scholarly journals An Eddy‐Diffusivity Mass‐Flux Parameterization for Modeling Oceanic Convection

2020 ◽  
Vol 12 (9) ◽  
Author(s):  
Hervé Giordani ◽  
Romain Bourdallé‐Badie ◽  
Gurvan Madec
Keyword(s):  
Mass Flux ◽  
Eddy Diffusivity ◽  
Flux Parameterization ◽  
Oceanic Convection

Improving the Representation of Subtropical Boundary Layer Clouds in the NASA GEOS Model with the Eddy-Diffusivity/Mass-Flux Parameterization

2021 ◽  
Vol 149 (3) ◽  
pp. 793-809
Author(s):  
Kay Suselj ◽  
Joao Teixeira ◽  
Marcin J. Kurowski ◽  
Andrea Molod
Keyword(s):  
Boundary Layer ◽  
Mass Flux ◽  
Eddy Diffusivity ◽  
Reanalysis Data ◽  
Cumulus Clouds ◽  
Boundary Layer Clouds ◽  
Stratocumulus Clouds ◽  
Pbl Scheme ◽  
Flux Parameterization ◽  
Flux Model

AbstractA systematic underestimation of subtropical planetary boundary layer (PBL) stratocumulus clouds by the GEOS model has been significantly improved by a new eddy-diffusivity/mass-flux (EDMF) parameterization. The EDMF parameterization represents the subgrid-scale transport in the dry and moist parts of the PBL in a unified manner and it combines an adjusted eddy-diffusivity PBL scheme from GEOS with a stochastic multiplume mass-flux model. The new EDMF version of the GEOS model is first compared against the CONTROL version in a single-column model (SCM) framework for two benchmark cases representing subtropical stratocumulus and shallow cumulus clouds, and validated against large-eddy simulations. Global simulations are performed and compared against observations and reanalysis data. The results show that the EDMF version of the GEOS model produces more realistic subtropical PBL clouds. The EDMF improvements first detected in the SCM framework translate into similar improvements of the global GEOS model.

scholarly journals Implementation of a Stochastic Eddy-Diffusivity/Mass-Flux Parameterization into the Navy Global Environmental Model

2014 ◽  
Vol 29 (6) ◽  
pp. 1374-1390 ◽  
Author(s):  
Kay Sušelj ◽  
Timothy F. Hogan ◽  
João Teixeira
Keyword(s):  
Boundary Layer ◽  
Mass Flux ◽  
Weather Forecasting ◽  
Eddy Diffusivity ◽  
Shallow Convection ◽  
Environmental Model ◽  
Eddy Simulation ◽  
Global Environmental ◽  
Current Implementation ◽  
Flux Parameterization

Abstract A unified boundary layer and shallow convection parameterization based on a stochastic eddy-diffusivity/mass-flux (EDMF) approach is implemented and tested in the Navy Global Environmental Model (NAVGEM). The primary goals of this work are to improve the representation of convectively driven boundary layers and the coupling between the boundary layer and cumulus regions. Within the EDMF framework the subgrid vertical fluxes are calculated as a sum of an eddy-diffusivity part, which in the current implementation is based on the approach developed by Louis in the late 1970s, and a stochastic mass-flux parameterization. The mass-flux parameterization is a model for both dry and moist convective thermals. Dry thermals, which represent surface-forced coherent structures in a flow, provide countergradient mixing in the boundary layer and, if conditions permit, are the roots for moist thermals. Moist thermals represent shallow convective clouds. The new parameterization implemented in a single-column model (SCM) version of NAVGEM is shown to be able to realistically simulate a variety of dry and moist convective cases. The NAVGEM SCM results are validated against large-eddy-simulation results. The skill of NAVGEM as a global weather forecasting model is considerably improved with the new EDMF parameterization. The EDMF parameterization became part of the operational NAVGEM in November 2013.

scholarly journals Unified Entrainment and Detrainment Closures for Extended Eddy-Diffusivity Mass-Flux Schemes

2020 ◽  
Author(s):  
Yair Cohen ◽  
Ignacio Lopez-Gomez ◽  
Anna Jaruga ◽  
Jia He ◽  
Colleen Kaul ◽  
...  
Keyword(s):  
Mass Flux ◽  
Eddy Diffusivity

scholarly journals An Improved Perturbation Pressure Closure for Eddy-Diffusivity Mass-Flux Schemes

2020 ◽  
Author(s):  
Jia He ◽  
Yair Cohen ◽  
Ignacio Lopez-Gomez ◽  
Anna Jaruga ◽  
Tapio Schneider
Keyword(s):  
Mass Flux ◽  
Eddy Diffusivity ◽  
Perturbation Pressure

scholarly journals Investigating the Scale Adaptivity of a Size-Filtered Mass Flux Parameterization in the Gray Zone of Shallow Cumulus Convection

2018 ◽  
Vol 75 (4) ◽  
pp. 1195-1214 ◽  
Author(s):  
Maren Brast ◽  
Vera Schemann ◽  
Roel A. J. Neggers
Keyword(s):  
Mass Flux ◽  
Turbulent Transport ◽  
Eddy Diffusivity ◽  
Coarse Grained ◽  
Parameterization Scheme ◽  
Quasi Equilibrium ◽  
Gray Zone ◽  
Cumulus Clouds ◽  
Eddy Simulation ◽  
Shallow Cumulus

Abstract In this study, the scale adaptivity of a new parameterization scheme for shallow cumulus clouds in the gray zone is investigated. The eddy diffusivity/multiple mass flux [ED(MF)n] scheme is a bin-macrophysics scheme in which subgrid transport is formulated in terms of discretized size densities. While scale adaptivity in the ED component is achieved using a pragmatic blending approach, the MF component is filtered such that only the transport by plumes smaller than the grid size is maintained. For testing, ED(MF)n is implemented into a large-eddy simulation (LES) model, replacing the original subgrid scheme for turbulent transport. LES thus plays the role of a nonhydrostatic testing ground, which can be run at different resolutions to study the behavior of the parameterization scheme in the boundary layer gray zone. In this range, convective cumulus clouds are partially resolved. The authors find that for quasi-equilibrium marine subtropical conditions at high resolutions, the clouds and the turbulent transport are predominantly resolved by the LES. This partitioning changes toward coarser resolutions, with the representation of shallow cumulus clouds gradually becoming completely carried by the ED(MF)n. The way the partitioning changes with grid spacing matches the behavior diagnosed in coarse-grained LES fields, suggesting that some scale adaptivity is captured. Sensitivity studies show that the scale adaptivity of the ED closure is important and that the location of the gray zone is found to be moderately sensitive to some model constants.

scholarly journals A Novel Framework for Evaluating and Improving Parameterized Subtropical Marine Boundary Layer Cloudiness

2019 ◽  
Vol 147 (9) ◽  
pp. 3241-3260 ◽  
Author(s):  
Mark Smalley ◽  
Kay Sušelj ◽  
Matthew Lebsock ◽  
Joao Teixeira
Keyword(s):  
Boundary Layer ◽  
Los Angeles ◽  
Mass Flux ◽  
Marine Boundary Layer ◽  
Probability Distributions ◽  
Joint Probability ◽  
Eddy Diffusivity ◽  
Liquid Water Path ◽  
Mixing Processes ◽  
Lower Tropospheric Stability

AbstractA single-column model (SCM) is used to simulate a variety of environmental conditions between Los Angeles, California, and Hawaii in order to identify physical elements of parameterizations that are required to reproduce the observed behavior of marine boundary layer (MBL) cloudiness. The SCM is composed of the JPL eddy-diffusivity/mass-flux (EDMF) mixing formulation and the RRTMG radiation model. Model forcings are provided by the Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA2). Simulated low cloud cover (LCC), rain rate, albedo, and liquid water path are compared to collocated pixel-level observations from A-Train satellites. This framework ensures that the JPL EDMF is able to simulate a continuum of real-world conditions. First, the JPL EDMF is shown to reproduce the observed mean LCC as a function of lower-tropospheric stability. Joint probability distributions of lower-tropospheric cloud fraction, height, and lower-tropospheric stability (LTS) show that the JPL EDMF improves upon its MERRA2 input but struggles to match the frequency of observed intermediate-range LCC. We then illustrate the physical roles of plume lateral entrainment and eddy-diffusivity mixing length in producing a realistic behavior of LCC as a function of LTS. In low-LTS conditions, LCC is mostly sensitive to the ability of convection to mix moist air out of the MBL. In high-LTS conditions, LCC is also sensitive to the turbulent mixing of free-tropospheric air into the MBL. In the intermediate LTS regime typical of stratocumulus–cumulus transition there is proportional sensitivity to both mixing mechanisms, emphasizing the utility of a combined eddy-diffusivity/mass-flux approach for representing mixing processes.

An eddy-diffusivity/mass-flux parametrization for dry and shallow cumulus convection

2004 ◽  
Vol 130 (604) ◽  
pp. 3365-3383 ◽  
Author(s):  
P.M.M. Soares ◽  
P.M.A. Miranda ◽  
A.P. Siebesma ◽  
J. Teixeira
Keyword(s):  
Mass Flux ◽  
Eddy Diffusivity ◽  
Cumulus Convection ◽  
Shallow Cumulus

scholarly journals Evaluation of PBL Parameterizations in WRF at Subkilometer Grid Spacings: Turbulence Statistics in the Dry Convective Boundary Layer

2016 ◽  
Vol 144 (3) ◽  
pp. 1161-1177 ◽  
Author(s):  
Hyeyum Hailey Shin ◽  
Jimy Dudhia
Keyword(s):  
Boundary Layer ◽  
Mass Flux ◽  
Weather Prediction ◽  
Wrf Model ◽  
Eddy Diffusivity ◽  
Weather Research And Forecasting ◽  
Turbulence Statistics ◽  
Convective Boundary ◽  
Large Eddies ◽  
Horizontal Grid

Abstract Planetary boundary layer (PBL) parameterizations in mesoscale models have been developed for horizontal resolutions that cannot resolve any turbulence in the PBL, and evaluation of these parameterizations has been focused on profiles of mean and parameterized flux. Meanwhile, the recent increase in computing power has been allowing numerical weather prediction (NWP) at horizontal grid spacings finer than 1 km, at which kilometer-scale large eddies in the convective PBL are partly resolvable. This study evaluates the performance of convective PBL parameterizations in the Weather Research and Forecasting (WRF) Model at subkilometer grid spacings. The evaluation focuses on resolved turbulence statistics, considering expectations for improvement in the resolved fields by using the fine meshes. The parameterizations include four nonlocal schemes—Yonsei University (YSU), asymmetric convective model 2 (ACM2), eddy diffusivity mass flux (EDMF), and total energy mass flux (TEMF)—and one local scheme, the Mellor–Yamada–Nakanishi–Niino (MYNN) level-2.5 model. Key findings are as follows: 1) None of the PBL schemes is scale-aware. Instead, each has its own best performing resolution in parameterizing subgrid-scale (SGS) vertical transport and resolving eddies, and the resolution appears to be different between heat and momentum. 2) All the selected schemes reproduce total vertical heat transport well, as resolved transport compensates differences of the parameterized SGS transport from the reference SGS transport. This interaction between the resolved and SGS parts is not found in momentum. 3) Those schemes that more accurately reproduce one feature (e.g., thermodynamic transport, momentum transport, energy spectrum, or probability density function of resolved vertical velocity) do not necessarily perform well for other aspects.

scholarly journals A Dual Mass Flux Framework for Boundary Layer Convection. Part II: Clouds

2009 ◽  
Vol 66 (6) ◽  
pp. 1489-1506 ◽  
Author(s):  
Roel A. J. Neggers
Keyword(s):  
Boundary Layer ◽  
Mass Flux ◽  
Cloud Model ◽  
Turbulent Transport ◽  
Eddy Diffusivity ◽  
Trade Wind ◽  
Stratiform Clouds ◽  
Unique Nature ◽  
Variable Space ◽  
Model Components

Abstract This paper presents the extension of the eddy diffusivity mass flux (EDMF) framework for turbulent transport into the statistical modeling of boundary layer clouds. The advection–diffusion decomposition that defines EDMF is projected onto the turbulent distribution as used in the statistical cloud model. Each EDMF component is thus assigned its own independent probability density function (PDF), resulting in an updraft PDF and a diffusive PDF. This double PDF system is configured and integrated in conserved variable space, with the position and orientation of each PDF determined by its unique nature. The parameterization of the associated updraft/diffusion decomposition of variance introduces close ties to the transport scheme; whereas the grid box mean variance is reconstructed using a prognostic variance budget, the variance of the updraft component is parameterized as a function of the spread among various resolved model updrafts. Individual model components and the scheme as a whole are evaluated in detail against large-eddy simulations of a number of prototype subtropical trade wind cases. The results show that various structures in cloud fraction, condensate, and variance are reproduced. The diffusive PDF acts to represent stratiform clouds; the advective PDF represents cumuliform clouds in conditionally unstable layers. This allows representation of complex scenarios in which both cloud forms occur, such as the transitional trade wind regime featuring cumulus rising into stratocumulus.

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