Some Interesting Features of the Nocturnal Boundary Layer Above Caxiuanã Amazonian Rain Forest Using High Resolution Simulation
Nogueira, Universidade Federal do Pará - UFPA, email@example.com
Cohen, Universidade Federal do Pará - UFPA, firstname.lastname@example.org
Deane de Abreu
Sá, Centro de Previsão de Tempo e Estudos Climáticos, Instituto Nacional de Pesquisas Espaciais/Museu Paraense Emílio Goeldi, email@example.com
Gandu, Universidade de São Paulo - USP, firstname.lastname@example.org
Interesting characteristics of the nocturnal bondary-layer (NBL) above the Caxiuanã Forest, Pará, are investigated. Rawinsonde, cup anemometer and tower fast-response data obtained during dry season have been used. One of these characteristics is the existence, in some situations, of relative maxima in the wind velocity vertical profiles, the “low level jets” (LLJ), in regions less than 1 km distant from the surface. They may contribute to intensify the mixture in the surface and in the region where they occur. It is possible that the presence of such phenomenon introduce additional difficulties in the parameterization of forest-atmosphere exchange processes.
BRAMS (Brazilian developments on the Regional Atmospheric Modeling System) was used to evaluate the LLJ’s origin. Although the numerical simulations did reproduce the LLJs, they did not generate all the flow characteristics. The origin of the jets was revealed by the model to be associated to a phenomenon of canalization of the flow above a region of great rivers in the Northeast of Pará.
Another observed phenomenon is the wind gust. Turbulent series of wind velocity components, CO2 concentration, specific humidity and temperature, showed the importance of these episodes upon the variability patterns of the forest-atmosphere interaction. Like-ramp coherent structures were also observed during the wind gusts. Integration calculations have demonstrated that wind gusts are responsible for considerable parcels of the nocturnal total forest-atmosphere scalar exchanges, particularly in CO2 releasing.
These results are interesting to understand physical processes which stabilize NBL and probably generate favourable conditions for low level jets occurrence.