Normal-mode function representation of global 3-D data sets: open-access software for the atmospheric research community

Žagar, Nedjeljka; Kasahara, Akira; Terasaki, Koji; Tribbia, Joseph; Tanaka, Hiroshi

doi:10.5194/gmd-8-1169-2015

Cited by 51 publications

(60 citation statements)

References 69 publications

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“…We decompose the geopotential height and zonal and meridional wind fields into normal modes according to the framework of Kasahara and Puri (), Žagar and Franzke (), and Žagar et al . (). The ERA‐Interim reanalyses are decomposed into Kelvin, IG, and Rossby waves using the three‐dimensional normal‐mode function decomposition.…”

Section: Methodsmentioning

confidence: 97%

“…The decomposition is based on theoretical work by Kasahara and Puri () and Phillips (); this decomposition was recently updated for modern‐day data by Žagar et al . (). This modal decomposition projects the zonal and meridional wind and geopotential height fields on to a set of predefined basis functions, which are eigensolutions of the linearized equations.…”

Section: Methodsmentioning

confidence: 97%

“…The details of the procedure are described in Žagar et al . (). Inverse filtering provides flow information on terrain‐following levels, which is then interpolated to the selected pressure levels using climate data operators (CDO: Schulzweida et al .…”

Section: Methodsmentioning

confidence: 97%

“…In the NMF software tool described in Žagar et al . (), the NMF modes are ordered in such a way that the Kelvin wave is the lowest order eastward‐propagating IG mode and the mixed Rossby–gravity wave is the lowest order westward‐propagating Rossby mode.…”

Section: Methodsmentioning

confidence: 99%

“…Žagar et al . () updated this approach and provided an open‐source software tool to compute these normal‐mode decompositions from three‐dimensional reanalysis and model data.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Systematic decomposition of the MJO and its Northern Hemispheric extratropical response into Rossby and inertio‐gravity components

Franzke¹,

Jelić

Lee

et al. 2019

Quart J Royal Meteoro Soc

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The Madden–Julian Oscillation (MJO) is the dominant form of intraseasonal variability in the Tropics. The MJO is a complex convectively coupled phenomenon, which is still poorly represented in the current generation of climate models, and our understanding of its essential dynamics and its influence on the midlatitude circulation is still incomplete. Here, we use a normal‐mode decomposition method to decompose the MJO systematically into Kelvin, inertio‐gravity (IG), and Rossby‐wave components in the ERA‐Interim reanalysis data for the period 1980–2015 to provide a climatology of the eight MJO phases for the Kelvin, IG, and Rossby‐wave components. Our analysis shows that the Rossby modes provide a larger contribution to the magnitude of the MJO in terms of geopotential height and winds than the Kelvin wave and IG modes. Moreover, the kinetic energy associated with the Rossby modes of the MJO accounts for about 93% of the kinetic energy. Our decomposition also shows that the Kelvin wave is the dominant mode in the unbalanced wave part, which is flanked by Rossby waves on both sides of the Equator, consistent with previous studies. The extratropical response to the MJO also consists of both IG and Rossby‐wave components in the Northern Hemisphere (NH). The midlatitude MJO response is also linked to well‐known teleconnection patterns like the North Atlantic Oscillation and the Pacific–North American pattern. The transient NH atmospheric response is fast, of the order of 5–7 days. While the extratropical response is dominated by Rossby waves, IG waves also show a prominent response in the NH.

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Section: Methodsmentioning

confidence: 97%

Section: Methodsmentioning

confidence: 97%

Section: Methodsmentioning

confidence: 97%

Section: Methodsmentioning

confidence: 99%

“…Žagar et al . () updated this approach and provided an open‐source software tool to compute these normal‐mode decompositions from three‐dimensional reanalysis and model data.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Systematic decomposition of the MJO and its Northern Hemispheric extratropical response into Rossby and inertio‐gravity components

Franzke¹,

Jelić

Lee

et al. 2019

Quart J Royal Meteoro Soc

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Systematic decomposition of the Madden‐Julian Oscillation into balanced and inertio‐gravity components

Žagar

Franzke²

2015

Geophysical Research Letters

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We present a new method for the three‐dimensional multivariate decomposition of the Madden‐Julian Oscillation (MJO) into balanced and inertio‐gravity (IG) components. The method analyzes global fields with no filtering involved, and it provides a quantitative comparison between the contribution of the Rossby, Kelvin, and other balanced and IG modes to the MJO circulation and its teleconnections. Results based on the ERA Interim reanalysis data and the multivariate MJO index show that the Rossby mode with the lowest meridional index is the largest contributor to the MJO circulation over the Pacific. A smaller role of the Kelvin mode is diagnosed over the Indian Ocean and the maritime continent. The MJO teleconnections in the polar stratosphere appear associated with the leading balanced vertical modes. The presented method shows new ways of evaluating the MJO structure and its global impacts in weather and climate models.

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A high‐accuracy global prognostic model for the simulation of Rossby and gravity wave dynamics

Vasylkevych

Žagar

2021

Quart J Royal Meteoro Soc

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A model for studying Transient Inertia-Gravity And Rossby wave dynamics (TIGAR) is introduced. The presented horizontal component of the model solves the nonlinear rotating shallow-water equations on the sphere using Hough harmonics. Spectral modelling using Hough harmonics as basis functions describes atmospheric dynamics in terms of physically identifiable structures: Rossby and inertia-gravity eigensolutions of linearized primitive equations. This offers an attractive framework for detangling gravity wave dynamics in high-resolution simulations. Accurate computations are achieved through the use of higher order integrating factor and exponential time-differencing methods, leading to a major increase in computational efficiency and stability. A comparison with classical time-stepping schemes shows accuracy improvements of several orders of magnitude at no additional computational cost. In particular, stability gains are achieved through enhanced accuracy and efficiency in the computation of gravity waves, rather than through their damping. In the new framework, reduced models using Rossby and gravity waves aimed at studying dynamical aspects of data assimilation or wave interactions are easily implemented.

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Normal-mode function representation of global 3-D data sets: open-access software for the atmospheric research community

Cited by 51 publications

References 69 publications

Systematic decomposition of the MJO and its Northern Hemispheric extratropical response into Rossby and inertio‐gravity components

Systematic decomposition of the MJO and its Northern Hemispheric extratropical response into Rossby and inertio‐gravity components

Systematic decomposition of the Madden‐Julian Oscillation into balanced and inertio‐gravity components

A high‐accuracy global prognostic model for the simulation of Rossby and gravity wave dynamics

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