 detailed flow measurements within a corn canopy obtained by Shaw 

 et al, (lU). 



The vertical profile of plant area density of the canopy is shown 

 in Figure 7. ^e used the measured distribution of Ah shown in Figure 6 

 as Af-h; a=0.1 and C =0.16. C Ay/A|. was given a value of 1 such that 

 the skin friction drag is about one-third of the profile drag within 

 the canopy, a relation measured experimentally by Thorn (18). Based on 

 these parameters, our model predictions agree closely with the measured 

 mean longitudinal velocity Reynolds stress, and standard deviation of 

 longitudinal and vertical velocities (Figures). Most of the momentum 

 is absorbed within the upper part of the canopy and little is 

 transported to the ground. 



"4 



W///,y//y,.:-. 

 Smoott 

 (urfoce 



R, (T) Outer bounflory 



lOyer 



Rj @ Corttort flui 



(Oyer 



Rj \ ^) Vijdolior eonopy 



(<) Subloye' • leovej or 

 olhei tmoolh turfocti 



z/h 



Fig. 6. Four regions of planetary 

 or oceanic boundary layer 

 in the presence of vege- 

 tation canopies. Rj.Ra. 

 R3, and Rm indicate 

 resistance to species 

 deposition. 



Fig. 7. Profile of plant area 

 density of a corn 

 canopy. 



The same basic model was applied to simulate the heat transfer 

 within the corn canopy measured by Shaw et al . in October 1971. The 

 crop changed from 290 era tall at the beginning of the experiment on 



243 



