Wind-Tunnel Measurements Of Restitution Coefficients And Ejection Number Of Snow Particles In Drifting Snow: Determination Of Splash Functions

Wind-tunnel experiments of drifting snow were carried out andsplash functions were formulated to describe probability distributions of vertical restitution coefficient, horizontal restitution coefficient and ejection number when a natural snow particle collided at a natural snow surface. The following results were obtained:(1) The vertical restitution coefficient was usually larger than unity and decreased sharply with impact angle. At smaller impact angles around 5 degrees the vertical restitution coefficient exceeded a magnitude of ten.(2) The horizontal restitution coefficient, ranging from -1 to 1.5, decreased with impact velocity, but was not clearly dependent on impact angle.(3) The ejection number amounted to five per impact and increasedwith impact velocity.(4) Three splash functions to express the probability distributions of the vertical restitution coefficient, horizontal restitution coefficient and ejection number were formulated, which will be used in future computer simulations of the snow drifting process.     

Late Holocene Asian monsoon variations recorded in Lake Rara sediment,western Nepal

The Himalayas are a key location for understanding centennial‐ to millennial‐scale variations in the Asian monsoon, yet few studies of the late Holocene have been conducted in this sensitive area. Direct evidence for shifts in monsoonal wind strength is often limited to marine proxy records, while terrestrial reconstructions (e.g. lake levels and spleothems) focus on precipitation. Here, we present the first evidence of terrestrial summer monsoon wind strength changes from Lake Rara, western Nepal, based on Mn/Ti ratios, a proxy for lake stratification. These data indicate a link between the Arabian Sea and the Himalayas, suggesting that centennial‐ to millennial‐scale changes in wind strength occurred synchronously. Distinct similarity is also observed between Lake Rara and the southern part of China, which may support previous suggestions that the southern part of China is influenced by Indian summer monsoon. Copyright © 2012 John Wiley & Sons, Ltd.     

Establishment of numerical beach-litter hindcast/forecast models: an application to Goto Islands, Japan

This study attempts to establish a system for hindcasting/forecasting the quantity of litter reaching a beach using an ocean circulation model, a two-way particle tracking model (PTM) to find litter sources, and an inverse method to compute litter outflows at each source. Twelve actual beach survey results, and satellite and forecasted wind data were also used. The quantity of beach litter was hindcasted/forecasted using a forward in-time PTM with the surface currents computed in the ocean circulation model driven by satellite-derived/forecasted wind data. Outflows obtained using the inverse method was given for each source in the model. The time series of the hindcasted/forecasted quantity of beach litter were found consistent with the quantity of beach litter determined from sequential webcam images of the actual beach. The accuracy of the model, however, is reduced drastically by intense winds such as typhoons which disturb drifting litter motion.     

Oceanographic variations over the last 150,000 yr in the Japan Sea and synchronous Holocene with the Northern Hemisphere

The paleo-hydrography in the Japan Sea called a “mini-Ocean” was reconstructed based on the high-resolution analysis of diatom assemblages over the period of 150,000 yr. The decrease of diatom fertilization in the Japan Sea, when it was isolated from surrounding seas due to the drop of sea-level during the glacial to stadial phase, resulted in dissolution and/or extremely low diatom production in the northern cores in the subarctic water-masses. The annual Td′-derived paleo-SSTs (°C) were controlled by the fluctuations of 2-kyr and 4-kyr periods at intervals of 20 kyr and 40 kyr over the last 160 kyr BP, respectively. A 23-kyr cycle is recognized during the periods from 140 ka to 100 ka, according to the Wavelet analysis. After temperature and sea-level increased both at 133–128 ka, 60–53 ka and 15–10 ka, oceanic warm-water diatom species predominated at 127–119 ka and after 9 cal ka in the interstadial phase. At 21.3–16.9 ka and 12.9–9.8 ka, sea-level and salinity increased as the transgression developed. At 10.0–7.0 ka, the oceanic association shifted from cold-water species in the stadial period to warm-water ones in the interstadial phase. The fluctuations of Td′ derived-SSTs (°C) on century to millennial time-scales during the Holocene are well correlated with abrupt climatic events that different paleoclimatic proxies record in many regions of the Northern Hemisphere.     

Temporal variability of tsunami arrival detection distance revealed by virtual tsunami observation experiments using numerical simulation and 1-month HF radar observation

The combination of a high-frequency ocean surface radar and a tsunami detection method should be assessed as the onshore-offshore distribution of tsunami detection probability, because the probability will vary in accordance with the signal-to-noise ratio (SNR) and the tsunami magnitude in addition to the radar system specifications. Here, we statistically examine the tsunami detection distance based on virtual tsunami observation experiments by using signals received by a high-frequency radar in February 2014 installed on the southern coast of Japan and numerically simulated velocities induced by a Nankai Trough earthquake. In the experiments, the Doppler frequencies associated with the simulated velocities were superimposed on the receiving signals of the radar, and the radial velocities were calculated from the synthesized signals by the fast Fourier transform. Tsunami arrival was then detected based on the temporal change in the cross-correlation of the velocities, before and after tsunami arrival, between two points 3 km apart along a radar beam. We found that the possibility of tsunami detection primarily depends on the kinetic energy ratio between tsunami current and background current velocities. The monthly average detection probability is over 90% when the energy ratio exceeds 5 (offshore distance: 9 km ≤ L ≤ 36 km) and reduces to 50% when the energy ratio is approximately 1 (L = 42 km) over the shelf slope. The ratio varied with the background current physics and SNR, which was mainly affected by ocean surface wave heights and ionospheric electron density.     

Modeling the interannual variability and trends in gross and net primary productivity of tropical forests from 1982 to 1999

The role of tropical ecosystems in global carbon cycling is uncertain, at least partially due to an incomplete understanding of climatic forcings of carbon fluxes. To reduce this uncertainty, we simulated and analyzed 1982–1999 Amazonian, African, and Asian carbon fluxes using the Biome-BGC prognostic carbon cycle model driven by National Centers for Environmental Prediction reanalysis daily climate data. We first characterized the individual contribution of temperature, precipitation, radiation, and vapor pressure deficit to interannual variations in carbon fluxes and then calculated trends in gross primary productivity (GPP) and net primary productivity (NPP). In tropical ecosystems, variations in solar radiation and, to a lesser extent, temperature and precipitation, explained most interannual variation in GPP. On the other hand, temperature followed by solar radiation primarily determined variation in NPP. Tropical GPP gradually increased in response to increasing atmospheric CO₂. Confirming earlier studies, changes in solar radiation played a dominant role in CO₂ uptake over the Amazon relative to other tropical regions. Model results showed negligible impacts from variations and trends in precipitation or vapor pressure deficits on CO₂ uptake.     

Cyclic shear behaviour of steel box girders: experiment and analysis

An experimental investigation of the cyclic shear behaviour of steel box girders was conducted on one‐quarter scale models, comprising of two specimens with longitudinally unstiffened webs and one specimen with longitudinally stiffened webs. All the specimens exhibited ductile behaviour. The tests evidenced significant increases in the shear strength and energy dissipation capacity regarding the use of thicker webs and the provision of longitudinal web stiffeners. The web stiffeners also enhanced the stable hysteresis behaviour without substantial degradation in the energy dissipation due to pinching. The test results are compared with the shear behaviour simulated by inelastic large deformation analysis incorporated with a sophisticated constitutive model. The hysteresis behaviour, peak cyclic shear stresses, energy dissipation, and deformation shapes of the three specimens are satisfactorily predicted by the analysis. It is verified that the presented analytical method can be used precisely for further investigations of box girders in shear. Copyright © 2002 John Wiley & Sons, Ltd.     

Active right-lateral strike-slip fault zone along the southern margin of the Japan Sea

We describe an active right-lateral strike-slip fault zone along the southern margin of the Japan Sea, named the Southern Japan Sea Fault Zone (SJSFZ). Onshore segments of the fault zone are delineated on the basis of aerial photograph interpretations and field observations of tectonic geomorphic features, whereas the offshore parts are interpreted from single-/multichannel seismic data combined with borehole information. In an effort to evaluate late Quaternary activity along the fault zone, four active segments separated by uplifting structures are identified in this study. The east–northeast-trending SJSFZ constitutes paired arc-parallel strike-slip faults together with the Median Tectonic Line (MTL), both of which have been activated by oblique subduction of the Philippine Sea plate during the Quaternary. They act as the boundaries of three neotectonic stress domains around the eastern margin of the Eurasian plate: the near-trench Outer zone and NW–SE compressive Inner zone of southwest Japan arc, and the southern Japan Sea deformed under E–W compression from south to north.     

Growth of Emerald Crystals by Evaporation of Na2O—MoO3 Flux

Well-formed crystals of emerald, Be3AI2Si6O18:Cr, were easily grown from an Na2O-MoO3 flux by an isothermal technique. The crystal growth was conducted by heating a mixture of solute and flux at 1 100 ℃ for 24 h. The evaporation loss of flux depended on the amount of Na2O added to MoO3. Emerald crystals of lengths up to 2.1 mm and widths of 1. 4 mm were grown. The crystal sizes were dependent on the evaporation loss of the flux. The obtained crystals were transparent and exhibited the typical emerald-green color. The form of the emerald crystals was a twelve-sided prism bounded by well-developed faces. The aspect ratios were in the region of 1. 4 to 2. 3. The density was (2. 64±0.02) g/cm3. The IR absorption bands were in good agreement with the literature data.     

Long-term changes in distribution and chemistry of middle Miocene to Quaternary volcanism in the Chokai-Kurikoma area across the Northeast Japan Arc

Abstract To understand the characteristics of long‐term spatial and temporal variation in volcanism within a volcanic arc undergoing constant subduction since the cessation of back‐arc opening, a detailed investigation of middle Miocene to Quaternary volcanism was carried out within the Chokai‐Kurikoma area of the Northeast Japan Arc. This study involved a survey of available literature, with new K–Ar and fission track dating, and chemical analyses. Since 14 Ma, volcanism has occurred within the Chokai‐Kurikoma area in specific areas with a ‘branch‐like’ pattern, showing an east–west trend. This is in marked contrast to the widespread distribution of volcanism with a north–south trend in the 20–14 Ma period. The east–west‐ trending ‘branches’ are characterized by regular intervals (50–100 km) of magmatism along the arc. These branches since 14 Ma are remarkably discrepant to the general northwest–southeast or north‐northeast–south‐southwest direction of the crustal structures that have controlled Neogene to Quaternary tectonic movements in northeast Japan. In addition, evidence indicating clustering and focusing of volcanism into smaller regions since 14 Ma was verified. Comparison of the distribution and chemistry of volcanic rocks for three principal volcanic stages (11–8, 6–3 and 2–0 Ma) revealed that widely but sparsely distributed volcanic rocks had almost the same level of alkali and incompatible element concentrations throughout the area (with the exception of Zr) in the 11–8 Ma stage. However, through the 6–3 Ma stage to the 2–0 Ma stage, the concentration level in the back‐arc cluster increased, while that in the volcanic front cluster remained almost constant. Therefore, the degree of partial melting has decreased, most likely with a simultaneous increase in the depth of magma segregation within the back‐arc zone, whereas within the volcanic front zone, the conditions of magma generation have changed little over the three stages. In conclusion, the evolution of the thermal structure within the mantle wedge across the arc since 14 Ma has reduced the extent of ascending mantle diapirs into smaller fields. This has resulted in the tendency for the distribution of volcanism to become localized and concentrated into more specific areas in the form of clusters from the late Miocene to Quaternary.