Strengthening of the Walker circulation under globalwarming in an aqua-planet general circulation model simulation

Most climate models project a weakening of the Walker circulation under global warming scenarios. It is argued, based on a global averaged moisture budget, that this weakening can be attributed to a slower rate of rainfall increase compared to that of moisture increase, which leads to a decrease in ascending motion. Through an idealized aqua-planet simulation in which a zonal wavenumber-1 SST distribution is prescribed along the equator, we find that the Walker circulation is strengthened under a uniform 2-K SST warming, even though the global mean rainfall–moisture relationship remains the same. Further diagnosis shows that the ascending branch of the Walker cell is enhanced in the upper troposphere but weakened in the lower troposphere. As a result, a "double-cell" circulation change pattern with a clockwise(anti-clockwise) circulation anomaly in the upper(lower) troposphere forms, and the upper tropospheric circulation change dominates. The mechanism for the formation of the "double cell" circulation pattern is attributed to a larger(smaller) rate of increase of diabatic heating than static stability in the upper(lower) troposphere. The result indicates that the future change of the Walker circulation cannot simply be interpreted based on a global mean moisture budget argument.     

Biotic response of benthic foraminifera in Aso-kai lagoon,central Japan,to changes in terrestrial climate and ocean conditions (~AD 700–1600)

We investigated responses of shallow-water benthic foraminifera to changes in climate and ocean conditions, using sediment core ASC2 from Aso-kai lagoon, central Japan. Six AMS ¹⁴C dates reveal that the studied interval corresponds to sediments deposited from ~AD 700 to 1600. Sulfur content of the bulk sediment and multi-dimensional scaling (MDS) axis 1 of fossil benthic foraminifera indicate that the composition of the benthic foraminifera community was closely related to dissolved oxygen (DO) concentration in the hypolimnion. The sulfur content and MDS axis 1 also revealed two shifts over the 900-year interval. In the first phase (~AD 700–1250), the Shannon–Wiener Index (H′), E (S₂₀₀), evenness and rank abundance curve (RAC) kurtosis indicate a gradual deterioration in structure of the benthic foraminifera community. In that period, there are statistically significant correlations between the faunal composition (MDS axis 1) and faunal structure [Shannon–Wiener (H′), E (S₂₀₀), evenness and RAC kurtosis]. In the second phase (~AD 1250–1600), however, faunal composition and structure show no marked correspondence. Instead, abundance of benthic foraminifera fluctuated on a scale of ~200 years. Thus, a shift in the biotic response of benthic foraminifera in Aso-kai lagoon occurred in ca. AD 1250. Gradual deterioration of benthic foraminifera, with taxonomic losses, is consistent with declining DO in the first phase, possibly associated with the increasing influence of the Tsushima Warm Current. The possibility that closure of Aso-kai lagoon and development of the sand bar affected benthic foraminifera cannot, however, be ruled out. No corresponding response was observed in the second phase, during which there was no distinct taxonomic loss. Large variations in abundance, however, were a consequence of strength of the East Asian summer and winter monsoons. The shift in the biotic response of benthic foraminifera in Aso-kai lagoon during the period AD 700–1600 was apparently a result of changes in climate and ocean conditions on the East Asian continental margin.     

Mechanism of currents through the straits of the Japan Sea: Mean state and seasonal variation

The mechanism governing the mean state and the seasonal variation of the transports through the straits of the Japan Sea is studied using a newly presented, simple analytical model and a basin scale general circulation model (GCM). The GCM reproduces the transports through the straits of the Japan Sea realistically owing to its fine horizontal resolution of about 20 km and realistic topography. A series of experiments conducted by changing surface forcing shows that the annual mean wind-driven circulation in the North Pacific Ocean is most responsible for the formation of the mean transports. It is also found that the seasonal variation of the alongshore component of monsoonal wind stress over the North Pacific basin, especially that over the Okhotsk Sea, is responsible for the seasonal variation of the transports. The simple analytical model can explain these simulated features very well. The physical concept of this model is based on the formation of the around-island circulation through the adjustment of coastally trapped waves and Rossby waves and geostrophic control at the narrow straits. It solves the sea surface heights (SSHs) at the edge of each strait and the transport through it. The value of the line integral of the SSH along the island is determined by the baroclinic Rossby waves approaching the island from the east and the alongshore wind stress around the island. The basin scale seasonal variation of SSH along the coast induced by the variation of the alongshore monsoonal wind stress can also be incorporated into this model by giving the SSH anomaly at the northeastern point of the Soya Strait. Thus, it is suggested that both the mean state and the seasonal variation are caused mainly by wind stress forcing. Minor modification by the seasonal heat flux forcing brings the amplitude and the phase of the seasonal variation closer to the observed values.     

High-temperature Raman spectroscopy and quasi-harmonic lattice dynamic simulation of diopside

We investigated the lattice vibrational properties and lattice dynamical behaviour of diopside by combining laser micro-Raman spectroscopic measurements with quasi-harmonic lattice dynamic simulation using a transferable interatomic potential. We obtained polarized Raman spectra from a Fe-poor natural diopside and the temperature dependencies of the Raman modes to 1125?K from high-temperature Raman spectra of a Fe-poor and a Fe-rich natural diopside. The various modes display different temperature dependencies: from ?0.021?cm^?1/K to ?0.004?cm^?1/K. The temperature shift of low frequency modes is generally higher. A comparison of experimentally determined frequencies and symmetries of vibrational modes of the optical type (Raman and infrared) obtained in this and earlier studies with those calculated by us suggests that a consistent characterization of the vibrational properties was achieved. The good agreement between the experimental and simulated data on the temperature-dpendencies of the Raman modes (within 5%), crystal structure (2%), bulk modulus (5%), volume thermal expansivity (6%), and constant volume heat capacity (0.2%) testifies to the applicability of the transferable interatomic potential and the lattice dynamic model to predicting the vibrational, physical, and thermodynamic properties. The simulated properties from the lattice dynamic calculations are very similar to those obtained by molecular dynamic calculations with the same potential model.     

Statistical distribution of building lot frontage: application for Tokyo downtown districts

The frontage of a building lot is the determinant factor of the residential environment. The statistical distribution of building lot frontages shows how the perimeters of urban blocks are shared by building lots for a given density of buildings and roads. For practitioners in urban planning, this is indispensable to identify potential districts which comprise a high percentage of building lots with narrow frontage after subdivision and to reconsider the appropriate criteria for the density of buildings and roads as residential environment indices. In the literature, however, the statistical distribution of building lot frontages and the density of buildings and roads has not been fully researched. In this paper, based on the empirical study in the downtown districts of Tokyo, it is found that (1) a log-normal distribution fits the observed distribution of building lot frontages better than a gamma distribution, which is the model of the size distribution of Poisson Voronoi cells on closed curves; (2) the statistical distribution of building lot frontages statistically follows a log-normal distribution, whose parameters are the gross building density, road density, average road width, the coefficient of variation of building lot frontage, and the ratio of the number of building lot frontages to the number of buildings; and (3) the values of the coefficient of variation of building lot frontages, and that of the ratio of the number of building lot frontages to that of buildings are approximately equal to 0.60 and 1.19, respectively.     

Fractional-order derivative and time-dependent viscoelastic behaviour of rocks and minerals

A general constitutive equation for viscoelastic behaviour of rocks and minerals with fractional-order derivative is investigated. This constitutive law is derived based on differential geometry and thermodynamics of rheology, and the fractional order of derivative represents the degree of time delay. Analyzing some laboratory experimental data of high temperature deformation of rocks and minerals such as halite, marble and orthopyroxene, we propose how to determine the orders of fractional derivative for viscoelastic behaviours of rocks and minerals. The order is related to the exponents for the temporal scaling in the relaxation modulus and the stress power-law of strain rate, i.e., the non-Newtonian flow law, and considered as an indicator representing the macroscopic behaviour and microscopic dynamics of rocks.     

Seasonal changes in camera-based indices from an open canopy black spruce forest in Alaska,and comparison with indices from a closed canopy evergreen coniferous forest in Japan

Evaluation of the carbon, water, and energy balances in evergreen coniferous forests requires accurate in situ and satellite data regarding their spatio-temporal dynamics. Daily digital camera images can be used to determine the relationships among phenology, gross primary productivity (GPP), and meteorological parameters, and to ground-truth satellite observations. In this study, we examine the relationship between seasonal variations in camera-based canopy surface indices and eddy-covariance-based GPP derived from field studies in an Alaskan open canopy black spruce forest and in a Japanese closed canopy cedar forest. The ratio of the green digital number to the total digital number, hue, and GPP showed a bell-shaped seasonal profile at both sites. Canopy surface images for the black spruce forest and cedar forest mainly detected seasonal changes in vegetation on the floor of the forest and in the tree canopy, respectively. In contrast, the seasonal cycles of the ratios of the red and blue digital numbers to the total digital numbers differed between the two sites, possibly due to differences in forest structure and leaf color. These results suggest that forest structural characteristics, such as canopy openness and seasonal forest-floor changes, should be considered during continuous observations of phenology in evergreen coniferous forests.     

Experimental and Numerical Investigations of Ground Deformation Using Chemical Grouting for Pipeline Foundation

Based on experimental and numerical investigations, the present paper focuses on under ground scope (UGS) chemical grouting method that can actually improve the pipeline surrounding foundation to solve pipeline saggy damage. According to the experimental results, a solution-type injection material could make lager soil deformation, using less total slurry amount than suspension-type injection material. Therefore, a suspension-type injection material with shorter gel time is more suitable for the UGS method, making it more effective to reinforce the pipeline foundation and restore pipelines. The results of some patterns of injection tests revealed relationship between the behavior of the grouting material and the deformation of the soil. It is found that the material can be injected into a foundation by fracture grouting if the permeation coefficient is lower than 1.00 × 10⁻³ mm/s. The situation was analyzed by using 2-D finite element method analysis software Phase2, and the analysis result proposes that the real data and simulation data are nearly the same in impermeable soil. Furthermore, even if the construction object is permeable soil, it can also be become impermeable soil by two phases grouting: soil improvement grouting and restoration grouting.     

Subhorizontal tectonic framework of the Horoman peridotite complex and enveloping crustal rocks,south‐central Hokkaido,Japan

Geological observations in the Horoman area, south‐central Hokkaido, show that the Horoman peridotite complex of the Hidaka metamorphic belt is a tectonic slice about 1200 m thick. The peridotite slab is intercalated into a gently east‐dipping structure. The underlying unit is a Cretaceous–Paleogene accretionary complex. Riedel shear planes in the sedimentary layers of the accretionary complex near the structural bottom of the peridotite slab indicate top‐to‐the‐west (thrust) displacement. The overlying unit is composed of felsic–pelitic gneisses and mafic–felsic intrusive rocks (the Hidaka metamorphic rocks). The boundary surface between the peridotite complex and metamorphic rocks forms a domal structure. Microstructures of sheared metamorphic rocks near the structural top of the peridotite slab indicate top‐to‐the‐east (normal) displacement. The results combined with previous studies suggest that the Horoman peridotite complex was emplaced onto the Asian margin (Northeast Japan) during the collision between the Asian margin and the Hidaka crustal block.