Spectral Representation of Three-Dimensional Global Data by Expansion in Normal Mode Functions

Kasahara, Akira; Puri, Kamal

doi:10.1175/1520-0493(1981)109<0037:srotdg>2.0.co;2

Cited by 131 publications

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“…tor functions is based on the theoretical work by Kasahara and Puri (1981). They derived a set of three-dimensional orthogonal normal-mode functions (NMFs) and applied it to hemispheric data from the National Center for Environmental Prediction (NCEP).…”

Section: N žAgar Et Al: Normal-mode Function Representation: Softwamentioning

confidence: 99%

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

Žagar

Kasahara²,

Terasaki³

et al. 2015

Geosci. Model Dev.

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Abstract. This article presents new software for the analysis of global dynamical fields in (re)analyses, weather forecasts and climate models. A new diagnostic tool, developed within the MODES project, allows one to diagnose properties of balanced and inertio-gravity (IG) circulations across many scales. In particular, the IG spectrum, which has only recently become observable, can be studied simultaneously in the mass and wind fields while considering the whole model depth in contrast to the majority of studies.The paper includes the theory of normal-mode function (NMF) expansion, technical details of the Fortran 90 code, examples of namelists which control the software execution and outputs of the software application on the ERA Interim reanalysis data set. The applied libraries and default compiler are from the open-source domain. A limited understanding of Fortran suffices for the successful implementation of the software.The presented application of the software to the ERA Interim data set reveals several aspects of the large-scale circulation after it has been partitioned into the linearly balanced and IG components. The global energy distribution is dominated by the balanced energy while the IG modes contribute around 10 % of the total wave energy. However, on sub-synoptic scales, IG energy dominates and it is associated with the main features of tropical variability on all scales. The presented energy distribution and features of the zonally averaged and equatorial circulation provide a reference for the validation of climate models.

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Section: N žAgar Et Al: Normal-mode Function Representation: Softwamentioning

confidence: 99%

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

Žagar

Kasahara²,

Terasaki³

et al. 2015

Geosci. Model Dev.

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“…In this analysis scheme Hough harmonics are used for the horizontal expansion and vertical structure functions for the vertical expansion. In calculation of the vertical structure functions, we used Galerkin's method (Kasahara and Puri 1981) with a fixed value of static stability parameter (g = 30K) for mean surface temperature (T s = 300K) to compare different reanalysis datasets using a common expansion basis function. Due to the application of Hough functions, we can separate atmospheric variables into 3 parts: Rossby (rotational) mode, westward gravity mode and eastward gravity mode (Kasahara 1976;1977).…”

Section: Methodsmentioning

confidence: 99%

Characteristics of the JRA-55 and ERA-Interim Datasets by Using the Three-Dimensional Normal Mode Energetics

Yamagami

Tanaka

2016

SOLA

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In this study, we conducted an energetics analysis of the atmospheric general circulation for up-to-date reanalyses, JRA-55 and ERA-Interim, and compared the result with that of the old reanalysis, JRA-25. Since three-dimensional normal mode functions are used, we can separate the energy spectrum into Rossby and gravity components.According to the comparison between JRA-55 and ERAInterim, it is found that the characteristics of the energy spectrum and the energy interaction are quite similar in zonal wavenumber and vertical mode domains. However, kinetic energy of Rossby modes for JRA-55 is larger than that for ERA-Interim in all wavenumbers. On the other hand, kinetic energy of gravity modes for JRA-55 is smaller than that for ERA-Interim in small wavenumbers. Therefore, one of the features of JRA-55 is that the wind and geopotential fields are close to the geostrophic balance.According to the comparison among JRA-55, ERA-Interim and JRA-25, the imbalance for JRA-55 at zonal wavenumbers 10 to 25 is similar to ERA-Interim and is smaller than that for JRA-25. It is also found that the interactions of available potential energy in the zonal wavenumber domain for JRA-55 is comparable to that for ERA-Interim and is larger than that for JRA-25.(Citation: Yamagami, A., and H. L. Tanaka, 2016: Characteristics of the JRA-55 and ERA-Interim datasets by using the threedimensional normal mode energetics. SOLA, 12, 27−31,

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“…The general solution is given by both, can be of a wave transient type, and does not amplify. (Matsuno, 1966;Kasahara & Puri, 1981;Kasahara, 1984;Santos & Buchmann, 2011).…”

Section: "Chaotic Atmosphere" or Incomplete Models?mentioning

confidence: 99%

Would be the Atmosphere Chaotic?

Santos

Buchmann

2013

Anuário IGEO-UFRJ

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The atmosphere has often been considered "chaotic" when in fact the "chaos" is a manifestation of the models that simulate it, which do not include all the physical mechanisms that exist within it. A weather prediction cannot be perfectly verified after a few days of integration due to the inherent nonlinearity of the equations of the hydrodynamic models. The innovative ideas of Lorenz led to the use of the ensemble forecast, with clear improvements in the quality of the numerical weather prediction. The present study addresses the statement that "even with perfect models and perfect observations, the 'chaotic' nature of the atmosphere would impose a finite limit of about two weeks to the predictability of the weather" as the atmosphere is not necessarily "chaotic", but the models used in the simulation of atmospheric processes are. We conclude, therefore, that potential exists for developments to increase the horizon of numerical weather prediction, starting with better models and observations. Keywords: atmospheric modeling; chaos; numerical weather prediction ResumoA atmosfera tem sido muitas vezes considerada "caótica" quando de fato o "caos" é uma manifestação dos modelos que a simulam, os quais não incluem todos os mecanismos físicos nela existentes. Uma previsão do tempo não se verifica perfeitamente depois de alguns dias de integração devido a não linearidade inerente às equações dos modelos da hidrodinâmica. As ideias inovadoras de Lorenz conduziram ao uso da previsão por conjunto, com melhorias flagrantes na qualidade das previsões. O presente estudo se contrapõe à afirmação de que "mesmo com modelos e observações perfeitas, a natureza 'caótica' da atmosfera imporia um limite finito de cerca de duas semanas para a previsibilidade do tempo", uma vez que a atmosfera não é necessariamente "caótica", mas sim os modelos usados na simulação de seus processos. Conclui-se, portanto, que há espaço para o desenvolvimento no sentido de aumentar os horizontes da previsão numérica do tempo, a partir de melhores modelos e melhores observações. Palavras-chave: modelagem atmosférica; caos; previsão numérica do tempo A n u á r i o d o I n s t i t u t o d e G e o c i ê n c i a s -U F R J

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Spectral Representation of Three-Dimensional Global Data by Expansion in Normal Mode Functions

Cited by 131 publications

References 0 publications

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

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

Characteristics of the JRA-55 and ERA-Interim Datasets by Using the Three-Dimensional Normal Mode Energetics

Would be the Atmosphere Chaotic?

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