A framework to evaluate IMEX schemes for atmospheric models

Guba, Oksana; Taylor, Mark A.; Bradley, Andrew M.; Bosler, Peter Andrew; Steyer, Andrew

doi:10.5194/gmd-2020-178

Cited by 2 publications

(2 citation statements)

References 12 publications

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“…(2019) and Guba et al. (2020), with a second‐order accurate coupling of a high‐stage high‐CFL scheme for the explicit terms and a Diagonally Implicit Runge Kutta (DIRK) scheme for the implicit terms. Due to the use of the Laprise mass coordinate, the vertical acoustic waves are isolated to only two terms in the equations for vertical velocity and geopotential solved at level interfaces, leading to an implicit system for a single variable.…”

Section: Model Descriptionmentioning

confidence: 99%

Convection‐Permitting Simulations With the E3SM Global Atmosphere Model

Caldwell

Terai

Hillman

et al. 2021

J Adv Model Earth Syst

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This paper describes the first implementation of the Δx = 3.25 km version of the Energy Exascale Earth System Model (E3SM) global atmosphere model and its behavior in a 40‐day prescribed‐sea‐surface‐temperature simulation (January 20 through February 28, 2020). This simulation was performed as part of the DYnamics of the Atmospheric general circulation Modeled On Non‐hydrostatic Domains (DYAMOND) Phase 2 model intercomparison. Effective resolution is found to be the horizontal dynamics grid resolution despite using a coarser grid for physical parameterizations. Despite this new model being in an immature and untuned state, moving to 3.25 km grid spacing solves several long‐standing problems with the E3SM model. In particular, Amazon precipitation is much more realistic, the frequency of light and heavy precipitation is improved, agreement between the simulated and observed diurnal cycle of tropical precipitation is excellent, and the vertical structure of tropical convection and coastal stratocumulus look good. In addition, the new model is able to capture the frequency and structure of important weather events (e.g., tropical cyclones, extratropical cyclones including atmospheric rivers, and cold air outbreaks). Interestingly, this model does not get rid of the erroneous southern branch of the intertropical convergence zone nor the tendency for strongest convection to occur over the Maritime Continent rather than the West Pacific, both of which are classic climate model biases. Several other problems with the simulation are identified, underscoring the fact that this model is a work in progress.

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Section: Model Descriptionmentioning

confidence: 99%

Convection‐Permitting Simulations With the E3SM Global Atmosphere Model

Caldwell

Terai

Hillman

et al. 2021

J Adv Model Earth Syst

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“…NH simulations use a Horizontally Explicit Vertically Implicit approach (HEVI; Satoh, 2002), discretized with an IMplicit‐EXplicit (IMEX) Runge Kutta method (Ascher et al., 1997), which combines an explicit KGU53 method for all horizontal derivatives and an implicit method for terms responsible for vertically propagating acoustic waves, similar to the IMEX methods constructed in Guba et al. (2020).…”

Section: Model Description and Methodologymentioning

confidence: 99%

An Assessment of Nonhydrostatic and Hydrostatic Dynamical Cores at Seasonal Time Scales in the Energy Exascale Earth System Model (E3SM)

Liu

Ullrich

Guba

et al. 2022

J Adv Model Earth Syst

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The hydrostatic (H) approximation is widely used in numerical atmospheric models to simplify the underlying fluid equations and avoid the timestep restrictions imposed by vertically propagating waves (Saito et al., 2007;Salmon, 1988). Under this approximation the atmosphere is assumed to be continuously in hydrostatic equilibrium, with a balance between gravity and vertical pressure gradient; in essence, any hydrostatic imbalances are assumed to be corrected instantaneously. The hydrostatic approximation can be shown to be a reasonable assumption when the horizontal scale is much larger than the vertical scale. However, nonhydrostatic (NH) effects are crucial to the simulation of certain fine-scale phenomena, such as deep convection and flow over topography; in these circumstances, departures from hydrostatic equilibrium need to be taken into account. While the horizontal grid spacing necessary for producing NH effects is generally around 10 km, recent studies have also been shown that the inclusion of moist physics can lead to significant divergence between H and NH models even around 36 km grid spacing (Gao et al., 2017;Yang et al., 2017). While this grid spacing is finer than the typical grid spacing for global climate models, recent pushes toward higher horizontal resolution in atmospheric models have placed us squarely in this regime (Caldwell et al., 2021;Haarsma et al., 2016;Stevens et al., 2019). Consequently, it is both important and timely to investigate NH effects in global climate modeling systems, particularly in the context of seasonal to climatological scale simulations.

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A framework to evaluate IMEX schemes for atmospheric models

Cited by 2 publications

References 12 publications

Convection‐Permitting Simulations With the E3SM Global Atmosphere Model

Convection‐Permitting Simulations With the E3SM Global Atmosphere Model

An Assessment of Nonhydrostatic and Hydrostatic Dynamical Cores at Seasonal Time Scales in the Energy Exascale Earth System Model (E3SM)

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