Analysis of Recent Extreme Events Measured by the Barotropic Component of the Atmosphere

Tanaka, Hiroshi; Matsueda, Mio

doi:10.2151/jmsj.2004.1281

Cited by 5 publications

(6 citation statements)

References 35 publications

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“…The dynamical understanding of those low-frequency variabilities with barotropic nature may be the central subject for the long-range weather forecasting and the extreme events. Although there are many studies which suggest that AO is a statistical mode, and North Atlantic Oscillation (NAO) is a physical mode (e.g., Deser 2000; Ambaum et al 2001;Itoh 2002;Christensen 2002), we find in our latest study that the dynamical eigenmode of the atmosphere supports the structure of the AO as the dynamical reality of the atmosphere (Tanaka and Matsueda 2005). According to the analysis of the barotropic component by Tanaka and Matsueda (2004), more than 80% of the recent extreme events are associated with the natural variability of the atmosphere under non-extreme external forcing.…”

Section: Introductionsupporting

confidence: 40%

“…The analysis method is based on the barotropic P-model described in Tanaka and Nohara (2001) where the external forcing of the barotropic model is evaluated from observations as a residual of the governing equation.…”

Section: Methodsmentioning

confidence: 99%

“…The right-hand side represents a nonlinear term vector N and a diabatic term vector F, which includes the zonal and meridional components of frictional forces and a diabatic heating rate. Refer to Tanaka (1998) for the definition of variables. In order to obtain a system of 3-D spectral primitive equations, we expand the vectors U and F in 3-D normal mode functions.…”

Section: Methodsmentioning

confidence: 99%

“…As discussed by Tanaka and Matsueda (2004), total energy E of the atmosphere (sum of kinetic energy and available potential energy) is simply the sum of the energy elements E i defined by:…”

Section: Methodsmentioning

confidence: 99%

“…It has been well known that most of the low-frequency variability of the atmosphere such as a blocking high, Arctic Oscillation (AO) and PNA-like teleconnections are characterized by their barotropic structure (Wallace and Blackmon 1981;Wallace and Gutzler 1981;Thompson and Wallace 1998;Tanaka 1998Tanaka , 2003. The barotropic component of the atmosphere is dynamically unique in that it consists of an isolated discrete spectrum with respect to the vertical normal mode, while all other baroclinic components construct a continuous spectrum (Staniforth et al 1985).…”

Section: Introductionmentioning

confidence: 99%

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EOF and SVD Analyses of the Low-Frequency Variability of the Barotropic Component of the Atmosphere

Matsueda

Tanaka

2005

Journal of the Meteorological Society of Japan

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In this study, we have investigated the dominant horizontal patterns of the barotropic component of the atmosphere, the external forcing to it, and the nonlinear scale interactions, using the EOF and SVD analyses for 50 years of DJF mean NCEP/NCAR reanalysis. According to the EOF analysis, the horizontal pattern of the EOF-1 of the atmosphere represents the Arctic Oscillation (AO), and the EOF-2 represents the PNA teleconnection pattern. The SVD-1 for the barotropic component and the external forcing represents the structure of AO with the external forcing characterized by topographic forcing. The energy balance for the SVD patterns, however, shows that the external forcing of the SVD-1 damps the AO-like anomaly of the barotropic component. The SVD-2 represents the PNA, and the time series of the coefficient indicates a link with El Niñ o/La Niñ a. The external forcing of the SVD-2 appears also to damp the PNA-like anomaly. Furthermore, the SVD-1 for the barotropic component and the nonlinear scale interactions represents the AO-like anomaly with the large nonlinear scale interactions over half of the Northern Hemisphere. The energy balance for this SVD pattern shows that the nonlinear scale interactions excite the AO-like anomaly. Similarly, the SVD-2 shows the energy increase by the nonlinear scale interactions the same as SVD-1. The nonlinear scale interactions are further decomposed in linear interactions with the climate basic state and the reminder. We find by the energetics analysis that the AO-like anomaly is mostly excited by the interactions with the basic state.It is concluded from the SVD analyses that the extreme events associated with low-frequency variabilities are not induced by the low-frequency forcing, but mostly by the energy supply from the climate basic state.

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