Frontier Research Center for Global Change

Yokohama-shi, Japan

Frontier Research Center for Global Change

Yokohama-shi, Japan
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Nagashima T.,Japan National Institute of Environmental Studies | Sudo K.,Nagoya University | Sudo K.,Frontier Research Center for Global Change | Akimoto H.,Japan National Institute of Environmental Studies | And 2 more authors.
Atmospheric Chemistry and Physics | Year: 2017

The relative contributions of various source regions to the long-term (1980-2005) increasing trend in surface ozone (O3) over Japan were estimated by a series of tracer-tagging simulations using a global chemical transport model. The model simulated the observed increasing trend in surface O3, including its seasonal variation and geographical features, in Japan well and demonstrated the relative roles of different source regions in forming this trend. Most of the increasing trend in surface O3 over Japan (∼ 97 %) that was simulated was explained as the sum of trends in contributions of different regions to photochemical O3 production. The increasing trend in O3 produced in China accounted for 36 % of the total increasing trend and those in the other northeast Asian regions (the Korean Peninsula, coastal regions in East Asia, and Japan) each accounted for about 12-15 %. Furthermore, the contributions of O3 created in the entire free troposphere and in western, southern, and southeastern Asian regions also increased, and their increasing trends accounted for 16 and 7 % of the total trend, respectively. The impact of interannual variations in climate, in methane concentration, and in emission of O3 precursors from different source regions on the relative contributions of O3 created in each region estimated above was also investigated. The variation of climate and the increase in methane concentration together caused the increase of photochemical O3 production in several regions, and represented about 19 % of the total increasing trend in surface O3 over Japan. The increase in emission of O3 precursors in China caused an increase of photochemical O3 production not only in China itself but also in the other northeast Asian regions and accounted for about 46 % of the total increase in surface O3 over Japan. Similarly, the relative impact of O3 precursor emission changes in the Korean Peninsula and Japan were estimated as about 16 and 4 % of the total increasing trend, respectively. The O3 precursor emission change in regions other than northeast Asia caused increases in surface O3 over Japan mainly through increasing photochemical O3 production in western, southern, and southeast Asia and the free troposphere and accounted for about 16 % of the total. © 2017 Author(s).

Pattyn F.,Roosevelt University | Schoof C.,University of British Columbia | Perichon L.,Roosevelt University | Hindmarsh R.C.A.,Natural Environment Research Council | And 16 more authors.
Cryosphere | Year: 2012

Predictions of marine ice-sheet behaviour require models that are able to robustly simulate grounding line migration. We present results of an intercomparison exercise for marine ice-sheet models. Verification is effected by comparison with approximate analytical solutions for flux across the grounding line using simplified geometrical configurations (no lateral variations, no effects of lateral buttressing). Unique steady state grounding line positions exist for ice sheets on a downward sloping bed, while hysteresis occurs across an overdeepened bed, and stable steady state grounding line positions only occur on the downward-sloping sections. Models based on the shallow ice approximation, which does not resolve extensional stresses, do not reproduce the approximate analytical results unless appropriate parameterizations for ice flux are imposed at the grounding line. For extensional-stress resolving "shelfy stream" models, differences between model results were mainly due to the choice of spatial discretization. Moving grid methods were found to be the most accurate at capturing grounding line evolution, since they track the grounding line explicitly. Adaptive mesh refinement can further improve accuracy, including fixed grid models that generally perform poorly at coarse resolution. Fixed grid models, with nested grid representations of the grounding line, are able to generate accurate steady state positions, but can be inaccurate over transients. Only one full-Stokes model was included in the intercomparison, and consequently the accuracy of shelfy stream models as approximations of full-Stokes models remains to be determined in detail, especially during transients. © 2012 Author(s).

Neelin J.D.,University of California at Los Angeles | Lintner B.R.,University of California at Los Angeles | Lintner B.R.,Rutgers University | Tian B.,Jet Propulsion Laboratory | And 6 more authors.
Geophysical Research Letters | Year: 2010

Simple prototypes for forced advection-diffusion problems are known to produce passive tracer distributions that exhibit approximately exponential or stretched exponential tails. Having previously found an approximately exponential tail for the column integrated water vapor (CWV) distribution under high precipitation conditions, we conjectured that if such prototypes are relevant to more complex tropospheric tracer problems, we should find such tails for a wide set of tracers. Here it is shown that such tails are indeed ubiquitous in observed, model, and reanalysis data sets for a variety of tracers, either column integrated or averaged through a deep layer, including CO and CO2. The long tails in CWV are associated with vertical transport and can occur independent of a local precipitation sink. These non-Gaussian distributions can have consequences for source attribution studies of anthropogenic tracers, and for mechanisms of precipitation extremes; the properties of the tails may help constrain model tracer simulations. Copyright © 2010 by the American Geophysical Union.

Saikawa E.,Massachusetts Institute of Technology | Saikawa E.,Emory University | Prinn R.G.,Massachusetts Institute of Technology | Dlugokencky E.,National Oceanic and Atmospheric Administration | And 20 more authors.
Atmospheric Chemistry and Physics | Year: 2014

We present a comprehensive estimate of nitrous oxide (N2O) emissions using observations and models from 1995 to 2008. High-frequency records of tropospheric N2O are available from measurements at Cape Grim, Tasmania; Cape Matatula, American Samoa; Ragged Point, Barbados; Mace Head, Ireland; and at Trinidad Head, California using the Advanced Global Atmospheric Gases Experiment (AGAGE) instrumentation and calibrations. The Global Monitoring Division of the National Oceanic and Atmospheric Administration/Earth System Research Laboratory (NOAA/ESRL) has also collected discrete air samples in flasks and in situ measurements from remote sites across the globe and analyzed them for a suite of species including N2O. In addition to these major networks, we include in situ and aircraft measurements from the National Institute of Environmental Studies (NIES) and flask measurements from the Tohoku University and Commonwealth Scientific and Industrial Research Organization (CSIRO) networks. All measurements show increasing atmospheric mole fractions of N2O, with a varying growth rate of 0.1-0.7% per year, resulting in a 7.4% increase in the background atmospheric mole fraction between 1979 and 2011. Using existing emission inventories as well as bottom-up process modeling results, we first create globally gridded a priori N2O emissions over the 37 years since 1975. We then use the three-dimensional chemical transport model, Model for Ozone and Related Chemical Tracers version 4 (MOZART v4), and a Bayesian inverse method to estimate global as well as regional annual emissions for five source sectors from 13 regions in the world. This is the first time that all of these measurements from multiple networks have been combined to determine emissions. Our inversion indicates that global and regional N2O emissions have an increasing trend between 1995 and 2008. Despite large uncertainties, a significant increase is seen from the Asian agricultural sector in recent years, most likely due to an increase in the use of nitrogenous fertilizers, as has been suggested by previous studies. Copyright © 2014 by ASME.

Akter N.,Nagoya University | Akter N.,Bangladesh University of Engineering and Technology | Tsuboki K.,Bangladesh University of Engineering and Technology | Tsuboki K.,Frontier Research Center for Global Change
Monthly Weather Review | Year: 2012

Cyclone Sidr, one of the most devastating tropical cyclones that resulted in several thousand deaths and substantial damages, developed in the north Indian Ocean and made landfall over the Bangladesh coast on 15 November 2007. Observation and simulation results show that Sidr was embedded in a nonuniform environment and contained an intense outer rainband to the east of its center and a significant frontal band to the northwest. A detailed study of the outer rainband is performed by numerical simulation. The eastern band was a long, quasi-straight shape in the meridional direction that remained stationary relative to the cyclone center. This band was composed of convective cells that developed southeast of the center within a synoptic-scale convergence zone and propagated along the band toward the northeast quadrant. The speed of the downwind-propagating cells was greater than that of the cyclone, which resulted in a convective cluster northeast of the center. Only the downwind portion of the band consisted of convection with stratiform rain, whereas the upwind and middle portions contained active convective cells without stratiform rain. The band was located between the synoptic-scale flows of a weakly sheared, gradient-balanced westerly and a strongly sheared, nongradient-balanced prevailing southerly caused by the complex terrain of the Bay of Bengal's southeast region. Low-level convergence along the band was dominated by cross-band flow from both sides of the band and was confined below 3 km. As the cyclone moved northward, the convergence zone resulted in the extension of band length up to;800 km. The southerly at the eastern side of the center gradually accelerated and was directed toward the center by a strong pressure gradient force. The flow accumulated a substantial amount of water vapor from the sea in addition to the increased moisture in the lower troposphere, resulting in further intensification of the convective cells. © 2012 American Meteorological Society.

Nomura M.,Nagoya University | Tsuboki K.,Nagoya University | Tsuboki K.,Frontier Research Center for Global Change
Journal of the Meteorological Society of Japan | Year: 2012

Spiral bands are characteristic meso-beta-scale structures of typhoons in their mature stages. Observational study shows that spiral bands cause strong rainfall. The spiral bands are classified into two types: inner and outer rainbands. The inner rainband is formed near the typhoon center. In this study, we focus on the precipitation process in the inner rainband within the typhoon. Two neighboring spiral bands are often observed near the typhoon center. Previous studies have shown the mechanism of intensifying rainfall in the inner-side spiral band of two neighboring inner rainbands that frequently form in this region. However, the intensification of the outer-side spiral band of two neighboring inner rainbands has not been widely reported. Therefore, to clarify the mechanism of intensifying rainfall in the spiral bands, we focus on cloud microphysical processes and perform a numerical experiment using a cloud-resolving model. We show that cold rain processes are important for the intensification of precipitation in the spiral band. In particular, production and growth of graupel are the most effective processes for the intensification of precipitation in the spiral band. © 2012, Meteorological Society of Japan.

Nomura M.,Nagoya University | Tsuboki K.,Nagoya University | Tsuboki K.,Frontier Research Center for Global Change | Shinoda T.,Nagoya University
Journal of the Meteorological Society of Japan | Year: 2012

This study uses a cloud-resolving model to examine the impact of sedimentation of cloud ice on the cloud-top height and the precipitation intensity of typical precipitation systems in East Asia, including a typhoon, snow clouds over the Sea of Japan, and the Baiu front. The fall velocity of cloud ice is assumed to be 0.1 m s-1. When the sedimentation process of cloud ice is included in the model, the horizontal distribution and frequency of the cloud-top height show significantly better agreement with satellite observations. Furthermore, cloud ice with sedimentation concentrates at a lower level than that without sedimentation, and converts to snow and graupel by microphysical growth processes. More solid water substances located in the thin layer above the 0°C level contribute to intensification of precipitation at the surface by several percent, especially in the convective area. © 2012, Meteorological Society of Japan.

O'Ishi R.,University of Tokyo | O'Ishi R.,Japan National Institute of Polar Research | Abe-Ouchi A.,University of Tokyo | Abe-Ouchi A.,Frontier Research Center for Global Change
Climate of the Past | Year: 2013

When the climate is reconstructed from paleoevidence, it shows that the Last Glacial Maximum (LGM, ca. 21 000 yr ago) is cold and dry compared to the present-day. Reconstruction also shows that compared to today, the vegetation of the LGM is less active and the distribution of vegetation was drastically different, due to cold temperature, dryness, and a lower level of atmospheric CO2 concentration (185 ppm compared to a preindustrial level of 285 ppm). In the present paper, we investigate the influence of vegetation change on the climate of the LGM by using a coupled atmosphere-ocean-vegetation general circulation model (AOVGCM, the MIROC-LPJ). The MIROC-LPJ is different from earlier studies in the introduction of a bias correction method in individual running GCM experiments. We examined four GCM experiments (LGM and preindustrial, with and without vegetation feedback) and quantified the strength of the vegetation feedback during the LGM. The result shows that global-averaged cooling during the LGM is amplified by +13.5 % due to the introduction of vegetation feedback. This is mainly caused by the increase of land surface albedo due to the expansion of tundra in northern high latitudes and the desertification in northern middle latitudes around 30° N to 60° N. We also investigated how this change in climate affected the total terrestrial carbon storage by using offline Lund-Potsdam-Jena dynamic global vegetation model (LPJ-DGVM). Our result shows that the total terrestrial carbon storage was reduced by 597 PgC during the LGM, which corresponds to the emission of 282 ppm atmospheric CO2. In the LGM experiments, the global carbon distribution is generally the same whether the vegetation feedback to the atmosphere is included or not. However, the inclusion of vegetation feedback causes substantial terrestrial carbon storage change, especially in explaining the lowering of atmospheric CO2 during the LGM. © Author(s) 2013.

Akter N.,Nagoya University | Tsuboki K.,Nagoya University | Tsuboki K.,Frontier Research Center for Global Change
Scientific Online Letters on the Atmosphere | Year: 2010

Cyclone Sidr had an intense rainband east of the cyclone center. The rainband exhibited two strong convective lines (band axes) composed of convective cells. To study the characteristics of the convective cells, a simulation was performed at 1-km resolution by using a cloud-resolving model. In both band axes, some cells showed the characteristic structure of a supercell. Supercells within the outer axis had stronger updraft, more intense precipitation, and a longer lifetime than those of the inner axis. The values of the CAPE and helicity are different in the strong vertical shear environment of the inner and outer axes. A large moisture flux was present throughout the troposphere on the east side of the outer axis. On the other hand, the upper level west of the inner axis was relatively dry. These are additional factors affecting the differences in cell characteristics in the two band axes. © 2010, the Meteorological Society of Japan.

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