[Characterisation of the atmospheric dispersal and flow of latent heat in cork-oak groves]
2003
Rodrigues, A.M. (EStacao Florestal Nacional, Oeiras (Portugal). Dept. de Silvicultura e Produtos Florestais) | Pita, G.P.A. (Instituto Superior Tecnico, Lisbon (Portugal). Dept. de Engenharia Mecanica)
At an observation tower in a cork oak stand, experimental measurements were made of the usual micrometeorological variables and of the turbulent fluctuations of wind velocity components and air temperature, in order to characterize their influence on the evapotranspiration regime and, by inspection of the Penman-Monteith equation, as well as time and frequency domain analysis of turbulent flow. The total mean daily ratio between the latent heat flux and equilibrium evapotranspiration was 0.44, typical of a dry canopy. The mean daily value of the coupling coefficient was 0.18, representative of an imposed evaporation, with a strong dependence on atmospheric humidity and canopy resistance. Canopy resistance increased during the afternoon, with an increasing atmospheric vapor pressure deficit, indicating a partial stomatal closure. The spectra of air temperature and velocity components fitted well with the usual empirical functions. The slopes of spectral curves followed the -2/3 power law in the inertial subrange. The calculated mean integral eulerian length scales, relating to tree heights, calculated from autocorrelation functions, for the horizontal and vertical velocity components of wind velocity, were 8.65 and 0.69. Their corresponding time scales were 12 and 0.96 s. An application of the quadrant method confirmed the importance of intermittent sweeps and ejections, in the descendent transport of horizontal momentum
Mostrar más [+] Menos [-]Palabras clave de AGROVOC
Información bibliográfica
Este registro bibliográfico ha sido proporcionado por Ministério da Agricultura, Desenvolvimento Rural e Pescas