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<p>Observations of third-order moments associated with turbulent transport terms and of dissipation rate terms in the prognostic equations for turbulent kinetic energy, heat flux, and temperature variance are analyzed. Two months of high-frequency turbulence measurements at ten vertical levels of sonic anemometers deployed on a 30-m tower over a grassland site in southern Brazil have been used. This unique dataset allowed the investigation of the vertical structure of these terms and their dependence on wind speed and stability in the atmospheric surface layer under convective conditions. Results show that the magnitude of these terms increases systematically with wind speed at all levels. A variety of empirical formulations for the third-order moments and dissipation rates in terms of lower order moments and their vertical gradients are compared among each other. They are also compared with previously published parameterizations for the same quantities. The analysis indicates which expressions provide a more accurate representation of the observed data that is also independent of height. These formulations offer a practical and simplified alternative to existing approaches and are particularly suitable for implementation in higher-order closure models, where prognostic equations for budget terms are explicitly solved.</p>

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Turbulent Transports and Dissipation Rates in the Budget Equations for Second Order Moments in the Surface Convective Atmospheric Boundary Layer

  • 期刊论文

  • 发表日期：

    2026年2月5日

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  • Alessandro E. D. Pozzobon,
  • Michel Stefanello,
  • Otávio C. Acevedo,
  • Franciano S. Puhales,
  • Rafael Maroneze

摘要

Observations of third-order moments associated with turbulent transport terms and of dissipation rate terms in the prognostic equations for turbulent kinetic energy, heat flux, and temperature variance are analyzed. Two months of high-frequency turbulence measurements at ten vertical levels of sonic anemometers deployed on a 30-m tower over a grassland site in southern Brazil have been used. This unique dataset allowed the investigation of the vertical structure of these terms and their dependence on wind speed and stability in the atmospheric surface layer under convective conditions. Results show that the magnitude of these terms increases systematically with wind speed at all levels. A variety of empirical formulations for the third-order moments and dissipation rates in terms of lower order moments and their vertical gradients are compared among each other. They are also compared with previously published parameterizations for the same quantities. The analysis indicates which expressions provide a more accurate representation of the observed data that is also independent of height. These formulations offer a practical and simplified alternative to existing approaches and are particularly suitable for implementation in higher-order closure models, where prognostic equations for budget terms are explicitly solved.