Navegando por Assunto "Ventos"

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Acesso aberto (Open Access)
Aspectos observacionais e numéricos da interação floresta-atmosfera na Amazônia oriental: fenômenos turbulentos noturnos
(Universidade Federal do Pará, 2008) NOGUEIRA, Daniele Santos; GANDU, Adilson Wagner; http://lattes.cnpq.br/8491359374260645; SÁ, Leonardo Deane de Abreu; http://lattes.cnpq.br/0107976161469463
This study identified two nocturnal turbulent phenomena above Caxiuanã region, in the eastern Amazonia, during its dry season: low level jets (LLJ) and wind gusts, using data from the field campaigns CiMeLA (dry season of 2003) and COBRA-PARÁ (dry season of 2006). Both of them were analyzed observationally, considering aspects such as time of occurrence, intensity, height and duration, as well as their nocturnal evolution. It was verified that most of the LLJ events were accompanied by a drop in equivalent potential temperature. It was also found that the wind gusts had an important influence over the forest-atmosphere exchanges. The genesis of these phenomena was also investigated. It was noted, using the mesoscale model BRAMS, that the origin of the jets is possibly associated to the sea breeze and the intensification of the northeasterly winds. These results were based on sensibility tests, which included the removal of the rivers, the ocean-continent interface, the effects of downdrafts and the deforestation of the region. It was observed that the origin of the wind gusts is associated to the existence of Caxiuanã bay, which resembles a lake, and to the local convective activity. Furthermore, it was found that both phenomena did not exist simultaneously, except for one single night. This can be explained by a shear-sheltering effect that impedes that propagation of the turbulence downward, to the surface. This effect is generated by the presence of strong LLJs. This research reflects the importance and complexity of the atmospheric phenomena near the coast of Pará.
Acesso aberto (Open Access)
Influência da dinâmica atmosférica na produção de serapilheira em um manguezal da costa amazônica.
(Universidade Federal do Pará, 2019-02-19) SOUZA, Hyago Elias Nascimento; VITORINO, Maria Isabel; http://lattes.cnpq.br/2313369423727020
This work aimed to investigate the influence of atmospheric dynamics on litterfall production in the Cuiarana mangrove, Salinópolis, Amazon Coast. The seasonal rainfall variation was analyzed along with the precipitating systems on the Amazon coast and its influence on the variability of litterfall production. It was also characterized the temporal variation of the direction and speed of the wind and its influence on the spatiotemporal production of litterfall. In a mangrove forest, 3 sample plots were delineated with 3 mangrove species Rizophora mangle, Avicennia germinans and Laguncularia racemosa. In each plot, 4 traps 1 m2 were randomly installed. Meteorological data were obtained from the Micrometeorological Tower of the UFRA located in the study area. The main statistical methodologies used were two-way and one-way ANOVA, linear regression analysis (p <0.05) and Principal Components Analysis (PCA). The results show that the temporal variation of precipitation is modulated by different meteorological systems, where the months of March, April and May appear as the region's rainiest quarter. The annual distribution of wind direction showed predominance in the eastern (E), frequency of winds with higher velocity were recorded in the second semester. In the litterfall production there was a significant difference between the values of monthly production and between the fractions. The annual total litter production was 9.4 ± 0.06 Mg ha-1 year-1, where 67% was composed by the leaf fraction. Leaves had negative trends with precipitation, but woody and reproductive material had positive trends. The ACP shows in 4 components negative correlation with reproductive material and positive correlation with wood associated with the temporal variation of winds and rainfall.
Acesso aberto (Open Access)
Insights of meso and micro-scale processes for the Caxiuanã forest region from high resolution simulation
(2012-07) MESQUITA, Renata Leitão da Conceição; SILVA, Renato Ramos da
Meteorological data and high resolution numerical simulations were used to estimate spatial fields in eastern Amazonia where is located the Forest and the Bay of Caxiuanã. The study were performed for the period of November 2006, when occurred the field experiment COBRA-PARA. Analysis of the MODIS sensor from the Terra Satellite images show the occurrence of various phenomena such as local cloud streets, precipitating convective systems and an important influence of the interfaces between the forest and water surfaces. Numerical simulations for November 7, 2006 showed that the model represented well the major meteorological processes. The results show that the Caxiuanã Bay causes significant impact on adjacent meteorological fields mainly through advection by the northeast winds that induce to colder canopy temperature to the west of the bay and convective rainfall. Simulations with high resolution (LES) produced spatial patterns of temperature and humidity aligned with the winds during the daytime, and at nighttime the patterns are influenced mainly by the presence of the bay. Correlations between the mid-level winds and the latent heat fluxes showed that there is a change from negative correlations for the early hours to positive correlations for the afternoon and early evening.