TheKyucho in Uwajima Bay

The phenomenon of rapid increase in water temperature accompanied by a sudden, swift current (Kyucho) in Uwajima Bay is described on the basis of results of long term observations from July 1985 to September 1986. This phenomenon occurs somewhat periodically with an interval of about 15 days in summer, although it does not occur in winter. The increase in water temperature occasionally reaches about 5°C. This phenomenon results from the intrusion of a warm water mass into the bay. NOAA-9 satellite images show that the warm water mass originates from the Pacific Ocean south of the Bungo Channel.     

Graphitization of carbonaceous matter during metamorphism with references to carbonate and pelitic rocks of contact and regional metamorphisms,Japan

This study is an attempt to correlate the graphitization process of carbonaceous matter during metamorphism with metamorphic grade. Graphitization can be parameterized using crystal structure and chemical and isotopic compositions. The extent of graphitization could be characterized mainly by temperature, duration of metamorphism and rock composition. We compared the graphitization trends for two metamorphic terrains, a contact aureole of the Kasuga area and a regional metamorphic terrain of high-temperature/low pressure type of the Ryoke metamorphic terrain in Northern Kiso area, Central Japan, and for two different lithologies (carbonate and pelite), using X-ray diffractogram, DTA-TG analysis, and chemical and stable isotope analyses. During contact metamorphism, graphitization and carbon isotopic exchange reactions proceeded simultaneously in pelitic and carbonate rocks. The decreases in basal spacing d(002) of the carbonaceous matter in carbonate rocks is greatly accelerated at temperatures higher than about 400° C. Furthermore, carbon isotopic ratios of graphite in carbonate rocks also change to ¹³C-enriched values implying exchange with carbonates. The beginning of this enrichment of ¹³C in the carbonaceous matter coincides with an abrupt increase of the graphitization processes. Carbon isotopic shifting up to 5 in pelites could be observed as metamorphic temperature increased probably by about 400° C. Carbonaceous matter in pelitic rocks is sometimes a mixture of poorly crystallized organic matter and well-crystallized graphite detritus. DTA-TG analysis is an effective tool for the distinction of detrital graphitic material. Two sources for the original carbon isotopic composition of carbonaceous matter in pelites in the Kasuga contact aureole can be distinguished, about-28 and-24 regardless of the presence of detrital graphite, and were mainly controlled by depositional environment of the sediments. Graphitization in limestones and pelitic rocks in regional metamorphism proceeds further than in a contact aureole. In the low-temperature range, the differences in extent of graphitization between the two metamorphic regions is large. However, at temperatures higher than 600° C, the extent of graphitization in both regions is indistinguishable. The degree of graphitization is different in limestones and pelitic rocks from the Ryoke metamorphic terrain. We demonstrate that the graphitization involves a progressive re-construction process of the crystal structure. The sequence of the first appearance of crystal inter planar spacing correlates with the metamorphic grade and indicates the crystal growth of three-dimensional structured graphite.     

Evaluation of spatial correlation between nutrient exchange rates and benthic biota in a reef-flat ecosystem by GIS-assisted flow-tracking

A Geographic Information System (GIS)-aided flow-tracking technique was adopted to investigate nutrient exchange rates between specific benthic communities and overlying seawater in a fringing reef of Ishigaki Island, subtropical Northwestern Pacific. Net exchange rates of NO₃ ⁻, NO₂ ⁻, NH₄ ⁺, PO₄ ³⁻, Total-N and Total-P were estimated from concentration changes along the drogue trajectories, each of which was tracked by the Global Positioning System and plotted on a benthic map to determine the types of benthic habitat over which the drogue had passed. The observed nutrient exchange rates were compared between 5 typical benthic zones (branched-coral (B) and Heliopora communities (H), seaweed-reefrock zone (W), bare sand area (S), and seagrass meadow (G)). The dependence of nutrient exchange rates on nutrient concentrations, physical conditions and benthic characteristics was analyzed by multiple regression analysis with the aid of GIS. The spatial correlation between nutrient exchange rates and benthic characteristics was confirmed, especially for NO₃ ⁻ and PO₄ ³⁻, which were usually absorbed in hydrographically upstream zones B and W and regenerated in downstream zones H and G. NO₃ ⁻ uptake in zones B and W was concentration-dependent, and the uptake rate coefficient was estimated to be 0.58 and 0.67 m h⁻¹, respectively. Both nutrient uptake in zone W and regeneration in zone H were enhanced in summer. The net regeneration ratio of NO₃ ⁻/PO₄ ³⁻ in zone H in summer ranged 5.2 to 34 (mean, 17.4), which was somewhat higher than previously measured NO₃ ⁻/PO₄ ³⁻ for sediment pore waters around this zone (1.1–8.5). Nutrient exchanges in zone S were relatively small, indicating semi-closed nutrient cycling at the sediment-water interface of this zone. NH₄ ⁺ efflux from sediments was suggested in zone G. The data suggest that the spatial pattern of nutrient dynamics over the reef flat community was constrained by zonation of benthic biota, and that abiotic factors such as nutrient concentrations and flow rates, influenced nutrient exchange rates only in absorption-dominated communities such as zones B and W.     

Application of WetSpass model to estimate groundwater recharge variability in the Nile Delta aquifer

Long-term groundwater recharge from rainfall in the Nile Delta is needed as an input for integrated groundwater modelling in the Nile Delta aquifer for more accurate simulation. The main objective is to estimate the spatial and temporal variation of groundwater recharge from rainfall in the Nile Delta aquifer. Water and Energy Transfer between Soil, Plants and Atmosphere under quasi-Steady State (WetSpass) model parameters were identified for the Nile Delta based on the available meteorological data for the area collected in 1991 and 2000. The collected data were rainfall, temperature, wind speed and evapotranspiration. Geomorphological characteristics, such as soil type, topography, groundwater depth and slope, were also collected as input data for the WetSpass model. ENVI software was used to come up with land use classification based on available land cover images of the Nile Delta for 1972, 1984, 1990, 2000 and 2009. The WetSpass model was calibrated by comparing the simulated groundwater recharge with the calculated one by using the water balance equation model. The results indicated close agreement in groundwater recharge between the two model outputs with R ² of 0.99 and 0.94, while the root-mean-square errors (RMSEs) were 4.86 and 9.39 mm for 1991 and 2000, respectively. The WetSpass model was then applied in respect of 1970, 1980, 1990 and 2010 for the purpose of validation. The overall RMSE and R ² for the 6 years were 8.83 mm and 0.88, respectively. The results of the WetSpass calibrated model provide information to support integrated groundwater modelling. The results reveal that WetSpass works well in simulating the components of the hydrological balance in the Nile Delta.     

Iron nutritional status of the phytoplankton assemblage in the Okhotsk Sea during summer

To clarify the iron (Fe) nutritional status of the phytoplankton assemblage in the Okhotsk Sea, we conducted incubation experiments in summer 2006. Replicate surface seawater samples with the natural plankton community were incubated with three treatments: Fe enrichment; addition of the strong Fe chelator siderophore desferriferrioxime B (DFB) which strips Fe from the biologically accessible pool; and as a control, no addition. To prevent macronutrient limitation, we added surplus nutrients to all treatments. At all 4 stations in Sakhalin Bay near the mouth of the Amur River and around the east of Sakhalin Island, net specific growth rate showed no significant difference between the control and +Fe treatment, and was repressed in +DFB treatment both in large- and small-sized phytoplankton. These findings indicate that these waters contain sufficient bioavailable Fe and that the Amur River plume which is transported by the east Sakhalin current is a major source of the Fe. In the Bussol’ Strait, net specific growth rate in the control was significantly higher than +DFB treatment, suggesting a supply of bioavailable Fe through intense vertical mixing at this site. Iron enrichment treatment stimulated the net specific growth rate of large-sized phytoplankton, indicating that Fe still limits the growth for the large-sized phytoplankton assemblage, but not for small-sized phytoplankton, in this area. An index of Fe availability was defined to quantify the degree of ambient Fe availability in each station, and it revealed the spatial variability of ambient Fe availabilities among the sites.     

YOHKOH/WBS Recalibration and a Comprehensive Catalogue of Solar Flares Observed by YOHKOH SXT, HXT and WBS Instruments

The flare catalogue of the Yohkoh mission is compiled and linked to this article as an electronic supplement. For showing flare characteristics over wide energy range concisely, we provide the images of Hard X-ray Telescope (HXT) and the Soft X-ray Telescope (SXT), and the spectra of Hard X-ray Spectrometer (HXS) and Gamma-Ray Spectrometer (GRS) with the Wide Band Spectrometer (WBS) time profiles. The energy versus pulse height (PH) data channels in HXS and GRS are re-calibrated by using the data of the whole mission period. Secular gain changes are recognized in HXS, and the characteristics of power-law flare spectra simultaneously observed by HXT and HXS confirms the trend. The GRS gains are different for the flare observations during the previous maximum and for the current maximum. The total of 33 γ -ray events are observed, and for 12 of them γ-ray flare spectra are obtained. Electronic supplementary material to this article is available at and is accessible for authorized users.     

Quiescent Reconnection Rate Between Emerging Active Regions and Preexisting Field,with Associated Heating: NOAA AR 11112

When magnetic flux emerges from beneath the photosphere, it displaces the preexisting field in the corona, and a current sheet generally forms at the boundary between the old and new magnetic domains. Reconnection in the current sheet relaxes this highly stressed configuration to a lower energy state. This scenario is most familiar and most often studied in flares, where the flux transfer is rapid. We present here a study of steady, quiescent flux transfer occurring at a rate three orders of magnitude lower than that in a large flare. In particular, we quantify the reconnection rate and the related energy release that occurred as the new polarity emerged to form NOAA Active Region 11112 (SOL16 October 2010T00:00:00L205C117) within a region of preexisting flux. A bright, low-lying kernel of coronal loops above the emerging polarity, observed with the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory and the X-ray Telescope onboard Hinode, originally showed magnetic connectivity only between regions of newly emerged flux when overlaid on magnetograms from the Helioseismic and Magnetic Imager. Over the course of several days, this bright kernel advanced into the preexisting flux. The advancement of an easily visible boundary into the old flux regions allows measuring the rate of reconnection between old and new magnetic domains. We compare the reconnection rate with the inferred heating of the coronal plasma. To our knowledge, this is the first measurement of steady, quiescent heating related to reconnection. We determined that the newly emerged flux reconnects at a fairly steady rate of 0.38×10¹⁶ Mx?s^?1 over two days, while the radiated power varies between (2?–?8)×10²⁵ erg?s^?1 over the same time. We found that as much as 40 % of the total emerged flux at any given time may have reconnected. The total amounts of transferred flux (～?1×10²¹ Mx) and radiated energy (～?7.2×10³⁰ ergs) are comparable to that of a large M- or small X-class flare, but are stretched out over 45 hours.     

Production and bacterial decomposition of dissolved organic matter in a fringing coral reef

The concentrations of dissolved organic carbon and nitrogen (DOC and DON, respectively) were measured in Shiraho fringing reef (Japan), using a high-temperature catalytic-oxidation method. When the seawater on the reef flat (shallow lagoon) was isolated from the surrounding ocean due to the low tide, the concentrations of DOC and DON on the reef flat were 66–75 and 4.8–5.7 μmol l⁻¹, respectively. The DOC and DON concentrations were higher than those of the adjacent outer ocean (57–58 and 3.8 μmol l⁻¹, respectively), suggesting that the coral reef functioned as a net source of dissolved organic matter for the surrounding ocean. In order to investigate long-term bacterial decomposition of the reef-derived DOC (RF-DOC), the seawater samples collected on the reef flat and at the adjacent ocean were incubated in the dark for 1 year. Regression analysis using an exponential curve that considered two degradability pools (labile and refractory) fitted the mineralization of the RF-DOC very well (r ² > 0.89). According to the regression analysis, the DOC produced on the reef flat was composed of the labile fraction of 63–94% (average 77%) and the refractory fraction of 6–37% (average 23%). It was concluded that some of the DOC that was produced in the coral reef ecosystem was exported to the surrounding ocean if the reef flat had a water residence time less than several months. The exported organic matter may support microbial communities in the ocean as an energy source.     

Dynamical Features and Evolutional Characteristics of Brightening Coronal Loops

We present a detailed study of coronal loop brightenings observed in an active region on the solar limb. These brightening loops show expanding and shrinking motions in EUV coronal line images and also show downflow along the loops in Lα and Hα images. By means of time-slice analysis of the images, we found that both the expanding and shrinking motions of the loops are not real motions of plasma but apparent motions like post-flare loops, where the loops at the different height are successively heated and cooled. From a temperature analysis, the time delay between the brightenings of hot 195 Å and cool Lα loops is found to be nearly equal to the time-scale of the conduction cooling. We conclude that these loop brightenings are sources of so called Hα coronal rains.     

High pressure phase equilibria in the system CaTiO3-CaSiO3: stability of perovskite solid solutions

Phase relations in the system CaTiO₃-CaSiO₃ were experimentally examined at 5.3–14.7 GPa and 1200–1600 °C with a 6–8 type multianvil apparatus. As pressure increases, stability field of perovskite solid solution extends from CaTiO₃ to CaSiO₃, and the perovskite becomes stable for the entire composition range above about 12.3 GPa. The stability field of Ca(Ti_1?X, Si_X)₂O₅ (0.78<x≦1) titanite solid solution +Ca₂SiO₄ larnite exists in the CaSiO₃-rich composition range at 9.3–12.3 GPa and 1200 °C. Perovskite solid solutions containing CaSiO₃ component of 0 to 66 mol% could be quenched to 1 atm. The composition-molar volume relationship of perovskite solid solution showed that molar volume of perovskite solid solution linearly reduces from the value of CaTiO₃ to that of CaSiO₃.