Space-Time Spectral Analysis and its Applications to Atmospheric Waves

Hayashi, Yoshikazu

doi:10.2151/jmsj1965.60.1_156

Cited by 217 publications

(150 citation statements)

References 47 publications

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“…1. To construct this plot, we first calculate a wavenumber-frequency spectrum [see Hayashi (1982) for details on this] for the precipitation at all latitudes between 15°N and 15°S using 96-day windows, which overlap by 60 days. Wheeler and Kiladis (1999) use outgoing longwave radiation in their study; however precipitation is the diagnostic most analogous with outgoing longwave radiation in a model without clouds.…”

Section: Control Simulation Kelvin Wavesmentioning

confidence: 99%

Convectively Coupled Kelvin Waves in an Idealized Moist General Circulation Model

Frierson

2007

J. Atmos. Sci.

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The dynamics of convectively coupled Kelvin waves and their dependence on convection scheme parameters are studied within a simplified moist general circulation model. The model consists of the primitive equations on the sphere over zonally symmetric aquaplanet, slab mixed layer ocean boundary conditions, and idealized physical parameterizations including gray radiative transfer and a simplified Betts-Miller convection scheme. This framework allows the authors to study the dependence of Kelvin waves on quantities such as the gross moist stability in a clean manner.A control simulation with the model produces convectively coupled Kelvin waves that are remarkably persistent and dominate the variability within the Tropics. These waves propagate with an equivalent depth of Ϸ40 m. Linear regression analysis with respect to a Kelvin-filtered time series shows that the waves are driven by evaporation-wind feedback and have structures broadly consistent with theoretical predictions for Kelvin waves.Next, the determination of the speed and structure of the Kelvin waves is studied by examining the response of the waves to changes in convection scheme parameters. When the convective relaxation time is lengthened, the waves are damped and eventually are completely eliminated. The propagation speed additionally increases with longer relaxation time. Then changes to a convection scheme parameter that essentially controls the fraction of convective versus large-scale precipitation are examined. When some large-scale precipitation occurs, the waves increase in strength, propagate more slowly, and move to larger scales. However, when mostly large-scale precipitation occurs, the Kelvin wave disappears, and the Tropics are dominated by tropical storm-like variability. The decrease in speed is related here to the gross moist stability of the atmosphere, which is reduced with increased large-scale precipitation.

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Section: Control Simulation Kelvin Wavesmentioning

confidence: 99%

Convectively Coupled Kelvin Waves in an Idealized Moist General Circulation Model

Frierson

2007

J. Atmos. Sci.

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“…It provides an interesting test of the POP analysis method. Since the oscillation is a fairly well-defined, zonally distributed feature, it can also be investigated using standard frequency-wave number analysis methods [Hayashi, 1982]. Thus the results of the POP analysis may be validated by an established alternative, conceptually different statistical technique.…”

Section: Application To the Equatorial 30-to 60-day Wavementioning

confidence: 99%

Principal oscillation pattern analysis of the 30‐ to 60‐day oscillation in general circulation model equatorial troposphere

et al. 1988

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A new technique is described for identifying time-dependent patterns (i.e., "principal oscillation patterns," or POPs) in a set of geophysical time series. POPs are defined as the normal modes of a linear dynamical representation of the data in terms of a first-order autoregressive vector process with residual noise forcing. POPs associated with real eigenvalues represent nonpropagating, nonoscillatory patterns which decay exponentially. POPs associated with complex eigenvalues occur in complex conjugate pairs and can represent standing wave structures (if one pattern is much stronger than the other), propagating waves (if both patterns are periodic and have the same structure except for a quarter-wavelength shift) or, in general, an arbitrary amphidromal oscillation. After the POPs have been defined for a selected set of primary variables, associated correlation or composite patterns may be derived for additional secondary fields to gain further insight into the structure of the interaction mechanisms. Principal Oscillation Pattern AnalysisIn this paper we describe and apply a new technique for analyzing spatial and temporal variability in a multicomponent data set. The "principal oscillation pattern" (POP) analysis identifies coherent migrating, standing, or otherwise changing patterns of the system without prior knowledge of the system dynamics. The basic approach is to represent the vector time series as the output of a multivariate first-order autoregressive process forced by residual noise (not necessarily white noise). The process matrix is estimated from the data. The POPs are defined as the real or complex eigenvectors of the process matrix, with associated real or complex eigenvalues. Complex POPs occur in complex conjugate pairs and represent damped amphidromal oscillations (including propagating and standing waves as special cases), while real POPs occur as singlets and describe nonpropagating, nonoscillating, damped patterns. In the continuous case the POP analysis corresponds to the normal-mode analysis of a linear system of differential equations.Copyright 1988 by the American Geophysical Union. Paper number 8D0305.0148-0227/88/008D-0305505.00The method described here represents the linearized form of the more general "principal interaction pattern" (PIP) technique for constructing simplified dynamical models to approximate complex nonlinear systems with many degrees of freedom [cf. Hasselmann, this issue]. In the present application, however, we emphasize the diagnostic rather than the dynamical aspects of the method. Thus we introduce a further simplification of the general technique in addition to the linearization. Rather than simultaneously seeking both the optimal linear model (i.e., the Markov system matrix) and the optimal vector subspace in which the model is to be constructed, in accordance with the general PIPs and POPs philosophy, we regard the vector subspace as given. We carry out a standard reduction of the number of variables by using a relatively small set of empirical orthogonal...

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“…The vertical properties of the kelvin waves are also investigated, which has not been done earlier by Pan et al (2011). The two-dimensional fast Fourier transform (2D-FFT; Hayashi, 1982) is used to spectrally analyse the temperature fluctuation data to obtain the dominant wavenumbers, periods and vertical wavelengths of the KW during this event, and also before and after the event. …”

Section: Introductionmentioning

confidence: 99%

Strong Kelvin wave activity observed during the westerly phase of QBO – a case study

Das

Chen

2013

Ann. Geophys.

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Temperature data from Global Positioning System based Radio Occultation (GPS RO) soundings of the Formosa Satellite mission 3/Constellation Observing System for Meteorology, Ionosphere and Climate (FORMOSAT-3/COSMIC or F-3/C) micro satellites have been investigated in detail to study the Kelvin wave (KW) properties during September 2008 to February 2009 using the two-dimensional Fourier transform. It is observed that there was strong KW activity during November and December 2008; large wave amplitudes are observed from above the tropopause to 40 km – the data limit of F-3/C. KW of wavenumbers E1 and E2 with time periods 7.5 and 13 days, dominated during this period and the vertical wavelengths of these waves varied from 12 to 18 km. This event is very interesting as the QBO during this period was westerly in the lower stratosphere (up to ~ 26 km) and easterly above, whereas, climatological studies show that KW get attenuated during westerlies and their amplitudes maximise during easterlies and westerly shears. In the present study, however, the eastward propagating KW crossed the westerly lower stratosphere as the vertical extent of the westerly wind regime was less than the vertical wavelengths of the KW. The waves might have deposited eastward momentum in the upper stratosphere at 26–40 km, thereby reducing the magnitude of the easterly wind by as much as 10 m s⁻¹. The outgoing long wave radiation (OLR) is also investigated and it is found that these KW are produced due to deep convections in the lower atmosphere

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Space-Time Spectral Analysis and its Applications to Atmospheric Waves

Abstract: Space-time spectral analysis methods and their applications to large-scale atmospheric waves are reviewed.

Cited by 217 publications

References 47 publications

Convectively Coupled Kelvin Waves in an Idealized Moist General Circulation Model

Convectively Coupled Kelvin Waves in an Idealized Moist General Circulation Model

Principal oscillation pattern analysis of the 30‐ to 60‐day oscillation in general circulation model equatorial troposphere

Strong Kelvin wave activity observed during the westerly phase of QBO – a case study

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