Distribution of the subsurface chlorophyll maximum and its nutrient-light environment in and around the Euroshio off Japan

Continuous distribution of the subsurface chlorophyll maximum (SCM) was confirmed in the Kuroshio and neighbouring areas in observations at 15 to 40 km intervals. Chlorophyll amounts occurring in and immediately around the SCM constituted 60 to 80% of the total chlorophyll in the water column above the 1% light level. The SCM zone received 1 to 10% of the surface irradiance at its center and contained sufficient macronutrients to support approximately one doubling of the existing phytoplankton biomass at most stations. There were several stations where there were higher nutrient concentrations that would support more than one doubling of the existing biomass around the SCM zone, and this was interpreted as resulting from uplift of the SCM zone due to upwelling.     

Photosynthetic pigment system of picophytoplankton of cyanophytes isolated from subsurface water in the Kuroshio area

Photosynthetic pigment system of picophytoplankton of cyanophytes was examined with five strains isolated from the Kuroshio water at the depth of 70 m. Examination was made for the absorption spectra of intact cells of each strain. Analysis of pigment composition was also made withSynechococcus NIBB 1059 and 1071, which were isolated from surface waters of the Gulf Stream and Kuroshio area, respectively. Results indicated that (1) all strains contain phycoerythrin with a very high concentration, and (2) the phycoerythrin in these strains contains two chromophores, phycoerythrobilin and phycourobilin, and (3) a large abundance of phycoerythrin and phycourobilin in the phycoerythrin enablesSynechococcus picophytoplankton to absorb effectively the light in the blue-green region at the subsurface depth. These characteristics suggest that cyanophytes in the subsurface water can collectt the blue-green light and perform actively photosynthesis even at the bottom of euphotic layer.     

Forced convection accompanying wind waves

Wind-wave tunnel experiments reveal, by use of techniques of the flow visualization, that wind waves are accompanied by the wind drift surface current with large velocity shear and with horizontal variation of velocity relative to the wave profile. The surface current converges from the crest to a little leeward face of the crest, making a downward flow there, even though the wave is not breaking. Namely, wind waves are accompanied by forced convections relative to the crests of the waves. Since the location of the convergence and the downward flow travels on the water surface as the crest of the wave propagates, the motion as a whole is characterized by turbulent structure as well as by the nature of water-surface waves. In this meaning, the term of real wind waves is proposed in contrast with ordinary water waves. The study of real wind waves will be essential in future development of the study of wind waves.     

Geological relationship between Anyui Metamorphic Complex and Samarka terrane,Far East Russia

The Anyui Metamorphic Complex (AMC) of Cretaceous age is composed of metachert, schist, gneiss, migmatite and ultramafic rocks, and forms a dome structure within the northernmost part of the Jurassic accretionary complex of the Samarka terrane. The two adjacent geological units are bounded by a fault, but the gradual changes of grain size and crystallinity index of quartz in chert and metachert of the Samarka terrane and the AMC, together with the gradual lithological change, indicate that at least parts of the AMC are metamorphic equivalents of the Samarka rocks. Radiolarian fossils from siliceous mudstone of the Samarka terrane indicates Tithonian age (uppermost Jurassic), and hence, form a slightly later accretion. This signifies that the accretionary complex in the study area is one of the youngest tectonostratigraphic units of the Samarka terrane. The relationship between the Samarka terrane and AMC, as well as their ages and lithologies, are similar to those of the Tamba–Mino–Ashio terrane and Ryoke Metamorphic Complex in southwest Japan. In both areas the lower (younger) part of the Jurassic accretionary complexes were intruded and metamorphosed by Late Cretaceous granitic magma. Crustal development of the Pacific‐type orogen has been achieved by the cycle of: (i) accretion of oceanic materials and turbidites derived from the continent; and (ii) granitic intrusion by the next subduction and accretion events, accompanied by formation of high T/P metamorphic complexes.     

Wind Fields over Funka Bay and Their Effect on Water Circulation in the Bay

Horizontal wind fields over Funka Bay during cold air outbreaks were simulated using a 3-D meso-scale atmospheric model. The simulated wind fields over the bay have a positive curl in the north and a negative curl in the south. These wind fields were used to simulate the current in Funka Bay using a barotropic ocean model. The simulated current pattern was composed of two vortices—one with anti-clockwise vorticity in the north and the other with clockwise vorticity in the south—and was in the opposite direction to that simulated by the uniform wind fields. This is because the wind stress curl effect on the vorticity production in Funka Bay opposes and overwhelms the bathymetry torque effect during cold air outbreaks. These results show that the non-uniformity of the wind fields caused by the land topography around a shallow lake or bay cannot be neglected in simulating its currents.     

Altitudinal Distribution Of 20 Persistent Meteor Trains: Estimates Derived From Metro Campaign Archives

Observations of persistent meteor trains are limited because of the extreme rarity of the phenomenon. The altitudinal distribution of persistent trains has previously been investigated via limited instances of simultaneous observation from multiple sites, however, a statistical study of persistent trains has yet to be realized. The meteor train observation (METRO) campaign was established in Japan in 1998 to obtain images of persistent trains. From 1998 to 2002, the METRO campaign, involving Japanese amateur collaborators, captured more than 400 image sequences of persistent trains, resulting in 53 simultaneous multi-site observations. Several Japanese observers were involved in imaging persistent trains prior to the METRO campaign, producing 6 simultaneous observations over the period 1988–1997. In this paper, simultaneous multi-site observations of high spatial and temporal resolution are used to determine, via triangulation, the altitudinal distribution of persistent trains for 20 events. The altitudinal range of 2 Orionid trains was slightly higher than that of 18 Leonid trains. The Leonid train data reveal no clear dependence of upper and lower altitude on the brightness of the associated fireball. The upper altitude of the 18 observed Leonid trains were almost invariant with respect to local time (LT) of observation, however, a possible dependence of lower altitude on LT of observation was also found, indicating a near-constant penetrating path-length in the upper atmosphere for each train. The average upper altitude of persistent Leonid trains was 99.8 km, while the average central altitude was 93.0 km. These trends are probably determined by atmospheric conditions such as the abundance of O and O₃.     

Local time asymmetries of the SSC-associated hydromagnetic variations at the geosynchronous altitude

167 SSC events have been studied by using the data observed at the multiple-satellites at the geosynchronous altitude. The strong local time asymmetry of the SSC amplitude which was found by Kokubun (1983) has been confirmed. The pronounced local time asymmetry has also been found with the direction of the initial movement of Psc magnetic pulsations. Those local time effects are interpreted by the intensification of the magnetopause surface current during a SSC event, and by the distance between the geosynchronous satellite and the surface current. It has also been clarified that the SSC signal propagates with a speed of 400–700 km s^?1 across the field lines in the magnetosphere as suggested by Wilken et al. (1982).     

Simulating the carbon balance of a temperate larch forest under various meteorological conditions

Background  

Changes in the timing of phenological events may cause the annual carbon budget of deciduous forests to change. Therefore, one should take such events into account when evaluating the effects of global warming on deciduous forests. In this article, we report on the results of numerical experiments done with a model that includes a phenological module simulating the timing of bud burst and other phenological events and estimating maximum leaf area index.     

Mineral chemistry of MUSES‐C Regio inferred from analysis of dust particles collected from the first‐ and second‐touchdown sites on asteroid Itokawa

The mineralogy and mineral chemistry of Itokawa dust particles captured during the first and second touchdowns on the MUSES‐C Regio were characterized by synchrotron‐radiation X‐ray diffraction and field‐emission electron microprobe analysis. Olivine and low‐ and high‐Ca pyroxene, plagioclase, and merrillite compositions of the first‐touchdown particles are similar to those of the second‐touchdown particles. The two touchdown sites are separated by approximately 100 meters and therefore the similarity suggests that MUSES‐C Regio is covered with dust particles of uniform mineral chemistry of LL chondrites. Quantitative compositional properties of 48 dust particles, including both first‐ and second‐touchdown samples, indicate that dust particles of MUSES‐C Regio have experienced prolonged thermal metamorphism, but they are not fully equilibrated in terms of chemical composition. This suggests that MUSES‐C particles were heated in a single asteroid at different temperatures. During slow cooling from a peak temperature of approximately 800 °C, chemical compositions of plagioclase and K‐feldspar seem to have been modified: Ab and Or contents changed during cooling, but An did not. This compositional modification is reproduced by a numerical simulation that modeled the cooling process of a 50 km sized Itokawa parent asteroid. After cooling, some particles have been heavily impacted and heated, which resulted in heterogeneous distributions of Na and K within plagioclase crystals. Impact‐induced chemical modification of plagioclase was verified by a comparison to a shock vein in the Kilabo LL6 ordinary chondrite where Na‐K distributions of plagioclase have been disturbed.