DISTRIBUTION OF AEROSOL EXTINCTION IN THE LOWER TROPOSPHERE BY MICRO-PULSE LIDAR OBSERVATION

The profiles of aerosol extinction coefficients are investigated by micro-pulse lidar(MPL)combined with the meteorological data in the lower troposphere at Meteorological ResearchInstitute(MRI).Japan.Larger extinction values of aerosol are demonstrated in the nocturnalstable air layer with larger Richardson number,and light wind velocities are favorable for aerosolconcentrating in the planetary boundary layer(PBL).But aerosol extinction coefficients showlarger values over the altitudes of 2.0 to 5.0km where correspond to higher relative humidity(RH).The tops of PBL identified by the aerosol extinction profiles almost agree with ones byradiosonde data.The diurnal variations of aerosol extinction profiles are clearly displayed,intensive aerosol layers usually are formed over the period of mid-morning to 1400 Loeal Time(LT).then elapse in the cloudless late afternoon and nighttime.Thermal eonvection or turbulenttransport from the surfaee probably dominates these temporal and spatial changes of aerosoldistribution.     

Implication of the temporal sulphur isotopic variation during the 2000 eruption of Miyakejima Volcano, Japan

Abstract   The variation of sulphur isotopic composition during the 2000 eruption of the Miyakejima Volcano was examined in order to monitor the temporal change of the volcanic activity. The δ³⁴S values of water-soluble sulphate leached from volcanic ash effused during intermittent eruptions from July to September 2005 range from +5 to +11‰ with a fluctuation of ca 3‰ within a single eruption. The δ³⁴S value of sulphuric acid mist collected with 'Cu-metal trap' placed on the flank of the volcano from December 2000 to January 2001 is +6.2‰. These sulphur isotopic compositions of sulphate, which were isotopically equilibrated in the subvolcanic hydrothermal system, indicate that the temperature of the hydrothermal system beneath the caldera increased after the period of intermittent phreatic and phreatomagmatic eruptions. Then, the δ³⁴S value of sulphuric acid trapped from January to March 2001 was +9.0‰ and the δ³⁴S value of water-soluble sulphate on volcanic ash emitted with minor eruption in May 2001 was +11.0‰, suggesting a decrease in temperature of the subvolcanic hydrothermal system.     

Molecular and isotopic composition of hydrate-bound and dissolved gases in the southern basin of Lake Baikal, based on an improved headspace gas method

Assessments of the molecular and isotopic composition of hydrate-bound and dissolved gases in pore water were conducted during the multi-phase gas hydrate project (MHP-09) cruise VER09-03 to the southern basin of Lake Baikal in September 2009. To avoid changes in gas composition during core sampling and transport, various headspace methods were investigated aimed at preserving the dissolved gases in pore water. When distilled water was added to the sediment samples, the concentrations of carbon dioxide and oxygen decreased because of dissolution into the water and/or microbial consumption. When the headspace was not flushed with inert gases, trace levels of hydrogen and ethylene were detected. The findings suggest that best preparation is achieved by flushing the headspace with helium, and adding a saturated aqueous solution of sodium chloride. This improved headspace method served to examine the molecular and isotopic compositions of gas samples retrieved at several new sites in the southern basin. Methane was the major component, and the proportion of ethane ranged widely from 0.0009 to 1.67?mol% of the total hydrocarbon gases. The proportions of propane and higher hydrocarbons were small or less than their detection limits. The carbon isotope signatures suggest that microbial-sourced methane and ethane were dominant in the Peschanka study area, whereas ethane was of thermogenic origin at all other study sites in the southern basin of Lake Baikal.     

A Massive Coccolithophorid Bloom Observed in Mikawa Bay, Japan

In April 1996, a massive algal bloom of the coccolithophorid Gephyrocapsa oceanica developed in both Chita Bay and Atsumi Bay which comprise the bay known as Mikawa Bay of Japan. It was the first record of such a bloom in this area. In Chita Bay, the bloom persisted until the middle of May, however in Atsumi Bay, it remained until early June. From the analysis of salinity, water temperature, and current velocity and direction data, it is considered that the following mechanism accounts for the occurrence and maintenance of the bloom: Before the bloom, the standing crop of phytoplankton was poor, resulting in relatively rich nutrients throughout the bay. Thereafter, with the influx of oceanic water into Mikawa Bay, high salinity occurred firstly in Chita Bay. Under these hydrographic conditions, the bloom occurred first in Chita Bay, and extended throughout the bay with the clockwise circulation of water into Atsumi Bay. In Chita Bay, the bloom was influenced by rainfall and G. oceanica flowed out from this area. Whereas, in Atsumi Bay, the bloom persisted for longer due to the clockwise circulation and another influx of oceanic water.     

Quartz microtextures of the Sambagawa schists and their implications in convergent margin processes

Abstract Quartz c-axis fabrics of the Sambagawa schists produced along a late Mesozoic convergent plate margin were analysed so that their tectono-metamorphic history could be clarified. It has been noted by many authors that quartz fabrics produced by earlier phase deformation are easily modified by strain increment during later phase deformation. This paper attempts to elucidate the high-temperature phases of prograde metamorphism (Sim-Bim phase) and of retrograde metamorphism (Sb₁ phase and Sb₂₋₁ phase) from quartz grains included in garnet and plagioclase porphyroblasts. Quartz c-axis fabrics for all these phases are explained in terms of a type I crossed girdle, without (only rarely with) higher concentration in the principal axis of strain Y (X>Y>Z), that must have been produced by the activity of a dominant slip system such as rhomb and basal. As a result, the plastic deformation of quartz, which was responsible for the formation of the type I crossed girdle, occurred even under temperatures greater than 500°C and pressures a little greater than 10–11 kb, which correspond to the physical condition of the Sim-Bim phase. It has been assumed that a high strain rate (and/or low H₂O content) caused rhomb and basal to be active as dominant slip systems in the subduction zone related to the formation of the Sambagawa schists even under high temperatures (> 500°C).     

Star formation histories of local group dwarf galaxies

We present the study of the star formation histories (SFHs) of a sample of Local Group dwarf galaxies (LGDGs), via the analysis and modelling, with the means of an evolutionary stellar population synthesis, of their colour-magnitude (CM) diagrams. It appears that important parameters to describe the SFHs are star formation rate (SFR) and duration of star formation. We find a possible correlation between the mass and the SFRs. The correlation might be the origin of the observed luminosity-metallicity relation in the LGDGs. A well-defined correlation between the durations of star formation and the distance from M31 or the Galaxy indicates that the current early-type dwarf galaxies should have been transformed from late-type by strong tidal force of the massive galaxies. This revised version was published online in August 2006 with corrections to the Cover Date.     

Onset of coastal upwelling in a two-layer ocean by wind stress with longshore variation

On the assumption that motions of the barotropic mode are horizontally nondivergent, action of the wind stress with longshore variation on a two-layer ocean adjacent to the meridional east coast is studied. Only the equatorward wind stress is considered. Along the east coast, upwelling is induced by the direct effect of the coast and is confined in a narrow strip with the width of the order of the internal radius of deformation. The upwelling propagates poleward with the internal gravity wave speed. Coastal upwelling induced by the wind stress with longshore variation may be interpreted as the generation and propagation of internal Kelvin waves. Associated with the coastal upwelling, the equatorward flow in the upper layer and the poleward flow in the lower layer are formed as an internal mode of motions. When the bottom topography with the continental shelf and slope is taken into account, occurrence of the poleward undercurrent is delayed by a few days because of the generation of continental shelf waves. And, after the forcing is stopped, the shelf waves propagate poleward away from the upwelling region and the poleward undercurrent fully develops. At the margin of the continental shelf, another upwelling region is induced and propagates poleward.     

Coastal polynyas off East Queen Maud Land observed from NOAA AVHRR data

Coastal polynyas off East Queen Maud Land in Antarctica are examined using NOAA AVHRR infrared data. From image analyses, two locations of coastal polynyas in this region are identified; one in Breid Bay and the other along the shelf break. The areal coverage of the Breid Bay polynya is significantly related to the strength of katabatic winds, which maintain their strength over the coastal sea due to land topography favoring for their confluence, thereby being capable of removing newly formed ice. Land fast ice in the eastern part of the bay also plays an additional role in the formation mechanism. It is also found that the areal coverage of coastal polynyas in this region fluctuate coherently. Moreover, these fluctuations correspond to the synoptic index, which measures the strength of the offshore wind, with their peaks closely associated with the areal peaks. These facts strongly suggest the influence of synoptic scale weather on the formation and maintenance of polynyas in this region.     

Upwelling front and two-cell circulation in a two-dimensional model

The intensification of upwelling front and two-cell circulation is studied numerically in a two dimensional level model. Upwelling front is set initially with longshore geostrophic flow. The uniform wind stress forces the ocean which has an infinite north-south coast line. Two-cell circulation, downwelling just inshore-side of the front and upwelling offshore-side, is induced, and the front is intensified. It is found that the intensification is occurred in the inshore-side of the front, and the intensification is basically due to the deviation from the thermal-wind balance, as is shown bySuginohara (1977). It is found that the inshore-side cell intrudes under the pycnocline. It seems to reproduce the observed two-cell circulation.     

Improved version of BTOPMC model and its application in event-based hydrologic simulations

In this paper, a grid-based distributed hydrological model BTOPMC (Block-wise use of TOPMODEL) is introduced, which was developed from the original TOPMODEL. In order to broaden the model’s application to arid regions, improvement methodology is also implemented. The canopy interception and soil infiltration processes were incorporated into the original BTOPMC to model event-based runoff simulation in large arid regions. One de-signed infiltration model with application of time compression approximation method is emphasized and validated for improving model’s performance for event hydrological simulations with a case study of Lushi River basin.