Similarity between heat and water vapor turbulent transport in the Atmospheric Surface Layer has been the basis of many engineering models to calculate surface fluxes, including the widely applied Bowen ratio equation, for a long time. Modernly, it is best understood within the context of Monin‐Obkhov Similarity Theory (MOST). In this work we study similarity between temperature and humidity, the Bowen ratio, and turbulent mass and heat transfer coefficients over a tropical lake in Brazil (Furnas Lake). The analysis was partly based on the concept of ‘Surface flux numbers’ recently proposed to diagnose scalar similarity, and considered wind directions and flux footprints. A period of 50 days of 30‐min. micrometeorological runs was used. Several cases of dissimilar temperature‐humidity behavior were found in the data. Both footprint extent and an aggregate temperature‐humidity Surface flux number turned out to be insufficient to diagnose these situations, but separate flux numbers for each scalar were able to diagnose their individual conformity to MOST. Overall, temperature displayed consistently larger relative variances and fluxes in comparison with humidity. The results highlight the need of careful analysis when measurements are made at sites close to land, when flux footprints may extend over there, indicating the possibility of advection effects. Copyright © 2016 John Wiley & Sons, Ltd.

This paper presents an evaluation of scalar similarity and scalar flux similarity of measurements above the water surface of the Itaipu hydroelectric reservoir. The scalars studied were: CO2 mixing ratio (rc), air temperature (θ), specific air humidity (q) and the vertical wind velocity (w). With the variance method it was found that the vertical wind velocity is in agreement with Monin-Obukhov Similarity Theory. On the other hand, the other scalars presented larger deviations in relation to the theoretical prediction. The worst results were for air temperature and mixing ratio of CO2. The most similar scalars were θ and q, with the most frequent correlation coefficient varying in the range [0.55:0.64] for measurements in unstable atmospheric conditions and in the [−0.85:−0.75] range for measurements under stable atmospheric conditions. Regarding the scalar fluxes, they presented greater similarity to each other than the scalars themselves.

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Resumo Este trabalho implementa um modelo de transferência entre superfície-vegetação-atmosfera para estimar os fluxos de calor sensível e latente, entre outras variáveis, em culturas agrícolas e outras coberturas vegetais. Foram feitas duas implementações distintas para o de resposta estomática das plantas. Estas implementações foram comparadas entre si e com medições de fluxo de calor latente e sensível em uma plantação de soja. Os resultados mostram o impacto das implementações de resposta estomática nos fluxos de calor latente e sensível, e que o modelo possui potencial de aplicações do modelo para previsões operacionais ou para simular cenários de modificações no uso do solo e possíveis mudanças climáticas decorrentes.