Construction and Characterization of an Atmospheric Simulation Smog Chamber   总被引：11，自引：0，他引：11  

武山  吕子峰  郝吉明  赵喆  李俊华 《大气科学进展》2007,24(2):250-258

Currently, air pollution in Beijing has become a complex problem with two types of source pollutants： coal smoke and photochemical smog. Furthermore the maximum hourly mean concentration of O3 increases continuously, especially in the summer. In order to simulate the photochemical reaction, develop an air quality simulation model and further improve the air quality of Beijing, a precisely temperature-controlled, indoor, smog chamber facility was designed and constructed at Tsinghua University. Characterization experiments have been carried out to acquire the basic parameters of the smog chamber, such as the wall loss rates of NO2, NO, O3, C3H6 and particulate matter （PM）, the intensity of ultraviolet （UV） light in the chamber, the reactivity of the purified air and the reproducibility of the experimental results. The results indicate that the facility performs up to specifications, and can meet the demands required for simulating the photochemical reaction. The effect of high primary contaminated PM on the formation of ozone and secondary organic aerosol （SOA） is under investigation.  相似文献   

Submarine flank eruption preceding caldera subsidence during the 2000 eruption of Miyakejima Volcano, Japan     

Takayuki Kaneko  Atsushi Yasuda  Taketo Shimano  Setsuya Nakada  Toshitsugu Fujii  Toshihiko Kanazawa  Azusa Nishizawa  Yoshihiro Matsumoto 《Bulletin of Volcanology》2005,67(3):243-253

During the early part of a seismic swarm preceding eruption and caldera formation at Miyakejima Volcano, discoloured sea surfaces were observed 1.5 km off the western coast of Miyakejima on 27 June 2000. A later survey of the area using a multi-beam side scan sonar and a remotely operated small submarine revealed four craters of 20–30 m diameter aligned east-west in a 100×10–30 m area on the seafloor, with hot water at 140°C being released from one of the centres. Each crater consists of submarine spatter overlain in part by scoria lapilli. Dredged spatter from the craters was fresh, and there was no evidence of activity of marine organisms on the spatter surface, indicating that the discoloured sea surface resulted from magmatic eruption on the seafloor. This eruption occurred when a westward-propagating seismic swarm, initiated beneath Miyakejimas summit, passed through the area. Finding new magma on the seafloor demonstrates that this seismic swarm was associated with intruding magma, moving outward from beneath Miyakejima. Submarine spatter shows flattened shapes with a brittle crust formed by cooling in water, and its composition is aphyric andesite of 54 wt% SiO₂. The spatter is similar in whole rock and mineral composition to spatter erupted in 1983. However, the wide range of Cl in melt inclusions in plagioclase of the 27 June submarine spatter shows that it is not simply a remnant of the 1983 magma, which has only high Cl melt inclusions in plagioclase. The mixed character of melt inclusions suggests involvement of a magma with low Cl melt inclusions. The magma erupted explosively on 18 August from Miyakejimas summit, considered as the second juvenile magma in this eruption, contains low Cl melt inclusions in plagioclase. Based on these observations and the eruption sequence, we present the following model: (1) A shallow magma chamber was filled with a remnant of 1983 magma that had evolved to a composition of 54–55 wt% SiO₂. (2) Injection of the 18 August magma into this chamber generated a mixed magma having a wide range of Cl in melt inclusions contained plagioclase. The magma mixing might have occurred shortly before the submarine eruption and could have been a trigger for the initiation of the removal of magma from the chamber as an extensive dyke, which eventually led to caldera subsidence.Editorial responsibility: S Nakada, T Druitt  相似文献   

Errata: Structure of Subsurface Intrusion of the Oyashio Water into the Kuroshio Extension and Formation Process of the North Pacific Intermediate Water     

Kuniaki Okuda  Ichiro Yasuda  Yutaka Hiroe  Yugo Shimizu 《Journal of Oceanography》2001,57(4):495-497

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Absolute Volume Transports of the Oyashio Referred to Moored Current Meter Data Crossing the OICE     

Kazuyuki Uehara  Shin-Ichi Ito  Hideo Miyake  Ichiro Yasuda  Yugo Shimizu  Tomowo Watanabe 《Journal of Oceanography》2004,60(2):397-409

During November 2000–June 2002, both direct current measurements from deployment of a line of five moorings and repeated CTD observations were conducted along the Oyashio Intensive observation line off Cape Erimo (OICE). All the moorings were installed above the inshore-side slope of the Kuril-Kamchatka Trench. Before calculating the absolute volume transports, we compared vertical velocity differences of relative geostrophic velocities with those of the measured velocities. Since both the vertical velocity differences concerned with the middle three moorings were in good agreement, the flows above the continental slope are considered to be in thermal wind balance. We therefore used the current meter data of these three moorings, selected among all five moorings, to estimate the absolute volume transports of the Oyashio referred to the current meter data. As a result, we estimated that the southwestward absolute volume transports in 0–1000 db are 0.5–12.8 × 10⁶ m³/sec and the largest transport is obtained in winter, January 2001. The Oyashio absolute transports in January 2001, crossing the OICE between 42°N and 41°15′ N from the surface to near the bottom above the continental slope, is estimated to be at least 31 × 10⁶ m³/sec. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Analytical Study of Longitudinal Mass Flux Due to the Shear Effect in a Tidal Basin     

Hidekazu Yasuda 《Journal of Oceanography》2004,60(3):587-596

The fundamental nature of the mass flux due to the shear effect is examined analytically in a basin with steady and oscillatory currents to promote a better understanding of the mass transport process in coastal waters. The currents are given from solutions of the simplified motion equation so as to be consistent with the diffusion equation. The matter concentration used is given by an analytical solution of the diffusion equation with the settling flux term contained. Mass flux, yielding the depth-averaged dispersion coefficient, is rather varied vertically in both steady and oscillatory currents. In the oscillatory current with a Stokes layer in particular, the vertical profile of flux is more complicated and even negative flux is induced near the basin floor. This negative flux does not necessarily yield a negative value of the vertically averaged dispersion coefficient. The exact dispersion coefficient given by the flux analysis is realized only in the steady state of the matter concentration distribution, though we can scarcely observe the steady state in the actual sea. The vertically uniform longitudinal dispersion coefficient at the stationary stage is shown to be caused from the vertical complexity of mass flux by the action of the vertical diffusing and the settling flux. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Longitudinal dispersion due to the boundary layer in an oscillatory current: Theoretical analysis in the case of an instantaneous line source     

Hidekazu Yasuda 《Journal of Oceanography》1983,38(6):385-394

The longitudinal dispersion effect due to the boundary layer formed by a tidal oscillatory current is examined theoretically. This analysis reveals the process whereby the dispersion coefficient becomes steady after the release of the diffusing substance. Though the dispersion due to an oscillatory current has so far been investigated mostly in the case of a linear velocity profile, the following result was found by taking account of the boundary layer in the oscillatory current. The depth-averaged dispersion coefficient for the case of a current having a boundary layer can be a few times larger than in the case of a linear velocity profile when the characteristic mixing time is long; the phase lead in the boundary layer induces nearly 20 percent of the longitudinal dispersion effect.  相似文献   

Two-dimensional asymmetric vortex merger: Contour dynamics experiment   总被引：1，自引：0，他引：1  

Ichiro Yasuda  Glenn R. Flierl 《Journal of Oceanography》1995,51(2):145-170

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Characteristics of SSH Anomaly Based on TOPEX/POSEIDON Altimetry and in situ Measured Velocity and Transport of Oyashio on OICE     

Shin-Ichi Ito  Kazuyuki Uehara  Takashi Miyao  Hideo Miyake  Ichiro Yasuda  Tomowo Watanabe  Yugo Shimizu 《Journal of Oceanography》2004,60(2):425-437

An observation line along the TOPEX/POSEIDON (T/P) ground track 060 was set to estimate the Oyashio transport. We call this line the OICE (Oyashio Intensive observation line off-Cape Erimo) along which we have been conducting repeated hydrographic observations and maintaining mooring systems. T/P derived sea surface height anomaly (SSHA) was compared with velocity and transport on OICE. Although the decorrelation scale of SSHA was estimated at about 80–110 km in the Oyashio region, the SSHA also contains horizontal, small-scale noise, which was eliminated using a Gaussian filter. In the comparison between the SSHA difference across two selected points and the subsurface velocity measured by a moored Acoustic Doppler Current Profiler (ADCP), the highest correlation (0.92) appeared when the smoothing scale was set at 30 km with the two points as near as possible. For the transport in the Oyashio region, the geostrophic transport between 39°30′ N and 42°N was compared with the SSHA difference across the same two points. In this case the highest correlations (0.79, 0.88 and 0.93) occurred when the smoothing scale was set at 38, 6 and 9 km for reference levels of 1000, 2000 and 3000 db, respectively. The annual mean transport was estimated as 9.46 Sv in the 3000 db reference case. The Oyashio transport time series was derived from the T/P SSHA data, and the transports are smaller than that estimated from the Sverdrup balance in 1994–1996 and larger than that in 1997–2000. This difference is consistent with baroclinic response to wind stress field. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Analysis of freak wave measurements in the Sea of Japan   总被引：3，自引：0，他引：3  

Nobuhito Mori  Paul C. Liu  Takashi Yasuda 《Ocean Engineering》2002,29(11):1399-1414

This paper presents an analysis of a set of available freak wave measurements gathered from several periods of continuous wave recordings made in the Sea of Japan during 1986–1990 by the Ship Research Institute of Japan. The analysis provides an ideal opportunity to catch a glimpse of the statistics of freak waves in the ocean. The results show that a well-defined freak wave may occur in the developed wind–wave condition: S(f)∝f⁻⁴, with single-peak directional spectra. The crest and trough amplitude distributions of the observed sea waves including freak waves are different from the Rayleigh distribution, although the wave height distribution tends to agree with the Rayleigh distribution. Freak waves can be readily identified from the wavelet spectrum where a strong energy density occurs in the spectrum, and is instantly surged and seemingly carried over to the high-frequency components at the instant the freak wave occurs.  相似文献   

Dynamics of the Kuroshio large meander     

Ichiro Yasuda  Jong -Hwan Yoon  Nobuo Suginohara 《Journal of Oceanography》1985,41(4):259-273

The bimodality of the Kuroshio path is studied numerically with a barotropic inflow-outflow model. The dynamics that determines the path depends on the Rossby number,Ro (proportional to inlet velocity) and the Reynolds number (representing effects of viscosity). At lowRo (<Ro ₁) only a meander path occurs, while at highRo(Ro ₂) only a straight path is developed. Between these critical values (Ro ₁RoRo₂) either of the two paths can occur (multiple states), and the choice of path is determined by its history. Increase (decrease) inRo acrossRo ₂ (Ro ₁) leads to catastrophic transition from one path to the other. In the intermediate range (Ro ₁RoRo₂), the straight path is conditionally unstable to finite amplitude disturbances, and abrupt changes to the meander path take place. Absolute vorticity is almost conserved along the meander path, while along the straight path it is dissipated in large amount near the coast. At low Re, the flow tends to a viscous flow, and steady states are obtained. At highRe, time variations with different periods for the meander and straight paths become dominant. Intermittent transitions from one state to the other without any changes of external parameters are found at intermediateRo and at highRe.  相似文献