Giuliano Demarco

COMPARISON OF WIND DATA OF ERA-INTERIM REANALYSIS AND CFSR WITH THE DATA FROM AUTOMATIC INMET STATIONS IN RIO GRANDE DO SUL

Wind power is currently one of the sources of electricity the fastest growing worldwide. However, especially in Brazil, it is still very difficult to locate areas with reliable winds for the implementation of a wind farm, because there is not enough data density that guarante the wind farm efficiency. Thus, the development of models that simulate wind conditions are extremely important for studies and research in this area. In this way, weather reanalysis data can be used as input into high-resolution regional models, for example. Therefore, this work presents a study comparing two sets of weather Reanalysis of wind data - ERA-Interim and CFSR - with measured data from automated weather stations of the National Institute of Meteorology in the Rio Grande do Sul state in order to obtain the coefficient correlation of data from reanalysis with data measured for each measurement point and for every season. For better visualization of the correlation results, it is also built contour maps with correlation coefficient where can be seeing that the best performance of the CFSR reanalysis.

APPLICATION OF THE HILBERT-HUANG TRANSFORM IN VELOCITY DATA MEASURED IN WIND TUNNEL

In this study, the Hilbert-Huang transform was applied to experimental measurements performed in a wind tunnel to determine the frequency of occurrence of the spectral maximum. These maximum frequencies are associated with the time scale of the most energetic eddies and represent an important input parameter in the pollutants dispersion models. The values of the maximum frequencies obtained by the Hilbert-Huang marginal spectrum are compared with the vaues obtained by the traditionally used Fourier transform. The results show that the energy distribution calculated by both methods are very similar in the region of occurence of the spectral maximum, and for this reason, the maximum frequency values obtained by each method do not presente significant differences. Under determined hypothesis, the Hilbert-Huang transform provided physically more realistic maximum frequency values that those obtained using the Fourier transform.

The Influence of the Intermittent Behavior of the Nocturnal Atmospheric Flow on the Prediction of the Diurnal Temperature Range: A Simplified Model Analysis

The variation of the atmospheric temperature near the surface associated with anthropogenic effects is analyzed using a simplified atmospheric model. Local changes in cloud cover and four different scenarios of atmospheric concentration of carbon dioxide are considered. The results show that the highest temperature variability occurs in the weak wind and decoupled state and in the transition between flow regimes. In agreement with previous efforts, the results indicate that the reduction of diurnal temperature range is related to the existence of two distinct flow regimes in the stable boundary layer. However, in the decoupled state, the occurrence of intermittent bursts of turbulence may cause temperature variations among the different scenarios to become unpredictable. It implies that it is difficult to predict the diurnal temperature range in places where low winds are common.

Identification and Estimation of the Period of Non-Turbulent Oscillatory Processes in the Stable Boundary layer Through Autocorrelation Functions

The autocorrelation function of the flow speed components, measures the relationship that the speed in a certain instant, has with the speed at an earlier instant. In some conditions, in the atmospheric flow, this autocorrelation presents a low frequency oscillatory shape, presenting negative lobes. This behavior is known as meandering phenomenon and becomes prevalent in low wind conditions. The objective of this study is to compare the adjustments of autocorrelation functions, present in the literature, with trial of the experimental data of FLOOSS II experiment, for determining the meandering oscillation period. Initially, three selection criteria were used to select the windows of analysis. Among the criteria the magnitude of the wind showed the most satisfactory. The fitting curves showed that both autocorrelation functions performed well, even with a large variability of oscillation periods that were found. The great variability in the oscillation period of the meandering phenomena can be associated with the nature of the physical phenomenon that is responsible for its origin. However, this hypothesis needs confirmation.

ANALYSIS OF THE PROPAGATION AND MAINTENANCE OF VORTICES GENERATED BY A STATIC AND ISOLATED MICROBURST

The Southern Brazilian region is specially affected by extreme weather events, very often intense wind gusts coming from deep convection may develop itself as a microburst producing winds higher than 100 km/h. In order to understand the physical and dynamical process evolved in this phenomena, a static and isolated microburst is produced through a Large Eddy Simulation. A quantitative analysis of propagation an maintenance of the microburst vortex ring is performed in order to understand its evolution.

QUANTIFICAÇÃO DA INTERMITÊNCIA NA CAMADA LIMITE ESTÁVEL EM UM SÍTIO EXPERIMENTAL NA FLORESTA AMAZÔNICA

O proposito do presente trabalho e utilizar um metodo de determinacao de intermitencia e quantificar como esta afeta as series de temperatura e CO 2 . Tais analises sao feitas para um sitio especifico na regiao Amazonica.

DEPENDÊNCIA DA VARIABILIDADE LOCAL DA TEMPERATURA NOTURNA EM DIFERENTES CENÁRIOS DE CONCENTRAÇÃO DE CO2 COM O REGIME DE ESCOAMENTO ATMOSFÉRICO

Neste trabalho, e analisada a variacao da temperatura atmosferica proximo a superficie considerando quatro diferentes cenarios de concentracao atmosferica de dioxido de carbono. E mostrado que as maiores variabilidades de temperatura ocorrem no estado desconectado na regiao transicao entre os regimes. Os resultados indicam que a diminuicao na variacao de temperatura diurna pode estar associada a variabilidade de regimes na camada limite estavel.

ANÁLISE DA INFLUÊNCIA DA ESTRATIFICAÇÃO SOBRE PERFIS DE VENTO E TEMPERATURA EM EXPERIMENTOS DE TÚNEL DE VENTO

Este trabalho relata um escoamento estratificado e turbulento, no qual a superficie e mais fria que o ambiente sobre ela. Dessa forma, verifica-se a influencia da estratificacao sobre os perfis de vento e temperatura.

DEPENDÊNCIA DA TAXA DE DISSIPAÇÃO VISCOSA COM A ESTABILIDADE ATMOSFÉRICA EM CONDIÇÕES MUITO ESTÁVEIS

A descricao prognostica do escoamento turbulento na camada limite muito estavel e um desafio para modelos numericos, pois os mecanismos que mantem a atividade turbulenta sao desconhecidos. Neste trabalho, sao analisadas as implicacoes das hipoteses de Kolmogorov na parametrizacao da taxa de dissipacao viscosa. Os resultados indicam que esta deve depender do regime de escoamento atmosferico.