Shigenori Murakami

Meteorological Research Institute, Japan Meteorological Agency, Ibaragi, Ōsaka, Japan

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Publications (7)22.15 Total impact

  • Shigenori Murakami
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    ABSTRACT: A new diagnostic scheme for the atmospheric local energetics is proposed. In contrast to conventional schemes, this scheme correctly represents the local features of the Lorenz energy cycle for time-mean and transient-eddy fields. The key point is that the energy equation is divided not into two but into three parts consisting of the mean, eddy, and interaction energy equations, when basic variables are divided into mean and eddy fields. The interaction energy itself vanishes when appropriate averaging is taken. However, the equation for interaction energy does not vanish and gives a relationship between the interaction energy flux and the two types of energy conversion terms. These three quantities give the complete information for the energy interactions between mean and eddy fields. The Lorenz energy diagram is reconstructed to include a representation of this relationship. A brief discussion about the relationship with wave activity analysis is also given.
    No preview · Article · Apr 2011 · Journal of the Atmospheric Sciences
  • Shigenori Murakami · Rumi Ohgaito · Ayako Abe-Ouchi
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    ABSTRACT: The atmospheric local energy cycle in the LastGlacialMaximum(LGM) climate simulated by an atmosphere-ocean GCM (AOGCM) is investigated using a new diagnostic scheme. In contrast to existing ones, this scheme can represent the local features of the Lorenz energy cycle correctly, and it provides the complete information about the three-dimensional structure of the energy interactions between mean and eddy fields. The diagnosis reveals a significant enhancement of the energy interactions through the barotropic processes in the Atlantic sector at the LGM. Energy interactions through the baroclinic processes are also enhanced in theAtlantic sector, although those in the Pacific sector are rather weakened. These LGMresponses, however, are not evident in the global energy cycle except for an enhancement of the energy flow through the stationary eddies.
    No preview · Article · Mar 2011 · Journal of the Atmospheric Sciences
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    ABSTRACT: Three coupled atmosphere-ocean general circulation model (AOGCM) simulations of the Last Glacial Maximum (I-GM: about 21000 yr before present), conducted under the protocol of the second phase of the Paleoclimate Modelling Intercomparison Project (PMIP2), have been analyzed from a viewpoint of large-scale energy and freshwater balance. Atmospheric latent heat (LH) transport decreases at most latitudes due to reduced water vapour content in the lower troposphere. and dry static energy (DSE) transport in northern midlatitudes increases and changes the intensity contrast between the Pacific and Atlantic regions due to enhanced stationary waves over the North American ice Sheets. In low latitudes. even with an intensified Hadley circulation in the Northern Hemisphere (NH), reduced DSE transport by the mean zonal circulation as well as a reduced equatorward LH transport is observed. The oceanic heat transport at NH midlatitudes increases owing to intensified subpolar gyres, and the Atlantic heat transport at low latitudes increases in all models whether or not meridional overturning circulation (MOC) intensifies. As a result, total poleward energy transport at the LGM increases in NH mid- and low latitudes in all models. Oceanic freshwater transport decreases. compensating for the response of the atmospheric water vapor transport. These responses in the atmosphere and ocean make the northern North Atlantic Ocean cold and relatively fresh. and the Southern Ocean relatively warm and saline. This is a common and robust feature in all odels. The resultant ocean densities and ocean MOC response. however. show model dependency.
    Preview · Article · Oct 2008 · Journal of Climate
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    Akio Kitoh · Tatsuo Motoi · Shigenori Murakami
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    ABSTRACT: Modulation of El Niño-Southern Oscillation at the mid-Holocene [6000 yr before present (6 ka)] is investigated with a coupled ocean-atmosphere general circulation model. The model is integrated for 300 yr with 6-ka and present (0 ka) insolation both with and without flux adjustment, and the effect of flux adjustment on the simulation of El Niho is investigated. The response in the equatorial Pacific Ocean in 6 ka is in favor of weaker El Niño variability resulting from lowered sea surface temperature (SST) and a more diffuse thermocline. Atmospheric sensitivity in 6 ka is larger than that in 0 ka because of increased trade winds, while oceanic sensitivity in 6 ka is weaker than that in 0 ka, resulting from destabilization of the upper ocean, both in the flux- and non-flux-adjusted experiments. However, the use of flux adjustment causes a difference in the total response. El Niño variability in 6 ka does not change much from that in 0 ka with the flux-adjusted case, while the 6-ka El Niño variability is eaker without flux adjustment. Because the observed proxy data suggest weaker El Niño variability in the mid-Holocene, the non-flux-adjusted version gives a more reasonable response despite a larger bias in its basic states, implying that nondistortion of sensitivity to forcing is more important.
    Preview · Article · Jun 2007 · Journal of Climate
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    Shigenori Murakami · Akio Kitoh
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    ABSTRACT: A simple one-dimensional (1-D) climate model in the meridional direction is considered based on the maximum entropy production hypothesis. This model calculates latitudinal distribution of the emitted long-wave radiation and meridional heat transport for a given latitudinal distribution of the absorbed solar radiation.By treating the problem analytically, an Euler–Lagrange equation and a numerical method solving it are obtained. Calculations based on the maximum entropy production hypothesis qualitatively explain an enhancement of the poleward heat transport observed in a last glacial maximum simulation with a coupled general-circulation model. Copyright © 2005 Royal Meteorological Society
    Preview · Article · Dec 2006 · Quarterly Journal of the Royal Meteorological Society
  • Akio Kitoh · Shigenori Murakami
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    ABSTRACT: Simulations for the mid-Holocene (6000 years before present: 6 ka) and the Last Glacial Maximum (LGM: 21 ka) have been performed by a global ocean-atmosphere coupled general circulation model (GCM). After the initial spin-up periods, both runs were integrated for about 200 years. For 6 ka the model shows an enhanced seasonal variation in surface temperature and a northward shift of the African and the Indian summer monsoon rain area. Overall circulation features in the tropics correspond to a strong Walker circulation state with negative sea surface temperature (SST) and precipitation anomalies in the central Pacific and positive precipitation anomalies over the Indian and Australian monsoon regions. It is noted that there is about a 0.35°C cooling of the global mean SST. In contrast to the 6 ka result, the simulated tropical climate anomaly at 21 ka corresponds to a weak Walker circulation state. The simulated LGM SST decrease is about 2°C over the tropical western Pacific. It is larger (about 5°C) over the Caribbean Sea. This SST anomaly is in broad agreement with the observed proxy data. Interestingly, the model simulates a warmer than present SST over the subtropical Pacific. This may be related to a weaker subtropical anticyclone due to weakened monsoon circulation at the LGM.
    No preview · Article · Sep 2002 · Paleoceanography
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    Akio Kitoh · Shigenori Murakami · Hiroshi Koide
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    ABSTRACT: A simulation of the Last Glacial Maximum (LGM) climate has been performed by a global coupled atmosphere-ocean general circulation model (AOGCM). Two simulations are conducted for the LGM with different initial conditions: one with the present-day initial condition and the other with a pre-conditioning of fresh water flux over the North Atlantic. After more than 200 year integration both LGM simulations attained a similar quasi-equilibrium state. The global mean surface air temperature dropped 3.9 • C and precipitation decreased 11% compared to the present day simulation. The sea surface temperature dropped 1.7 • C in the tropics, with larger decreases in the Atlantic than in the Indo-Pacific. There is a region with warmer than present sea surface temperatures over the subtropical eastern Pa-cific. The thermohaline circulation in the North Atlantic in the LGM simulation is slightly stronger than in the present day simulation.
    Preview · Article · Jun 2001

Publication Stats

211 Citations
22.15 Total Impact Points

Institutions

  • 2001-2011
    • Meteorological Research Institute, Japan Meteorological Agency
      Ibaragi, Ōsaka, Japan
  • 2006-2008
    • Japan Agency for Marine-Earth Science Technology
      Kawasaki Si, Kanagawa, Japan