A New Gravity Wave Parameterization Including Three-Dimensional Propagation

Amemiya, Arata; Sato, K.

doi:10.2151/jmsj.2016-013

Cited by 34 publications

(37 citation statements)

References 44 publications

(50 reference statements)

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“…This is because the direction and speed of propagation of the waves can depend not only on the background flow but also on the scale of the waves. For example, shorter horizontal wavelength waves propagate faster in the vertical (Kruse and Smith, ) and are more readily refracted (Amemiya and Sato, ). This means that, although not investigated here, the scales of the resolved waves could have an impact on large‐scale atmospheric circulation.…”

Section: Discussionmentioning

confidence: 99%

What can we learn about orographic drag parametrisation from high‐resolution models? A case study over the Rocky Mountains

Niekerk

Elvidge

Sandu

et al. 2020

Quart J Royal Meteoro Soc

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Comprehensive high‐resolution numerical weather prediction models provide a virtual laboratory for modelling the atmospheric flow over complex mountain ranges. In this study, global and regional simulations with horizontal grid spacing ranging from 2 to 32 km, focused over the northern Rocky Mountains, are used to assess the orographic blocking and gravity wave drag parametrisations employed in the Met Office Unified Model (UM) and the European Centre for Medium‐Range Weather Forecasts Integrated Forecasting System (IFS). The total, resolved and parametrised drag components in coarse‐resolution simulations are compared with those in high‐resolution simulations, in which the orographic drag processes are better resolved. The total surface stresses and gravity wave momentum fluxes in the free atmosphere of the global 16 km UM and IFS simulations are shown to compare well with 2 km regional simulations in terms of variability and mean. While the total gravity wave momentum flux is somewhat underestimated by both global models, its vertical distribution is well captured. The “seamlessness” of the parametrisation scheme is then assessed by comparing the total orographic stress – and its components – across several horizontal resolutions of the UM. The surface stress remains relatively constant across resolutions, such that the reduction in resolved orographic stress at coarser resolutions is compensated for by an almost equivalent increase in parametrised orographic stress. However, the parametrised orographic gravity wave momentum flux in the free atmosphere remains almost constant with resolution, failing to compensate for the lack of resolved flux at coarse resolutions. This leads to an underestimation of the total gravity wave drag at coarser resolutions. Further analysis suggests that this underestimation is due to the monochromatic wave assumption made by the gravity wave drag parametrisation scheme.

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Section: Discussionmentioning

confidence: 99%

What can we learn about orographic drag parametrisation from high‐resolution models? A case study over the Rocky Mountains

Niekerk

Elvidge

Sandu

et al. 2020

Quart J Royal Meteoro Soc

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“…The quantitative knowledge about the parameters of NIGWs with vertical and seasonal dependence obtained in this study is useful for reducing uncertainties in the GW parameterizations implemented in most climate models. In future studies, the horizontal propagation of GWs (e.g., Song & Chun, 2008), the horizontal refraction in the background wind shear (e.g., Amemiya & Sato, 2016;Preusse et al, 2009;Sato et al, 2009), the horizontal advection by the background wind (e.g., Sato et al, 2012;Smith, 1980) and/or their intrinsic group velocities, and the intermittency of GW momentum fluxes (e.g., de la Cámara et al, 2014;Hertzog et al, 2012;Jewtoukoff et al, 2015;Plougonven et al, 2017) should be examined based on PANSY radar observations. Combining these data with numerical simulations will be useful.…”

Section: Summary and Concluding Remarksmentioning

confidence: 99%

Statistical Characteristics of Gravity Waves With Near‐Inertial Frequencies in the Antarctic Troposphere and Lower Stratosphere Observed by the PANSY Radar

et al. 2018

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Gravity waves (GWs) have temporally and spatially small scales. Observations of GWs have been limited especially in the polar region due to its harsh environment. The purpose of this study is to elucidate the statistical characteristics of GWs in the Antarctic troposphere and lower stratosphere based on the continuous data over a year from 1 October 2015 to 30 September 2016 using the full system of the Program of the Antarctic Syowa MST/IS Radar (PANSY) radar at Syowa Station (69.0°S, 39.6°E). Such continuous observations over a long duration are unprecedented for high‐power Mesosphere‐Stratosphere‐Troposphere (MST) radars at any latitude. The frequency power spectra of horizontal wind fluctuations reveal a clear isolated maximum around the inertial frequency (f) in the lower stratosphere. A statistical analysis is performed, focusing on the GWs with near‐inertial frequencies (NIGWs) that are dominant in the lower stratosphere. According to the results of hodograph analyses, there are a considerable proportion of NIGWs propagating energy downward in the upper troposphere during all seasons, as well as in the winter stratosphere above a height of 15 km, whereas NIGWs with upward group velocities are dominant in the lower troposphere and the lowermost stratosphere. These results suggest that there are NIGW sources on the ground and around the tropopause during all seasons and in the stratosphere and/or above in winter. Plausible candidates for these sources are topography, the tropospheric jet, and the polar night jet. The statistical characteristics of NIGWs, such as horizontal phase velocity, provide powerful support for our inferences of wave sources.

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“…Implementation in a general circulation model was found to provide significant improvements to the circulation and its variability (Choi and Chun, ). An orographic gravity wave parameterization incorporating three‐dimensional propagation and including the effect of the horizontal refraction of the waves has also been developed by Amemiya and Sato () and implemented in a climate model. Although significant differences are found in the distribution of the fluxes, the differences in the mean winds and variability were minor.…”

Section: Phenomena Remaining Outside the Framework Of Parameterizationsmentioning

confidence: 99%

How does knowledge of atmospheric gravity waves guide their parameterizations?

Plougonven

Cámara

Hertzog

et al. 2020

Quart J Royal Meteoro Soc

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This note discusses the relation between our knowledge of gravity waves and the parameterization of their effects in global models. Improving these parameterizations represents a major motivation for current research on atmospheric gravity waves. Indeed, as a major portion of the gravity wave spectrum is on the subgrid scale, parameterizations are used to represent their impacts on large-scale flow. Gravity wave parameterizations generally share a common framework, with assumptions on their propagation (columnar only) and their sources (tropospheric only). These assumptions are highly justified to leading order, and parameterizations have been successful in allowing models to reproduce a number of middle-atmospheric features. Once this framework is set up, specifying the sources constitutes a poorly constrained step. In practice, sources are tuned to a large extent in order to improve the modelled atmospheric circulation, a process that includes compensating for model biases. Consequently, significant efforts have been made to better quantify the sources of gravity waves, combining observations, modelling and theory, stimulating ground-breaking progress in our knowledge and understanding of atmospheric gravity waves.As emphasized in this note, however, the transfer to parameterizations is not straightforward: knowledge of the characteristics of lower-stratospheric gravity waves does not directly translate into input parameters for parameterizations.The example of intermittency is used to illustrate the impact of a (minor) shift in the parameterization framework, leading to a redistribution of the resulting forcing in the middle atmosphere. Recent studies have highlighted a number of phenomena which fall outside of the classical framework of parameterizations, notably lateral propagation and secondary generation. This growing body of evidence calls for further investigations to determine which of these phenomena could have systematic and robust implications for the larger-scale flow. To retain appropriate simplicity of the parameterizations, efforts to identify acceptable simplifications should also be undertaken in parallel, in a framework of a model hierarchy. K E Y W O R D Sclimate modelling, gravity waves, middle atmosphere, parameterizations Q J R Meteorol Soc. 2020;146:1529-1543.wileyonlinelibrary.com/journal/qj

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A New Gravity Wave Parameterization Including Three-Dimensional Propagation

Cited by 34 publications

References 44 publications

What can we learn about orographic drag parametrisation from high‐resolution models? A case study over the Rocky Mountains

What can we learn about orographic drag parametrisation from high‐resolution models? A case study over the Rocky Mountains

Statistical Characteristics of Gravity Waves With Near‐Inertial Frequencies in the Antarctic Troposphere and Lower Stratosphere Observed by the PANSY Radar

How does knowledge of atmospheric gravity waves guide their parameterizations?

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