Unified Entrainment and Detrainment Closures for Extended Eddy‐Diffusivity Mass‐Flux Schemes
Abstract We demonstrate that an extended eddy‐diffusivity mass‐flux (EDMF) scheme can be used as a unified parameterization of subgrid‐scale turbulence and convection across a range of dynamical regimes, from dry convective boundary layers, through shallow convection, to deep convection. Central to...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
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American Geophysical Union (AGU)
2020-09-01
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| Series: | Journal of Advances in Modeling Earth Systems |
| Subjects: | |
| Online Access: | https://doi.org/10.1029/2020MS002162 |
| _version_ | 1818590926584414208 |
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| author | Yair Cohen Ignacio Lopez‐Gomez Anna Jaruga Jia He Colleen M. Kaul Tapio Schneider |
| author_facet | Yair Cohen Ignacio Lopez‐Gomez Anna Jaruga Jia He Colleen M. Kaul Tapio Schneider |
| author_sort | Yair Cohen |
| collection | DOAJ |
| description | Abstract We demonstrate that an extended eddy‐diffusivity mass‐flux (EDMF) scheme can be used as a unified parameterization of subgrid‐scale turbulence and convection across a range of dynamical regimes, from dry convective boundary layers, through shallow convection, to deep convection. Central to achieving this unified representation of subgrid‐scale motions are entrainment and detrainment closures. We model entrainment and detrainment rates as a combination of turbulent and dynamical processes. Turbulent entrainment/detrainment is represented as downgradient diffusion between plumes and their environment. Dynamical entrainment/detrainment is proportional to a ratio of a relative buoyancy of a plume and a vertical velocity scale, that is modulated by heuristic nondimensional functions which represent their relative magnitudes and the enhanced detrainment due to evaporation from clouds in drier environment. We first evaluate the closures offline against entrainment and detrainment rates diagnosed from large‐eddy simulations (LES) in which tracers are used to identify plumes, their turbulent environment, and mass and tracer exchanges between them. The LES are of canonical test cases of a dry convective boundary layer, shallow convection, and deep convection, thus spanning a broad range of regimes. We then compare the LES with the full EDMF scheme, including the new closures, in a single column model (SCM). The results show good agreement between the SCM and LES in quantities that are key for climate models, including thermodynamic profiles, cloud liquid water profiles, and profiles of higher moments of turbulent statistics. The SCM also captures well the diurnal cycle of convection and the onset of precipitation. |
| first_indexed | 2024-12-16T10:04:18Z |
| format | Article |
| id | doaj.art-2de128972ff244e0bfb43e848195377c |
| institution | Directory Open Access Journal |
| issn | 1942-2466 |
| language | English |
| last_indexed | 2024-12-16T10:04:18Z |
| publishDate | 2020-09-01 |
| publisher | American Geophysical Union (AGU) |
| record_format | Article |
| series | Journal of Advances in Modeling Earth Systems |
| spelling | doaj.art-2de128972ff244e0bfb43e848195377c2022-12-21T22:35:42ZengAmerican Geophysical Union (AGU)Journal of Advances in Modeling Earth Systems1942-24662020-09-01129n/an/a10.1029/2020MS002162Unified Entrainment and Detrainment Closures for Extended Eddy‐Diffusivity Mass‐Flux SchemesYair Cohen0Ignacio Lopez‐Gomez1Anna Jaruga2Jia He3Colleen M. Kaul4Tapio Schneider5Department of Environmental Science and Engineering California Institute of Technology Pasadena CA USADepartment of Environmental Science and Engineering California Institute of Technology Pasadena CA USADepartment of Environmental Science and Engineering California Institute of Technology Pasadena CA USADepartment of Environmental Science and Engineering California Institute of Technology Pasadena CA USAPacific Northwest National Laboratory Richland WA USADepartment of Environmental Science and Engineering California Institute of Technology Pasadena CA USAAbstract We demonstrate that an extended eddy‐diffusivity mass‐flux (EDMF) scheme can be used as a unified parameterization of subgrid‐scale turbulence and convection across a range of dynamical regimes, from dry convective boundary layers, through shallow convection, to deep convection. Central to achieving this unified representation of subgrid‐scale motions are entrainment and detrainment closures. We model entrainment and detrainment rates as a combination of turbulent and dynamical processes. Turbulent entrainment/detrainment is represented as downgradient diffusion between plumes and their environment. Dynamical entrainment/detrainment is proportional to a ratio of a relative buoyancy of a plume and a vertical velocity scale, that is modulated by heuristic nondimensional functions which represent their relative magnitudes and the enhanced detrainment due to evaporation from clouds in drier environment. We first evaluate the closures offline against entrainment and detrainment rates diagnosed from large‐eddy simulations (LES) in which tracers are used to identify plumes, their turbulent environment, and mass and tracer exchanges between them. The LES are of canonical test cases of a dry convective boundary layer, shallow convection, and deep convection, thus spanning a broad range of regimes. We then compare the LES with the full EDMF scheme, including the new closures, in a single column model (SCM). The results show good agreement between the SCM and LES in quantities that are key for climate models, including thermodynamic profiles, cloud liquid water profiles, and profiles of higher moments of turbulent statistics. The SCM also captures well the diurnal cycle of convection and the onset of precipitation.https://doi.org/10.1029/2020MS002162unified parameterizationconvective parameterizationeddy‐diffusivity mass‐flux parameterizationentrainment and detrainmentdeep convectionclimate modeling |
| spellingShingle | Yair Cohen Ignacio Lopez‐Gomez Anna Jaruga Jia He Colleen M. Kaul Tapio Schneider Unified Entrainment and Detrainment Closures for Extended Eddy‐Diffusivity Mass‐Flux Schemes Journal of Advances in Modeling Earth Systems unified parameterization convective parameterization eddy‐diffusivity mass‐flux parameterization entrainment and detrainment deep convection climate modeling |
| title | Unified Entrainment and Detrainment Closures for Extended Eddy‐Diffusivity Mass‐Flux Schemes |
| title_full | Unified Entrainment and Detrainment Closures for Extended Eddy‐Diffusivity Mass‐Flux Schemes |
| title_fullStr | Unified Entrainment and Detrainment Closures for Extended Eddy‐Diffusivity Mass‐Flux Schemes |
| title_full_unstemmed | Unified Entrainment and Detrainment Closures for Extended Eddy‐Diffusivity Mass‐Flux Schemes |
| title_short | Unified Entrainment and Detrainment Closures for Extended Eddy‐Diffusivity Mass‐Flux Schemes |
| title_sort | unified entrainment and detrainment closures for extended eddy diffusivity mass flux schemes |
| topic | unified parameterization convective parameterization eddy‐diffusivity mass‐flux parameterization entrainment and detrainment deep convection climate modeling |
| url | https://doi.org/10.1029/2020MS002162 |
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