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Kariya, Japan

Aichi University of Education is a national university at Kariya, Aichi, Japan, founded in 1949. Wikipedia.

Taguchi M.,Aichi University of Education
Atmospheric Science Letters | Year: 2016

This study explores a possible connection between predictability variations of major stratospheric sudden warmings (MSSWs) during Northern winter and the geometry of the polar vortex. We compare 1-month hindcasts from 1979 to 2012 of the Japan Meteorological Agency to the Japanese 55-year Reanalysis data. Results show that error variations of medium range (≈14day) forecasts of 21 actual MSSWs do depend on the observed geometry of the polar vortex: the errors are larger for vortex split MSSWs when the polar vortex is highly stretched as characterized by a high aspect ratio and an amplified zonal wavenumber 2 component. © 2016 Royal Meteorological Society.

This study investigates the predictability of three major stratospheric sudden warmings (MSSWs) of the vortex split type: the Southern Hemisphere case in September 2002 and two Northern Hemisphere cases in January 2009 and February 1989. The author examines changes in the predictability of the MSSWs with lead time, as well as the connection of the predictability to lower-atmospheric features for pre- and post-MSSW periods. The Japan Meteorological Agency (JMA)'s 1-month ensemble hindcast (HC) experiment data are compared to the Japanese 25-year Reanalysis Project (JRA-25)/JMA Climate Data Assimilation System (JCDAS) data. For the pre-MSSW period, a strong predictability connection is observed among all three cases. Unsuccessful predictions of the MSSWs are characterized by an underestimation (or lack) of the enhanced wave activity in the lower stratosphere, which is further related to the strength and persistence of the uppertropospheric ridge and trough. The mean zonal wind profile in the upper troposphere is also important for the 2009 case. These results confirm the role of tropospheric wave forcing of the MSSWs in the context of predictability. The characteristic time scale for successful predictions is approximately 10 days-2 weeks, which roughly corresponds to the time scale of the tropospheric wave forcing. No ensemble member successfully predicts the MSSWs with lead times longer than the time scale. The predictability connection between the stratospheric and tropospheric anomalies is more subtle for the post-MSSW period. In particular, the HC group initialized about 1 week before the MSSWs tends to reproduce the evolution of the stratosphere after the MSSWs well but not that of the troposphere in some cases. © 2014 American Meteorological Society.

Taguchi M.,Aichi University of Education
Journal of Geophysical Research: Atmospheres | Year: 2010

Using a stratospheric zonal wind data archive of radiosonde observations at equatorial stations for 1953-2008, this study investigates whether or not signals of the quasi-biennial oscillation (QBO) vary with the El Niño-Southern Oscillation (ENSO) cycle. The signals of the QBO are represented by trajectories in a phase space spanned by time series of two leading modes of wind variability. Two properties of the trajectories, distance from the origin and time rate of change in argument, which are proxies for amplitude and phase progression rate of the QBO, respectively, are first examined in relation to seasons and QBO phases. The examination confirms known features of the QBO including the so-called seasonal locking and more regular phase propagation for the westerly phase. A further comparison of the properties between cold and warm ENSO conditions (La Niña and El Niño, respectively) reveals unprecedented evidence of clear variations of the QBO with ENSO: the QBO signals exhibit weaker amplitude and faster phase propagation for El Niño conditions. Such variations are also supported by a composite analysis of zonal wind anomalies. We also discuss a possible connection of the ENSO-associated changes in the QBO with those in equatorial wave activity. Copyright 2010 by the American Geophysical Union.

Taguchi M.,Aichi University of Education
Journal of the Atmospheric Sciences | Year: 2010

This study investigates ENSO-induced changes in the tropical lower stratosphere for northern winter as simulated by the Whole Atmosphere Community Climate Model (WACCM). A comparison is made between two 3650-day perpetual January experiments forced with La Niña-and El Niño-like sea surface temperature conditions over the equatorial Pacific. The present analysis includes an extension of the diagnostic framework used for the climatological annual cycle in Part I. A comprehensive description of the ENSO-induced changes, together with their heat and zonal momentum budget diagnoses, demonstrates that the changes are consistently characterized by cooling, locally accelerated Brewer-Dobson circulation (upwelling and poleward flow) and strengthened tropical/subtropical wave driving for the El Niño-like condition. The cooling broadly peaks near the equator with general hemispheric symmetry, and the strengthenings in the poleward flow and wave driving take place in both hemispheres. An important role in the strengthened wave driving is played by changes in tropical/subtropical stationary waves. The changes notably include a dumbbell-shaped height pattern over the Pacific or a modulation of equatorial Rossby waves in response to redistributed convective heating with the ENSO-like perturbation. © 2010 American Meteorological Society.

Mizutani U.,Nagoya Industrial Science Research Institute | Inukai M.,Toyota Technological Institute | Sato H.,Aichi University of Education | Zijlstra E.S.,University of Kassel
Chemical Society Reviews | Year: 2012

Full-potential linearized augmented plane wave (FLAPW) electronic band calculations were performed for two RT- (rhombic triacontahedron) and five MI- (Mackay icosahedron) type 1/1-1/1-1/1 approximants plus several complex metallic compounds in Al-TM (TM = transition metal element) binary alloy systems in order to elucidate the origin of a pseudogap from the viewpoint of Fermi surface-Brillouin zone (FsBz) interactions. The square of the Fermi diameter (2k F) 2 and square of the critical reciprocal lattice vector G 2 or the critical set of lattice planes, with which electrons at the Fermi level E F are interfering, can be extracted from the FLAPW-Fourier method. We revealed that a pseudogap in both RT- and MI-type 1/1-1/1-1/1 approximants universally originates from interference phenomenon satisfying the matching condition (2k F) 2 = G 2 equal to 50 in units of (2π/a) 2, where a is the lattice constant. The multi-zone effect involving not only G 2 = 50 but also its neighboring ones is also claimed to be responsible for constituting a pseudogap across E F. The value of e/a for Mn, Fe, Re and Ru elements in the periodic table is deduced to be positive in the neighborhood of unity. All 1/1-1/1-1/1 approximants, regardless of RT- or MI-type atomic cluster involved, are stabilized at around e/a= 2.7, while their counterpart quasicrystals are at around e/a= 2.2. A new Hume-Rothery electron concentration rule linking the number of atoms per unit cell, e/uc, with a critical G 2 holds well for all complex intermetallic compounds characterized by a pseudogap at E F. © 2012 The Royal Society of Chemistry.

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