Is Shallow Convection Sensitive to Environmental Heterogeneities?

Kurowski, Marcin J.; Sušelj, K.; Grabowski, Wojciech W.

doi:10.1029/2018gl080847

Cited by 14 publications

(24 citation statements)

References 40 publications

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“…Therefore, the underlying assumption is that the updrafts are formed by the most buoyant/energetic portions of the near-surface air [19]. In the model, the plumes are assumed horizontally homogeneous and interact with the properties of grid-mean fields via entrainment and buoyancy [20].…”

Section: Mass-flux Parameterizationmentioning

confidence: 99%

Towards Unifying the Planetary Boundary Layer and Shallow Convection in CAM5 with the Eddy-Diffusivity/Mass-Flux Approach

et al. 2019

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The modular structure of the boundary layer and convection parameterizations in atmospheric models have long been affecting the numerical representation of subgrid-scale motions and their mutual interactions. A promising alternative, the eddy-diffusivity/mass-flux approach (EDMF), has the potential for unifying the existing formulations into a consistent scheme and improving some of the long-standing issues. This study documents a step towards developing such a unified approach by implementing a stochastic multi-plume EDMF scheme into the Community Atmosphere Model (Version 5.0). Its performance in single-column mode is evaluated against the control parameterization and large-eddy simulation (LES) for two benchmark cases: marine and continental shallow convection. Overall, the results for the two parameterizations agree well with each other and with LES in terms of mean profiles of moist conserved variables and their vertical fluxes, as well as the updraft properties. However, systematic differences between the two schemes, especially for transient continental convection, are also documented. Using EDMF helps improve some of the parameterized features of shallow convection. In particular, for the highest tested vertical resolution, the EDMF cloud base and top heights and the vertical fluxes of energy and water are remarkably close to LES.

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Section: Mass-flux Parameterizationmentioning

confidence: 99%

Towards Unifying the Planetary Boundary Layer and Shallow Convection in CAM5 with the Eddy-Diffusivity/Mass-Flux Approach

et al. 2019

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“…Physical processes governing the evolution of the stratocumulus-topped boundary layer (STBL)-such as cloud-top radiative cooling, entrainment, evaporative cooling, surface fluxes, wind shear, and precipitation-widely range on spatial and temporal scales, and modeling Sc clouds is quite challenging as a result (e.g., Lilly 1968;Stevens 2002;Wood 2012). Efforts through both observational campaigns (e.g., Stevens et al 2003;Malinowski et al 2013;Crosbie et al 2016) and high-resolution numerical modeling (e.g., Stevens et al 2005;Kurowski et al 2009;Yamaguchi and Randall 2012;Chung et al 2012;Blossey et al 2013;de Lozar and Mellado 2015;Pedersen et al 2016;Mellado et al 2018;Matheou and Teixeira 2019) have significantly advanced our understanding of the physics of Sc clouds. These physical insights are important for numerical weather prediction (NWP) and general circulation models (GCMs) where grid resolution is coarse.…”

Section: Introductionmentioning

confidence: 99%

“…The combined effect of both evaporative and radiative cooling-the former typically enhanced by wind shear (Mellado et al 2014)-destabilizes the top of cloud layer through buoyancy reversal that leads to the formation of negatively buoyant weak downdrafts. This process is often considered responsible for the generation of cloud holes in largely unbroken Sc clouds (Gerber et al 2005;Kurowski et al 2009). Many small-scale phenomena (e.g., entrainment, shear, evaporative cooling, cloud microphysics) are at play in the origin of downdrafts and can strongly influence vertical mixing .…”

Section: Introductionmentioning

confidence: 99%

On the Parameterization of Convective Downdrafts for Marine Stratocumulus Clouds

Yang

Kleissl

et al. 2020

Monthly Weather Review

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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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“…Piggybacking was also applied in simulations where one of the thermodynamic sets applied homogenization of the cloud environment to explore whether environmental heterogeneities, such as remnants of previous clouds, affect subsequent cloud developments; Kurowski et al (2019). The difference between driver and piggybacker was in either including or excluding the homogenization of the cloud environment.…”

Section: Applications Of the Piggybacking Methodologymentioning

confidence: 99%

“…Data availability. The used data in this publication were taken from https://doi.org/10.1175/JAS-D-14-0231.1 (Grabowski, 2014), https://doi.org/10.1175/JAS-D-14-0307.1 (Grabowski, 2015), and https://doi.org/10.1175/JAS-D-18-0105.1 (Grabowski, 2018), https://doi.org/10.1175/JAS-D-15-0091.1 (Grabowski and Jarecka, 2015), https://doi.org/10.1175/JAS-D-15-0367.1 (Grabowski and Morrison, 2016), and https://doi.org/10.1175/JAS-D-16-0255.1 (Grabowski and Morrison, 2017), https://doi.org/10.1175/JCLI-D-19-0007.1 (Grabowski and Prein, 2019), and https://doi.org/10.1029/2018GL080847 (Kurowski et al, 2019).…”

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confidence: 99%

Separating physical impacts from natural variability using piggybacking technique

Grabowski¹

2019

Adv. Geosci.

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Abstract. In a chaotic system, like moist convection, it is difficult to separate the impact of a physical process from effects of natural variability. This is because modifying even a small element of the system physics typically leads to a different system evolution and it is difficult to tell whether the difference comes from the physical impact or it merely represents a different flow realization. This paper discusses a relatively simple and computationally efficient modelling methodology that allows separation of the two. The methodology is referred to as the piggybacking or the master-slave approach. The idea is to use two sets of thermodynamic variables (the temperature, water vapor, and all aerosol, cloud, and precipitation variables) in a single cloud simulation. The two sets differ in a specific element of the physics, such as aerosol properties, microphysics parameterization, large-scale forcing, environmental profiles, etc. One thermodynamic set is coupled to the dynamics and drives the simulated flow, and the other set piggybacks the flow, that is, thermodynamic variables are carried by the flow but they do not affect it. By switching the two sets (i.e. the set driving the simulation becomes the piggybacking one, and vice versa), the impact on the cloud dynamics can be evaluated. This paper provides details of the method and reviews results of its application to such problems as the postulated deep convection invigoration in polluted environments, the impact of changes in environmental profiles (e.g., due to climate change) on convective dynamics, and the role of cloud-layer heterogeneities for shallow convective cloud field evolution. Prospects for applying piggybacking technique to other areas of atmospheric simulation (e.g., weather prediction or geoengineering) are also mentioned.

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Is Shallow Convection Sensitive to Environmental Heterogeneities?

Cited by 14 publications

References 40 publications

Towards Unifying the Planetary Boundary Layer and Shallow Convection in CAM5 with the Eddy-Diffusivity/Mass-Flux Approach

Towards Unifying the Planetary Boundary Layer and Shallow Convection in CAM5 with the Eddy-Diffusivity/Mass-Flux Approach

On the Parameterization of Convective Downdrafts for Marine Stratocumulus Clouds

Separating physical impacts from natural variability using piggybacking technique

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