Analysis of summertime atmospheric transport of fine particulate matter in Northeast Asia   总被引：1，自引：0，他引：1  

Hikari Shimadera  Hiroshi Hayami  Yu Morino  Toshimasa Ohara  Satoru Chatani  Shuichi Hasegawa  Naoki Kaneyasu 《Asia-Pacific Journal of Atmospheric Sciences》2013,49(3):347-360

In Northeast Asia, the effect of long-range transport of air pollutants is generally pronounced in spring and winter, but can be important even in summer. This study analyzed summer-time atmospheric transport of elemental carbon (EC) and sulfate (SO₄ ^2?) with the Community Multiscale Air Quality (CMAQ) model driven by the Weather Research and Forecasting (WRF) model. The WRF/CMAQ modeling system was applied to regions ranging from Northeast Asia to the Greater Tokyo Area in Japan in summer 2007. In terms of EC, while the model simulated well the effect of long-range transport, the simulation results indicated that domestic emissions in Japan dominantly contributed (85%) to EC concentrations in the Greater Tokyo. In terms of SO₄ ^2?, the simulation results indicated that both domestic emissions (62%) and long-range transport from the other countries (38%) substantially contributed to SO₄ ^2? concentrations in the Greater Tokyo. Distinctive transport processes of SO₄ ^2? were associated with typical summer-time meteorological conditions in the study region. When a Pacific high-pressure system covered the main island of Japan, domestic emissions, including volcanic emission, dominantly contributed to SO₄ ^2? concentrations in the Greater Tokyo. When a high-pressure system prevailed over the East China Sea and low-pressure systems passed north of Japan, synoptic westerly winds associated with this pressure pattern transported a large amount of SO₄ ^2? from the continent to Japan. In addition, although heavy precipitation and strong wind decreased SO₄ ^2? concentrations near the center of a typhoon, peripheral typhoon winds occasionally played an important role in long-range transport of SO₄ ^2?.  相似文献   

Inverse estimation of empirical parameters used in a regional ocean circulation model     

Naoki Hirose 《Journal of Oceanography》2011,67(3):323-336

Significant impacts of the subgridscale parameterizations have been emphasized in modeling the ocean circulations, but various different parameter values are applied to similar numerical studies often without any justification. This study objectively estimates a set of empirical parameters along with their uncertainty for circulation modeling of the East Asian Marginal Seas. The solutions for 14 major parameters are obtained by using model Green’s functions with constraints of climatological temperature and salinity data. The largest cost function reduction occurs in the eastern Japan Sea associated with the sharp gradient of the Polar Front. The calibrated parameters are also validated with realistic transport and path of the Kuroshio in the final experiment. The inverse estimation shows that freshwater discharges from small rivers can be attributed to the coastal precipitation over a strip of land 74–81 km wide. The thickness diffusion coefficient may be similar to the isopycnal and horizontal diffusion coefficients in their magnitude. The accelerated initial condition also contributes to the cost function reduction resulting in weaker trends of deep temperature. Most importantly, estimated scaling factors suggest a significant reduction of the reanalyzed wind stress data for more realistic ocean circulations. Possible reasons for the momentum missing are also discussed.  相似文献   

Searching for massive clusters in weak lensing surveys     

Takashi Hamana  Masahiro Takada  Naoki Yoshida 《Monthly notices of the Royal Astronomical Society》2004,350(3):893-913

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Japanese VLBI Network Observations of a Gamma-Ray Narrow-Line Seyfert 1 Galaxy 1H 0323+342     

Kiyoaki?WajimaEmail author  Kenta?Fujisawa  Masaaki?Hayashida  Naoki?Isobe 《Journal of Astrophysics and Astronomy》2014,35(3):215-218

We made simultaneous single-dish and VLBI observations of a gamma-ray narrow-line Seyfert 1 (NLS1) galaxy 1H 0323+342. We found significant flux variation at 8 GHz on a time scale of one month. The total flux density varied by 5.5% in 32 days, corresponding to a variability brightness temperature of 7.0 × 10¹¹ K. We also obtained brightness temperatures of greater than 5.2 × 10¹⁰ K from the VLBI images. These high brightness temperatures suggest that the source has nonthermal processes in the central engine. The source structure could be modelled by two elliptical Gaussian components on the parsec scales. The flux of the central component decreases in the same way as the total flux density, showing that the short-term variability is mainly associated with this component.  相似文献   

Estimation of mean residence times of subsurface waters using seasonal variation in deuterium excess in a small headwater catchment in Japan     

Naoki Kabeya  Masanori Katsuyama  Masatoshi Kawasaki  Nobuhito Ohte  Atsuko Sugimoto 《水文研究》2007,21(3):308-322

We measured deuterium excess (d = δD ? 8δ¹⁸O) in throughfall, groundwater, soil water, spring water, and stream water for 3 years in a small headwater catchment (Matsuzawa, 0·68 ha) in the Kiryu Experimental Watershed in Japan. The d value represents a kinetic effect produced when water evaporates. The d value of the throughfall showed a sinusoidal change (amplitude: 6·9‰ relative to Vienna standard mean ocean water (V‐SMOW)) derived from seasonal changes in the source of water vapour. The amplitude of this sinusoidal change was attenuated to 1·3–6·9‰ V‐SMOW in soil water, groundwater, spring water, and stream water. It is thought that these attenuations derive from hydrodynamic transport processes in the subsurface and mixing processes at an outflow point (stream or spring) or a well. The mean residence time (MRT) of water was estimated from d value variations using an exponential‐piston flow model and a dispersion model. MRTs for soil water were 0–5 months and were not necessarily proportional to the depth. This may imply the existence of bypass flow in the soil. Groundwater in the hillslope zone had short residence times, similar to those of the soil water. For groundwater in the saturated zone near the spring outflow point, the MRTs differed between shallow and deeper groundwater; shallow groundwater had a shorter residence time (5–8 months) than deeper groundwater (more than 9 months). The MRT of stream water (8–9 months) was between that of shallow groundwater near the spring and deeper groundwater near the spring. The seasonal variation in the d value of precipitation arises from changes in isotopic water vapour composition associated with seasonal activity of the Asian monsoon mechanism. The d value is probably an effective tracer for estimating the MRT of subsurface water not only in Japan, but also in other East Asian countries influenced by the Asian monsoon. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

First sources in infrared light: stars, supernovae and miniquasars     

Asantha Cooray  Naoki Yoshida 《Monthly notices of the Royal Astronomical Society》2004,351(3):L71-L77

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Giant cluster arcs as a constraint on the scattering cross-section of dark matter     

Massimo Meneghetti  Naoki Yoshida  Matthias Bartelmann  Lauro Moscardini  Volker Springel  Giuseppe Tormen  Simon D. M. White 《Monthly notices of the Royal Astronomical Society》2001,325(1):435-442

We carry out ray tracing through five high-resolution simulations of a galaxy cluster, to study how its ability to produce giant gravitationally lensed arcs is influenced by the collision cross-section of its dark matter. In three cases typical dark matter particles in the cluster core undergo between 1 and 100 collisions per Hubble time; two more explore the long ('collisionless') and short ('fluid') mean free path limits. We study the size and shape distributions of arcs and compute the cross-section for producing 'extreme' arcs of various sizes. Even a few collisions per particle modifies the core structure enough to destroy the ability of the cluster to produce long, thin arcs. For larger collision frequencies the cluster must be scaled up to unrealistically large masses before it regains the ability to produce giant arcs. None of our models with self-interacting dark matter (except the 'fluid' limit) is able to produce radial arcs; even the case with the smallest scattering cross-section must be scaled to the upper limit of observed cluster masses before it produces radial arcs. Apparently the elastic collision cross-section of dark matter in clusters must be very small, below 0.1 cm² g⁻¹, to be compatible with the observed ability of clusters to produce both radial arcs and giant arcs.  相似文献   

Numerical experiment for strontium-90 and cesium-137 in the Japan Sea     

Hideyuki Kawamura  Toshimichi Ito  Takuya Kobayashi  Shigeyoshi Otosaka  Naoki Hirose  Orihiko Togawa 《Journal of Oceanography》2010,66(5):649-662

A numerical experiment is carried out to reproduce distribution of concentration of ⁹⁰Sr and ¹³⁷Cs, estimate their total amount and verify their source in the Japan Sea. Model results are in good agreement with observational findings in the Japan Sea expeditions between 1997 and 2002 by the Japan Atomic Energy Agency. Vertical profiles of the concentration of ⁹⁰Sr and ¹³⁷Cs show exponential decreases with depth from the sea surface to the sea bottom. From the model and observational results, it is suggested that the concentration of ⁹⁰Sr and ¹³⁷Cs in the surface layer is approximately in the range of 1.0–1.5 Bq/m³ and 2.0–2.5 Bq/m3, respectively. On the other hand, it is found that the concentration in the intermediate and deep layer is higher than that observed in the northwestern Pacific Ocean, suggesting active winter convection in the Japan Sea. The total amount of ⁹⁰Sr and ¹³⁷Cs in the seawater is evaluated to be 1.34 × 10¹⁵ Bq and 2.02 × 10¹⁵ Bq, respectively, in the numerical experiment, which demonstrates an estimation by observational data obtained in the Japan Sea expeditions. The total amount of ⁹⁰Sr and ¹³⁷Cs changed during the second half of 20th century corresponding to deposition at the sea surface with the maximums of 4.86 × 10¹⁵ Bq for ⁹⁰Sr and 7.33 × 10¹⁵ Bq for ¹³⁷Cs, respectively, in the mid-1960s. The numerical experiment suggests that the main source of ⁹⁰Sr and ¹³⁷Cs has been global fallout, although there have been some potential sources in the Japan Sea.  相似文献   

Effect of the along-strait wind on the volume transport through the Tsushima/Korea Strait in September     

Jae-Hong Moon  Naoki Hirose  Jong-Hwan Yoon  Ig-Chan Pang 《Journal of Oceanography》2009,65(1):17-29

Recent investigation suggests that volume transport through the Tsushima/Korea Strait often has double peaks during the summer to autumn period with decreasing transport in September. The satellite-observed wind changes from weak northwestward (across-strait) in summer to strong southwestward (along-strait) in early autumn (September) in the strait. Such a strong along-strait wind is related to tropical cyclones, which frequently pass through the East China Sea in September. The effect of the along-strait wind component on the transport variation is examined using a three-dimensional numerical model. The simulated volume transport through the Tsushima/Korea Strait shows realistic seasonal and intra-seasonal variations. According to sensitivity experiments on local winds, the transport variations in September are mainly generated by strong along-strait (southwestward) wind rather than weak across-strait wind. The strait transport responds to the along-strait wind (southeastward), which produces a sea level increase along the Korean coast, resulting in the geostrophic balance across the strait. The transport minimum through the Tsushima/Korea Strait in September can be determined by the combination of the across-strait geostrophic and along-strait ageostrophic balances. The Editor-in-Chief does not recommend the usage of the term “Japan/East Sea” in place of “Sea of Japan”.  相似文献   

The 21-cm signature of early relic H ii regions     

Midori Tokutani  Naoki Yoshida  S. Peng Oh  Naoshi Sugiyama 《Monthly notices of the Royal Astronomical Society》2009,395(2):777-780

We calculate the spin temperature and 21-cm brightness of early H  ii regions around the first stars. We use outputs from cosmological radiation-hydrodynamics simulations of the formation and evolution of early H  ii regions. In the pre-re-ionization era, H  ii regions around massive primordial stars have diameters of a few kpc. The gas within the H  ii regions is almost fully ionized, but begins recombining after the central stars die off. The relic H  ii regions are then seen as bright emission sources in hydrogen 21 cm. We make brightness temperature maps of the H  ii regions, accounting for radiative coupling with Lyman α photons in a simplified manner. The spin temperature in the relic H  ii region is close to the gas kinetic temperature, generally several hundred to several thousand degrees. We show that the relic H  ii region can be as bright as  δ T _b∼ 100 mK  in differential temperature against the cosmic microwave background for an angular resolution of subarcseconds. While individual early H  ii patches will not be identified by currently planned radio telescopes, the collective fluctuations from early H  ii regions might imprint signatures in the 21-cm background.  相似文献