





<-■■;' 







"-^^i^^^^ 







.Mi^.^ 



Figure 9. Close-up of air canopy probes. 



Several typical results from the micrometeorological tower data are given in Table IV. Through- 

 out the summer, temperature profiles were nearly isothermal or showed slight inversions. Stabilities 

 were therefore neutral or slightly stable. Wind profiles were close to logarithmic and yielded rough- 

 ness parameters between 1 and 2 cm. The roughness parameters enter the computations of the eddy 

 heat flux, as an important terrain type specification. 



Canopy temperatures for various manipulations provided interesting data on the effects of the 

 vegetation upon the thermal regime of the tundra surface. Temperature profiles were measured within 

 clip and cleared and mulched vegetative canopies as well as within a natural (control) canopy (Table 

 V). Temperatures within the mulched canopy are generally 1-2°C higher in the top layers of the 

 15-cm-high canopy, where material has been added artificially, but are about the same as in the 

 other plots in the lower layers. The vertical temperature profile in the mulched layer is therefore 

 close to isothermal, whereas the clip and cleared plot shows temperature increases in the layer up 

 to 2°C, with higher temperatures at the soil surface. The control plot also shows temperature in- 

 crease with depth in the vegetation, but direct heating of the surface by radiation is not as pro- 

 nounced, owing to higher leaf area indices. The vertical wind structure in the natural and disturbed 

 canopies remains to be measured with hot-wire anemometers now available to the project. 



Radiative energy inputs and outputs by reflection and thermal emission were measured at several 

 sites. Table VI gives the mean incoming short-wave radiation for 10-day periods obtained from the 

 Barrow Weather Bureau. The radiative flux divergences within the vegetaticm layer were computed 

 from these values and the mean measured extinction profiles. Extinction profiles as a function of 

 seasonal changes of the leaf area index will be computed. 



18 



