A High‐Resolution Whole‐Atmosphere Model With Resolved Gravity Waves and Specified Large‐Scale Dynamics in the Troposphere and Stratosphere

Becker, Erich; Vadas, Sharon L.; Bossert, Katrina; Harvey, V. L.; Zülicke, Christoph; Hoffmann, Lars

doi:10.1029/2021jd035018

Cited by 47 publications

(82 citation statements)

References 79 publications

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“…One explanation for the model easterly wind bias in the polar winter MLT is that the model omits higher order GWs, and thus the eastward drag caused by these GWs. Other known deficiencies in the existing GW parameterization that may contribute to the easterly wind bias in the model include: the absence of oblique GW propagation (e.g., Sato et al, 2009;Thurairajah et al, 2017Thurairajah et al, , 2020, the need to modify the GW source spectrum (e.g., Liu & Roble, 2002;Pramitha et al, 2020), the need to impose GW sources at all altitudes (e.g., Ribstein et al, 2022) including tropospheric jet exit regions and the stratospheric polar vortex (e.g., Becker et al, 2022;Dörnbrack et al, 2018;Sato & Yoshiki, 2008), and the need to tune GW parameterizations according to simulated tidal variability (e.g., Becker, 2017). Future work will investigate running the model at 0.25° horizontal resolution, following Liu et al (2014), to quantify the sensitivity of the easterly wind bias to model resolution.…”

Section: Discussionmentioning

confidence: 99%

Evaluation of Polar Winter Mesopause Wind in WACCMX+DART

et al. 2022

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This work evaluates zonal winds in both hemispheres near the polar winter mesopause in the Whole Atmosphere Community Climate Model (WACCM) with thermosphere‐ionosphere eXtension combined with data assimilation using the Data Assimilation Research Testbed (DART) (WACCMX+DART). We compare 14 years (2006–2019) of WACCMX+DART zonal mean zonal winds near 90 km to zonal mean zonal winds derived from Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) geopotential height measurements during Arctic mid‐winter. 10 years (2008–2017) of WACCMX+DART zonal mean zonal winds are compared to SABER in the Antarctic mid‐winter. It is well known that WACCM, and WACCM‐X, zonal winds at the polar winter mesopause exhibit a strong easterly (westward) bias. One explanation for this is that the models omit higher order gravity waves (GWs), and thus the eastward drag caused by these GWs. We show for the first time that the model winds near the polar winter mesopause are in closer agreement with SABER observations when the winds near the stratopause are weak or reversed. The model and observed mesosphere and lower thermosphere winds agree most during dynamically disturbed times often associated with minor or major sudden stratospheric warming events. Results show that the deceleration of the stratospheric and mesospheric polar night jet allows enough eastward GWs to propagate into the mesosphere, driving eastward zonal winds that are in agreement with the observations. Thus, in both hemispheres, the winter polar night jet speed and direction near the stratopause may be a useful proxy for model fidelity in the polar winter upper mesosphere.

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Section: Discussionmentioning

confidence: 99%

Evaluation of Polar Winter Mesopause Wind in WACCMX+DART

et al. 2022

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“…Determine how the polar vortex contributes as a source of primary GWs during strong vortex states. For example, Liu (2017) and Becker et al (2022a) observed/simulated in-situ generation of GWs by a disturbed polar vortex. 9.…”

Section: Figurementioning

confidence: 99%

Improving ionospheric predictability requires accurate simulation of the mesospheric polar vortex

Harvey

Randall

Bailey

et al. 2022

Front. Astron. Space Sci.

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The mesospheric polar vortex (MPV) plays a critical role in coupling the atmosphere-ionosphere system, so its accurate simulation is imperative for robust predictions of the thermosphere and ionosphere. While the stratospheric polar vortex is widely understood and characterized, the mesospheric polar vortex is much less well-known and observed, a short-coming that must be addressed to improve predictability of the ionosphere. The winter MPV facilitates top-down coupling via the communication of high energy particle precipitation effects from the thermosphere down to the stratosphere, though the details of this mechanism are poorly understood. Coupling from the bottom-up involves gravity waves (GWs), planetary waves (PWs), and tidal interactions that are distinctly different and important during weak vs. strong vortex states, and yet remain poorly understood as well. Moreover, generation and modulation of GWs by the large wind shears at the vortex edge contribute to the generation of traveling atmospheric disturbances and traveling ionospheric disturbances. Unfortunately, representation of the MPV is generally not accurate in state-of-the-art general circulation models, even when compared to the limited observational data available. Models substantially underestimate eastward momentum at the top of the MPV, which limits the ability to predict upward effects in the thermosphere. The zonal wind bias responsible for this missing momentum in models has been attributed to deficiencies in the treatment of GWs and to an inaccurate representation of the high-latitude dynamics. In the coming decade, simulations of the MPV must be improved.

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“…The HIAMCM (HIgh Altitude Mechanistic general Circulation Model) (Becker and Vadas, 2020;Becker et al, 2022) is a new, high-altitude version of the KMCM (Kühlungsborn Mechanistic general Circulation Model). The HIAMCM employs a spectral dynamical core with a terrain-following hybrid vertical coordinate.…”

Section: Hiamcmmentioning

confidence: 99%

“…Nevertheless, the key features of a climate model (topography, simple ocean model, radiative transfer, boundary layer processes, tropospheric moisture cycle) are fully taken into account. Also note that the HIAMCM is currently the only GWresolving whole atmosphere model that can be nudged to reanalysis in the troposphere and stratosphere, allowing for the simulation of observed events (Becker et al, 2022).…”

Section: Hiamcmmentioning

confidence: 99%

“…Second, we now have more model studies with GW-permitting resolution not using any GW parametrization (e.g. Liu et al, 2014;Siskind, 2014;Becker and Vadas, 2020;Okui et al, 2021;Becker et al, 2022;Okui et al, 2022). These models reach at least similar performance for the MLT and better performance for the thermosphere than GW-parametrizing GCMs as they include middle atmosphere sources and oblique propagation, despite the fact that they resolve only GWs with horizontal wavelengths longer than ≈200km.…”

Section: Appendix E: the Relative Importance Of Different Horizontal ...mentioning

confidence: 99%

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Satellite observations of gravity wave momentum flux in the mesosphere / lower thermosphere (MLT): feasibility and requirements

Chen¹,

Ntokas²,

Linder³

et al. 2022

Preprint

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Abstract. In the recent decade it became evident that we need to revise our picture of how gravity waves (GWs) reach the mesosphere and lower thermosphere (MLT). This has consequences for not just the properties of the GWs itself, but in particular for the global circulation in the MLT. Information on spectral distribution, direction and zonal mean GW momentum flux is required to test the theoretical and modeling findings. In this study, we propose a constellation of two CubeSats for observing mesoscale GWs in the MLT region by means of temperature limb sounding in order to derive such constraints. Each CubeSat deploys a highly miniaturized spatial heterodyne interferometer (SHI) for the measurement of global oxygen atmospheric band emissions. From these emissions, the 3-D temperature structure can be inferred. We propose to obtain four independent observation tracks by splitting the interferograms in the center and thus gaining 2 observation tracks for each satellite. We present a feasibility study of this concept based on self-consistent, high-resolution global model data. This yields a full chain of end-to-end (E2E) simulation incorporating 1) orbit simulation; 2) airglow forward modelling; 3) tomographic temperature retrieval; 4) 3-D wave analysis; and 5) GW momentum flux (GWMF) calculation. The simulation performance is evaluated by comparing the retrieved zonal-mean GWMF with that computed directly from the model wind data. A major question to be considered in our assessment is the minimum number of tracks required for the derivation of 3D GW parameters with sufficient accuracy. In particular, our simulations show that the GW polarization relations are still valid in the MLT region and can thus be employed for inferring GWMF from the 3--D temperature distributions. Based on the E2E simulations for gaining zonal-mean climatologies of GW momentum flux, we demonstrate that our approach is robust and stable, given a four-track observation geometry and the expected instrument noise under nominal operation conditions. Using phase-speed-direction spectra we show also that the properties of individual wave events are recovered when employing four tracks. Finally, we discuss the potential of the proposed observations to address current topics in the GW research. We outline for which investigations ancillary data are required to answer science questions.

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A High‐Resolution Whole‐Atmosphere Model With Resolved Gravity Waves and Specified Large‐Scale Dynamics in the Troposphere and Stratosphere

Abstract: Atmospheric general circulation models (GCMs) are valuable tools to study large-scale atmospheric variability and its sensitivities to external perturbations (

Cited by 47 publications

References 79 publications

Evaluation of Polar Winter Mesopause Wind in WACCMX+DART

Evaluation of Polar Winter Mesopause Wind in WACCMX+DART

Improving ionospheric predictability requires accurate simulation of the mesospheric polar vortex

Satellite observations of gravity wave momentum flux in the mesosphere / lower thermosphere (MLT): feasibility and requirements

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