A Local Similarity Function for Katabatic Flows Derived From Field Observations Over Steep‐ and Shallow‐Angled Slopes

Hang, Chaoxun; Oldroyd, H. J.; Giometto, M. G.; Pardyjak, Eric R.; Parlange, Marc B.

doi:10.1029/2021gl095479

Cited by 4 publications

(1 citation statement)

References 57 publications

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“…However, all models are approximations of reality. In the future, we plan to improve this model by incorporating the advection effects of local inhomogeneities at the surface (e.g., for relatively small lakes surrounded by desiccated land), including precipitation fluxes, and modeling the effects of steep slopes that can generate katabatic winds at the surface (e.g., Chapter 7 of Brutsaert, 1982; Radić et al., 2017; Spiga & Smith, 2018; Hang et al., 2021).…”

Section: Summary and Future Workmentioning

confidence: 99%

Turbulent Fluxes and Evaporation/Sublimation Rates on Earth, Mars, Titan, and Exoplanets

Khuller,

Clow

2024

JGR Planets

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Turbulent fluxes of heat, momentum, and humidity in the atmospheric boundary layer are pivotal to the evolution of geology, weather and climate, and the possibility of life. Here we extend recent advances in calculating these near‐surface turbulent fluxes in the Earth's atmospheric boundary layer to any terrestrial planetary body with an atmosphere. These improvements include: (a) incorporating Monin‐Obukhov similarity functions that encompass the entire range of atmospheric stability expected on terrestrial planetary bodies, (b) accounting for the additional shear associated with buoyant plumes under unstable conditions, (c) using surface renewal theory to calculate transfer rates within the interfacial layer adjacent to the surface, and (d) explicitly accounting for key humidity effects that become especially important when a volatile is more buoyant than the ambient gas (e.g., on Mars where H2O is lighter than CO2). We tested and validated our model using in situ data collected on Earth, Mars, and Titan under a wide range of atmospheric stability, pressure, and surface roughness conditions. The model shows up to 71% better agreement with measurements compared to methods commonly used on Mars for evaporation/sublimation. Compared to previous estimates for H2O ice on Mars, our model predicts up to 1.5–190x lower latent heat fluxes under stable atmospheric conditions (depending on the wind speed) and 1.78x higher latent heat fluxes under unstable conditions. Our results provide improved constraints on the stability of ice on Mars and will help determine whether ice can melt under present‐day conditions.

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Section: Summary and Future Workmentioning

confidence: 99%

Turbulent Fluxes and Evaporation/Sublimation Rates on Earth, Mars, Titan, and Exoplanets

Khuller,

Clow

2024

JGR Planets

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Flux‐gradient relations and their dependence on turbulence anisotropy

Mosso,

Calaf,

Stiperski

2024

Quart J Royal Meteoro Soc

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Monin–Obukhov similarity theory (MOST) is used in virtually all Earth System Models to parametrize the near‐surface turbulent exchanges and mean variable profiles. Despite its widespread use, there is high uncertainty in the literature about the appropriate parametrizations to use. In addition, MOST has limitations in very stable and unstable regimes, over heterogeneous terrain and complex orography, and has been found to represent the surface fluxes incorrectly. A new approach including turbulence anisotropy as a non‐dimensional scaling parameter has recently been developed and has been shown to overcome these limitations and generalize the flux‐variance relations to complex terrain. In this article, we analyze the flux‐gradient relations for five well‐known datasets, ranging from flat and homogeneous to slightly complex terrain. The scaling relations show substantial scatter and highlight the uncertainty in the choice of parametrization even over canonical conditions. We show that, by including information on turbulence anisotropy as an additional scaling parameter, the original scatter becomes well bounded and new formulations can be developed that drastically improve the accuracy of the flux‐gradient relations for wind shear () in unstable conditions and for temperature gradient () in both unstable and stable regimes. This analysis shows that both and are strongly dependent on turbulence anisotropy and allows us finally to settle the extensively discussed free convection regime for , which clearly exhibits a power law when anisotropy is accounted for. Furthermore, we show that the eddy diffusivities for momentum and heat and the turbulent Prandtl number are strongly dependent on anisotropy and that the latter goes to zero in the free convection limit. These results highlight the necessity to include anisotropy in the study of near‐surface atmospheric turbulence and lead the way for theoretically more robust simulations of the boundary layer over complex terrain.

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Understanding Thermally Driven Slope Winds: Recent Advances and Open Questions

Farina,

Zardi

2023

Boundary-Layer Meteorol

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The paper reviews recent advances in our understanding about the dynamics of thermally driven winds over sloping terrain. Major progress from recent experiments, both in the field and in the laboratory, are outlined. Achievements from numerical modelling efforts, including both parameterized turbulence and large eddy simulation approaches, up to direct numerical simulations, are also reviewed. Finally, theoretical insights on the nature of turbulence in such winds are analyzed along with applications which benefit from progress in understanding of these flows. Open questions to be faced for further investigations are finally highlighted.

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A Local Similarity Function for Katabatic Flows Derived From Field Observations Over Steep‐ and Shallow‐Angled Slopes

Cited by 4 publications

References 57 publications

Turbulent Fluxes and Evaporation/Sublimation Rates on Earth, Mars, Titan, and Exoplanets

Turbulent Fluxes and Evaporation/Sublimation Rates on Earth, Mars, Titan, and Exoplanets

Flux‐gradient relations and their dependence on turbulence anisotropy

Understanding Thermally Driven Slope Winds: Recent Advances and Open Questions

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