A new theoretical model for the spectra of turbulent kinetic energy which includes a proposal for the divergence of spectral energy

The paper solves the spectral equation of turbulent kinetic energy for a steady-state and stable horizontally homogeneous flow. Differently from latter approach it explicitly considers a model for the divergence of spectral energy due to pressure fluctuations. Using Green’s function it is postulated that this divergence is a linear combination of the other terms of the spectral equation. Physically acceptable results indicate that it can be dependent only on the second and third derivatives of the spectrum function. The model’s results show good agreement with previous studies as well as clear dependence with stability parameters according to the observations done by Kaimal et al

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Screenshot of our first portal showing the results of the supervisor software of the telemetric tests with a meteorological measurements tower.</p

Derivation of an eddy diffusivity coefficient depending on source distance for a shear dominated planetary boundary layer

AbstractIn this study an integral and an algebraic formulation for the eddy diffusivities in a shear driven planetary boundary layer are derived for pollutant dispersion applications. The expressions depend on the turbulence properties and on the distance from the source. They are based on the turbulent kinetic energy spectra, Taylor’s statistical diffusion theory and measured turbulent characteristics during intense wind events. The good agreement between the algebraic and the integral formulation for the eddy diffusivities corroborate the hypothesis that using an algebraic formulation as a surrogate for the eddy diffusivities in the neutral planetary boundary layer is valid. As a consequence, the vertical eddy diffusivity provided by the algebraic formulation and its asymptotic limit for large time (diffusion time much larger than the Lagrangian integral time scale), were introduced into an analytical air pollution model and validated against data from the classic Prairie Grass project. A statistical analysis, employing specific indices shows that the results are in good agreement with the observations. Furthermore, this study suggests that the inclusion of the memory effect, which is important in regions near to a continuous point source, improves the description of the turbulent transport process of atmospheric contaminants. Therefore, the major finding of this paper is the necessity of including the downwind distance-dependent eddy diffusivity for low continuous point sources in air quality modeling studies

Análise de Variáveis Atmosféricas Observadas em Alta Resolução Espaço-Temporal Durante um Experimento de 30 Dias na Mesorregião da Ilha de Santa Catarina

Resumo Campanhas meteorológicas são importantes porque revelam características atmosféricas não observadas rotineiramente. Entre julho e agosto de 2013, foi realizada uma campanha de 30 dias na Mesorregião da Ilha de Santa Catarina (MISC) que permitiu a construção de um banco de dados inédito, com observações a cada minuto em quatro locais estratégicos. O presente artigo aborda aspectos observacionais da micro e mesoescala a partir da utilização dos dados obtidos na referida campanha. Para explorar detalhadamente o comportamento das variáveis atmosféricas na MISC, estuda-se um caso de mudança brusca na direção do vento e dois casos em que foram observados os valores extremos na série de dados de temperatura utilizada. Os resultados mostram que a velocidade do vento é maior no oeste e sul e que a temperatura é menor no norte da MISC. A variação da temperatura a cada minuto é controlada essencialmente pela turbulência e pelas características das massas de ar transportadas no sentido do ponto de observação. Além disso, constatou-se que a variabilidade temporal da temperatura e umidade específica é similar em toda MISC a partir do momento que as forçantes atmosféricas com escala temporal de 1 h a 3 h passam a ser desprezíveis