Abel Martins Rodrigues*1 e Gabriel Paulo Alcântara Pita**
*Investigador Auxiliar
Estação Florestal Nacional. Departamento de Silvicultura e Produtos Florestais, Av. da República, Quinta do Marquês. 2780-149 OEIRAS
** Professor Auxiliar
Departamento de Engenharia Mecânica. Instituto Superior Técnico, Av. Rovisco Pais, 1049-001 LISBOA
Sumário. Para uma caracterização físico-ambiental do montado de sobro e verificação da aplicabilidade e generalização ao montado de sobro dos padrões gerais de funcionamento físico-ambiental dos ecossistemas florestais, procedeu-se à medição, numa torre de 16m de altura, na camada de fluxo constante do balanço radiativo, dos fluxos turbulentos de calor latente e sensível, pelos métodos de covariância turbulenta e aerodinâmico iterativo e dos diversos termos de armazenamento energético. As campanhas de aquisição de dados no campo decorreram em dezasseis dias sem precipitação nos períodos de Maio a Outubro dos anos de 1997, 1998 e 1999. A média total dos valores médios diários das razões entre o somatório dos fluxos turbulentos, obtidos pelo método de covariância turbulenta e o balanço radiativo foi de 77%, valor típico para ecossistemas florestais. O fecho do balanço energético apresentou uma boa qualidade. Os valores de fluxo de calor sensível aumentaram com os correspondentes de balanço radiativo e velocidade de fricção. Verificou-se também uma relação indirecta entre o fluxo de calor latente e o balanço radiativo, típica de cobertos florestais.
Palavras-chave: montado; camada limite; balanço energético; fecho; evaporação; qualidade
]]>Abstratct. A physical characterization of cork oak stands in order to verify the applicability and generalization to that ecosystem of general environmental physical principles of forests was made. At a 16m tower in a cork oak stand, experimental measurements were done, in the constant flux layer of net radiation, of latent and sensible turbulent heat fluxes, by eddy covariance and aerodynamic methods and of the storage energy terms. The field campaigns for measurements were made in sixteen days in the periods of May-October of 1997, 1998 and 1999. The total mean daily ratio between the sum of the turbulent fluxes and net radiation was 77%, typical of data of forest canopies. A reasonable energy budget closure quality was obtained. The sensible heat fluxes increased mainly with net radiation and friction velocity. An indirect relation between latent heat flux and net radiation, typical of forest ecosystems, was shown.
Keywords: cork oak stand; boundary layer; energy budget; closure; evaporation; quality
Résumé. Afin de faire une caractérisation physique et ambiantale du peuplement de chêne-liège, vérification de l'applicabilité et de la généralisation des modèles généraux du fonctionnement physique et ambiantale des écosystèmes forestiers l'étude suivante a été réalisée. Á partir d'une tour de 16 m de hauteur, le mesurage des flux turbulents de chaleur latente et sensible a été effectué dans la couche de flux constant du bilan radiatif par des méthodes de covariance turbulente et d'aérodynamique itérative et en plusieurs termes d'emmagasinage énergétique. Les campagnes de récolte de données sur le terrain ont eu lieu en seize jours, sans précipitation, entre Mai et Octobre au cours des années 1997, 1998 et 1999. La moyenne totale des valeurs moyennes quotidiennes des rapports entre la somme des flux turbulents obtenus par la méthode de co-variance turbulente et le bilan radiatif a été de 77%, une valeur typique des systèmes forestiers. La fermeture du bilan énergétique a présenté une bonne qualité. Les valeurs de flux de la chaleur sensible ont augmenté en correspondance avec le bilan radiatif et la vitesse de friction. Le rapport indirecte entre le flux de chaleur latente et le bilan radiatif, typique des couverts forestiers, a aussi été vérifié.
Mots clé:peuplements de chêne-liège; couche limite; bilan énergétique; fermeture; évaporation; qualité
Texto completo disponível apenas em PDF.
Full text only available in PDF format.
]]> Bibliografia
Anthoni, P.M., Beverly, E.L., Unsworth,. M.H.,Vong, R.J., 2000. Variation of Net Radiation Over Heterogeneous Surfaces: Measurements and Simulation in a Juniper-Sagebrush ecosystem. Agricultural and Forest Meteorology 102, 275-286 [ Links ]
Aston, A.R., 1985. Heat Storage in a Young Eucalipt Forest. Agricultural and Forest Meteorology 35 : 281-297 [ Links ]
Aubinet, M., Grelle, A., Ibrom, A., Rannik, Ü., Moncrieff, J., Foken, T., Kowalski, A.S., Martin, P.H.M., Berbigier, P., Bernhofer, Ch., Clement, R., Elbers, J., Granier, A., Grünwald, T., Morgenstern, K., Pilegaard, K., Rebmann, C., Snidjers, W., Valentini, R., Vesala, T., 2000. Estimates of the Annual Net Carbon and Water Exchange of Forests: The Euroflux Methodology. Advances in Ecological Research 30. [ Links ]
Baldocchi, D.D., Hutchinson, B.A., 1987. Turbulence in a Almond Orchard: Vertical Variations in Turbulent Statistics. Boundary Layer Meteorology 40 : 127-146 [ Links ]
Baldocchi, D.D., UT. Paw, K., Shaw, R.H., Snyder, R.L., 1995. Advanced Short Course on Biometeorology and Micrometeorology. CNR, CIHEAM, Università di Sassari, EU, Sassari, Italy [ Links ]
Baldocchi, D.D., Vogel, A.C., Hall, B., 1997. Seasonal Variation of Energy and Water Vapor Exchange Rates Above and Below a Boreal Jack Pine Forest Canopy. Journal of Geophysical Research 102 : 28939-28951 [ Links ]
Blanken, P.D., Black, T.A., Yang, P.C., Neumann, H.H., Nesic, Z., Staebler, R., Hartog, G. Den., Novak, M.D., Lee, X., 1997. Energy Balance and Canopy Conductance of a Boreal Aspen Forest: Partitioning Overstory and Understory Components. Journal of Geophysical Research 102 : 28915-28927 [ Links ]
Blanken, P.D., Black, T.A., Neumann, H.H., Hartog, G. Den, Yang, P.C., Nesic, Z., Staebler R., Chen, W., Novak, M.D., 1998. Turbulent Flux Measurements Above and Below the Overstorey of a Boreal Aspen Forest. Boundary Layer Meteorology 89 : 109-140 [ Links ]
Brunet, Y., 1999. Turbulence et Transport. Seminário sobre Transferências Hídricas em Cobertos Vegetais Descontínuos, Oeiras [ Links ]
Campbell, G.S., 1986. An Introduction to Environmental Biophysics. Springer Verlag [ Links ]
Carvalho J.S., 1985. Notas para o Curso de Formação de Técnicos para a Indústria da Cortiça. Instituto Superior Técnico - Estação Florestal Nacional [ Links ]
Denmead, O.T., Bradley, E.F., 1985. Flux-Gradient Relationships in a Forest Canopy. Em: The Forest-Atmosphere Interaction (ed. B.A Hutchinson e B.B. Hichs) pp. 421-442. Reidel Publishing Company [ Links ]
Foken, Th., Wichura, B., 1996. Tools for Quality Assessing of Surface-Based Flux Measurements. Agricultural and Forest Meteorology 78 : 83-105 [ Links ]
Fortes, M.A., 1989. A Cortiça. Colóquio Ciências N.4, Jan/Abr, 35-60 [ Links ]
Geiger, R., 1990. Manual de Microclimatologia - O Clima da Camada de Ar Junto ao Solo. Fundação Calouste Gulbenkian, 4ªEd. [ Links ]
Goes, E., 1991. A Floresta Portuguesa. Portucel [ Links ]
Incropera, F.P., Witt, D.P., 1990. Fundamentals of Heat and Mass Transfer. 3rd ed., John Wiley & Sons [ Links ]
Jaeger L., Kessler, A., 1997. Twenty Years of Heat and Water Balance Climatology at the Hartheim Pine Forest, Germany. Agricultural and Forest Meteorology 84 : 25-36 [ Links ]
Kaimal, J.C., Gaynor, J.E., 1991. Another Look at Sonic Thermometry, Boundary Layer Meteorology 56 : 401-410 [ Links ]
Kaimal, J.C., Finnigan, J.J., 1994. Atmospheric Boundary Layer Flows. Their Structure and Measurement. Oxford University Press [ Links ]
Lamaud, E., Ogée, J., Brunet, Y., Berbigier, P., 2001. Validation of Flux Measurements Above the Understorey of a Pine Forest. Agricultural and Forest Meteorology 106 : 187-203 [ Links ]
Laubach, J., Raschendorfer, M., Kreilein, H., Gravenhorst, G., 1994. Determination of Heat and Water Vapour Fluxes Above a Spruce Forest by Eddy Correlation. Agricultural and Forest Meteorology 71 : 373-401 [ Links ]
Laubach, J., McNaughton, K., 1998. A Spectrum-Independent Procedure for Correcting Eddy Fluxes Measured with Independent Sensors. Boundary Layer Meteorology 89 : 445-467 [ Links ]
Lee, X., Black, T.A., 1993a. Atmospheric Turbulence Within and Above a Douglas Fir Stand. Part I: Statistical Properties of the Velocity Field. Boundary Layer Meteorology 64 : 149-174 [ Links ]
Lee, X., Black, T.A., 1993b. Atmospheric Turbulence Within and Above a Douglas Fir Stand. Part II: Eddy Fluxes of Sensible Heat and Water Vapour. Boundary Layer Meteorology 64 : 369-389 [ Links ]
Lindroth, A., 1985. Seasonal and Diurnal Variation of Energy Budget Components in Coniferous Forests. Journal of Hydrology 82 : 1-15 [ Links ]
Mcaughey, J.H., 1985. A Radiation and Energy Balance Study of Mature Forest and Clear-Cut Sites. Boundary Layer Meteorology 32 : 1-24 [ Links ]
Mcaughey, J.H., Saxton, W.L., 1988. Energy Balance Storage Terms in a Mixed Forest. Agricultural and Forest Meteorology 44: 1-18 [ Links ]
Monteith, J.L., Unsworth, M.H., 1990. Principles of Environmental Physics. 2nd. Ed., Edward Arnold [ Links ]
Moore, C.J., Fisch, G., 1986. Estimating Heat Storage in Amazonian Tropical Forest. Agricultural and Forest Meteorology 38: 147-169 [ Links ]
Natividade, J.V., Subericultura. DGF [ Links ]
Ogée, J., Lamaud, E., Brunet, Y., Berbigier, P., Bonnefond, J.M., 2001. A long-term Study of Soil Heat Flux Under a Forest Canopy. Agricultural and Forest Meteorology 106 : 173-186 [ Links ]
Oke, T.R., 1992. Boundary Layer Climates. 2nd Edition, Routledge [ Links ]
Páscoa, F., Silva, R., 1986. Produto de Podas em Sobreiro: Tabelas de Biomassa, Em: 1ºEncontro sobre Montados de Sobro e Azinho (ed. Sociedade Portuguesa de Ciências Florestais, Liga para a Protecção da Natureza e Grupo Universitário de Évora de Estudos de Ambiente) [ Links ]
Rauner, J.L., 1976. Deciduous Forests. Em: Vegetation and Atmosphere, Vol. II (ed. J.L.Monteith) 241-264. Academic Press [ Links ]
Rodrigues, A.M., 2002. Fluxos de Momento, Massa e Energia na Camada Limite Atmosférica em Montado de Sobro, Dissertação para a obtenção do Grau de Doutor em Engenharia do Ambiente, Instituto Superior Técnico, Universidade Técnica de Lisboa [ Links ]
Sutton, O.G., 1953. Micrometeorology. McGraw-Hill [ Links ]
Tanner, B.D., Swiatek, E., Greene, J.P., 1993. Density Fluctuations and Use of the Krypton Hygrometer in Surface Flux Measurements. Em: Management of Irrigation and Drainage Systems. (Workshop of the Irrigation and Drainage Div./ASCE, July 21-23, Park City,Utah ) [ Links ]
Thom, A.S., 1975. Momentum, Mass and Heat Exchange of Plant Communities. Em: Vegetation and Atmosphere, Vol I (ed. J.L. Monteith) 57-109. Academic Press [ Links ]
Webb, E.K., Pearman, G.I., Leuning, R., 1980. Correction of Flux Measurements for Density Effects Due to Heat and Water Vapor Transfer. Quarterly Journal of the Royal Meteorological Society 106 : 85-100 [ Links ]
Valente, F.M.R.T., 1999. Intercepção da precipitação em povoamentos esparsos. Modelação do processo e características aerodinâmicas dos cobertos molhados. Tese de Doutoramento, Universidade Técnica de Lisboa, Instituto Superior de Agronomia, Lisboa [ Links ]
Vogt, R., Jaeger, L., 1990. Evaporation From a Pine Forest-Using the Aerodynamic Method and Bowen Ratio Method. Agriculture and ForestMeteorology 50 : 39-54 [ Links ]
Submetido para publicação em Fevereiro de 2003
Aceite para publicação em Março de 2003
1 E-mail: abel.rodrigues@efn.com.pt
]]>