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

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.

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

Monthly Weather Review ◽

10.1175/mwr-d-18-0394.1 ◽

2019 ◽

Vol 147 (9) ◽

pp. 3241-3260 ◽

Cited By ~ 1

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.

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

Quarterly Journal of the Royal Meteorological Society ◽

10.1256/qj.03.223 ◽

2004 ◽

Vol 130 (604) ◽

pp. 3365-3383 ◽

Cited By ~ 114

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

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

Monthly Weather Review ◽

10.1175/mwr-d-15-0208.1 ◽

2016 ◽

Vol 144 (3) ◽

pp. 1161-1177 ◽

Cited By ~ 36

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.

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

Monthly Weather Review ◽

10.1175/mwr-d-20-0183.1 ◽

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.

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

Journal of the Atmospheric Sciences ◽

10.1175/2008jas2636.1 ◽

2009 ◽

Vol 66 (6) ◽

pp. 1489-1506 ◽

Cited By ~ 61

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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On the Parameterization of Convective Downdrafts for Marine Stratocumulus Clouds

Monthly Weather Review ◽

10.1175/mwr-d-19-0292.1 ◽

2020 ◽

Vol 148 (5) ◽

pp. 1931-1950 ◽

Cited By ~ 2

Author(s):

Elynn Wu ◽

Handa Yang ◽

Jan Kleissl ◽

Kay Suselj ◽

Marcin J. Kurowski ◽

...

Keyword(s):

Mass Flux ◽

Turbulent Transport ◽

Eddy Diffusivity ◽

Moisture Profile ◽

Marine Stratocumulus ◽

Eddy Simulation ◽

Single Column ◽

Stratocumulus Clouds ◽

Heat And Moisture Transport ◽

Heat And Moisture

Abstract The role of nonlocal transport on the development and maintenance of marine stratocumulus (Sc) clouds in coarse-resolution models is investigated, with a special emphasis on the downdraft contribution. A new parameterization of cloud-top-triggered downdrafts is proposed and validated against large-eddy simulation (LES) for two Sc cases. The applied nonlocal mass-flux scheme is part of the stochastic multiplume eddy-diffusivity/mass-flux (EDMF) framework decomposing the turbulent transport into local and nonlocal contributions. The complementary local turbulent transport is represented with the Mellor–Yamada–Nakanishi–Niino (MYNN) scheme. This EDMF version has been implemented in the Weather Research and Forecasting (WRF) single-column model (SCM) and tested for three model versions: without mass flux, with updrafts only, and with both updrafts and downdrafts. In the LES, the downdraft and updraft contributions to the total heat and moisture transport are comparable and significant. The WRF SCM results show a good agreement between the parameterized downdraft turbulent transport and LES. While including updrafts greatly improves the modeling of Sc clouds over the simulation without mass flux, the addition of downdrafts is less significant, although it helps improve the moisture profile in the planetary boundary layer.

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Eddy Diffusivity/Mass Flux and Shallow Cumulus Boundary Layer: An Updraft PDF Multiple Mass Flux Scheme

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-11-090.1 ◽

2012 ◽

Vol 69 (5) ◽

pp. 1513-1533 ◽

Cited By ~ 36

Author(s):

Kay Sušelj ◽

João Teixeira ◽

Georgios Matheou

Keyword(s):

Boundary Layer ◽

Mass Flux ◽

Eddy Diffusivity ◽

Cloud Base ◽

Model Parameters ◽

Moist Convection ◽

Boundary Layer Turbulence ◽

Eddy Simulation ◽

Shallow Cumulus ◽

Base Closure

Abstract In this study, the eddy diffusivity/mass flux (EDMF) approach is used to combine parameterizations of nonprecipitating moist convection and boundary layer turbulence. The novel aspect of this EDMF version is the use of a probability density function (PDF) to describe the moist updraft characteristics. A single bulk dry updraft is initialized at the surface and integrated vertically. At each model level, the possibility of condensation within the updraft is considered based on the PDF of updraft moist conserved variables. If the updraft partially condenses, it is split into moist and dry updrafts, which are henceforth integrated separately. The procedure is repeated at each of the model levels above. The single bulk updraft ends up branching into numerous moist and dry updrafts. With this new approach, the need to define a cloud-base closure is circumvented. This new version of EDMF is implemented in a single-column model (SCM) and evaluated using large-eddy simulation (LES) results for the Barbados Oceanographic and Meteorological Experiment (BOMEX) representing steady-state convection over ocean and the Atmospheric Radiation Measurement (ARM) case representing time-varying convection over land. The new EDMF scheme is able to represent the properties of shallow cumulus and turbulent fluxes in cumulus-topped boundary layers realistically. The parameterized updraft properties partly account for the behavior of the tail of the PDF of moist conserved variables. It is shown that the scheme is not particularly sensitive to the vertical resolution of the SCM or the main model parameters.

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