Dissertações em Ciências Ambientais (Mestrado) - PPGCA/IG

URI Permanente para esta coleçãohttps://repositorio.ufpa.br/handle/2011/2855

O Mestrado Acadêmico em Ciências Ambientais teve início em 2005 e funciona no Programa de Pós-Graduação em Ciências Ambientais (PPGCA) do Instituto de Geociências (IG) da Universidade Federal do Pará (UFPA) em parceria com o Museu Paraense Emílio Goeldi (MPEG) e a Empresa Brasileira de Pesquisa Agropecuária (EMBRAPA/Amazônia Oriental).

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    Estudo comparativo da estrutura da turbulência atmosférica na camada limite superficial acima da floresta primária e região desmatada da Amazônia: análise de ondeletas aplicadas à detecção de estruturas correntes
    (Universidade Federal do Pará, 2008) DIAS JÚNIOR, Cléo Quaresma; MARQUES FILHO, Edson Pereira; http://lattes.cnpq.br/3112476528507003; SÁ, Leonardo Deane de Abreu; http://lattes.cnpq.br/0107976161469463
    Fast response turbulent data measured in micrometeorological towers located at the Caxiuanã Reserve, PA, (54m height), the Rebio-Jaru, RO, (60m height) and the Fazenda Nossa Senhora, RO, (4,04m height) have been analysed. A comparative study of coherent structures detection above experimental sites with distinct roughness surface conditions, forest and pasture, has been performed. The wavelet of Morlet has been used to identify the occurrence scale of coherent structures in temperature series data. Mean time and space scales of the coherent structures above two surfaces with different surface roughnesses have bean compared: for Caxiuanã and Fazenda Nossa Senhora experimental sites. Atmospheric stability parameters have been calculated to provide information to study the variability of coherent structures and its relationship with atmospheric stability conditions. For the Rebio-Jaru experimental site, the inflexional point height concerning the mean wind velocity vertical profile above and inside the forest canopy has been to determined, too. Finally, to better understand the earlier findings regarding turbulent mixing coherent structures characteristics, correlation coefficients between the vertical velocity and temperature time series have been calculated: a) for the measured data; b) for the wavelet coefficients on the time-scale of coherent structures occurrence. The results have shown clear differences between coherent structures occurrence scales above rough surfaces, as forestas, and smoother surfaces, as pastures. Above forest, under near neutral conditions, oscillation patterns with 80s time-scale are dominant, probably associated with “like rolls” structures. However, lesser was the inflexional point height of the wind profile, lesser was the coherent structures time-scale, probably as a consequence of the greater dissipation effect resulting of the impact action of the canopy physical structure upon the flow turbulent eddies. Further, correlation coefficients between the vertical velocity and the temperature calculated from the wavelet coefficients on the timescale of coherent structures occurrence are clearly greater than the ones resulting of the measured data (all available time-scales). Overall, the results suggest that there are crucial changes in the turbulence structure of the flows above deforested regions comparatively with the ones above pristine forest in Amazonia.
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