Vegetative canopies in meteorology

Intensive investigations in this field were started in 1950 and 1960 [6, 343, 410, 520], The first theoretical considerations were suggested in the works of Inoue, Cionco, Lemon, Cowan, and Menzhulin [155,407,409, 522], The recent state of the field has been summarized in the publications of Raupach and Thom, Dubov et al. (1981), Finnigan (2000) [155, 187, 522], as well as in Chapters 4 and 5 of this book. Let us briefly consider the most significant results in this field. 

Within the canopy stands, the air motion is significantly decelerated, but nevertheless it is of a considerable value and evidently of vital importance for agrometeorolog-ical practice. The internal motion is expected to be less or more depended also on how dense is the vegetated layer. The most popular relation derived theoretically by Inoue 

It is also worth noting that the early measurements in forests or in agricultural stands were done with the use of mechanical cup-anemometers placed on several levels of high masts, as was mentioned in [186], Because of their inertia, they were adequate for recording the average speeds, but insufficient to reflect the turbulence properties. 

Nowadays, one applies mainly sonic anemometers in meteorological measurements, [186], 

Turbulence of the flow is greatly increased inside the canopy. Turbulence intensity divided by mean longitudinal velocity has been shown in the Fig. 1.1 for several types of forests, [155], The high level of the turbulence, up to 40% and 60%, can be attributed to vortices in the flow shed from obstructions like tree branches, trunks, and leaves constituting the forest. 

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