Possible shrinking of the primary component of epsilon aurigae

Radial velocities of the primary star of Aur are presented for phases outside the eclipse between 1975 and 1985. A violent collapse of the atmosphere has occurred with a velocity of about 40 km s^–1 on October 1977, indicating a decrease of 0.07 AU in the radius for three days. A shrinking of the primary star is suggested from the characteristics of eclipse light curves that the duration of totality has become longer and the duration of eclipse shorter from eclipse to eclipse. The decrement of radius is estimated to be about 16%, 0.2 AU, in recent 27 years.     

Effect of vertical viscosity and diffusivity on tropical ocean circulation

Response of the tropical ocean to a uniform zonal wind is studied numerically and analytically. In addition to the Equatorial Undercurrent and surface westward flows on both sides of the equator, an eastward flow at the pycnocline depth is formed at several degrees latitude in both hemispheres. This subsurface eastward flow first appears in the eastern part of the ocean and extends to the west. Then it gradually decreases in speed, and at a steady state the speed is of the order of 1cm sec^–1. The spatial distribution of this subsurface flow is similar to the Subsurface Countercurrent, but the speed is one order smaller than that observed. The obtained thermostad is obscure compared with that observed. Whole of the time evolution produced by a numerical model can be accounted for by linear wave dynamics in a multi-layer model including vertical diffusion and friction. Although diffusion and friction are essential to maintain this subsurface flow, changes in the values of coefficients for vertical viscosity and diffusivity and also in initial density stratification lead only to a minor change in the speed of the subsurface eastward flow. It is concluded that a subsurface eastward flow with speed exceeding 10 cm sec^–1 accompanied by a distinctive thermostad structure cannot be explained by linear wave dynamics including vertical dissipation.     

Evapotranspiration from citrus trees growing in sandy soilunder drip irrigation with saline water

An experiment on evapotranspiration from citrus trees under irrigation with saline waterwas carried out for 4 months. Two lysimeters planted with a citrus tree in the green house wereused. One lysimeter was irrigated with saline water (NaCl and CaCl2 of 2000 mg/L equivalence,EC = 3.8 dS/m, SAR = 5.9) and the other was irrigated with freshwater using drip irrigation. Theapplied irrigation water was 1.2 times that of the evapotranspiration on the previous day.Evapotranspiration was calculated as the change in lysimeter weight recorded every 30 minutes.The lysimeters were filled with soil with 95.8% sand. The results of the experiment were as follows.(i) The evapotranspiration from citrus tree was reduced after irrigation with saline water. Theevapotranspiration returns to normal after leaching. However it takes months to exhaust the saltfrom the tree. ( ii ) To estimate the impact of irrigation with saline water on the evapotranspirationfrom citrus trees, the reduction coefficient due to salt stress (Ks) was used in this experiment.Evapotranspiration under irrigation with saline water (ETs) can be calculated from evapotranspira-tion under irrigation with freshwater (ET) by the equation ETs = Ks× ET. Ks can be expressed as afunction of ECsw. (iii) The critical soil-water electrical conductivity (ECsw) is 9.5 dS/m, beyondwhich adverse effects on evapotranspiration begin to appear. If ECsw can be controlled at below9.5 dS/m, saline water can be safely used for irrigation.     

Kosa (yellow sand) components in precipitation collected at central Japan

In east Asia, acidic gases derived from fossil fuel combustion have increased in the past decades. On the other hand, the Asian dust, also called Kosa (yellow sand) is transported following windstorms from arid lands in the Asian continent. Many researchers have been interested in the reaction between acidic aerosols and Kosa aerosols as well as the long-range transport of these emissions. To investigate the characteristics of chemical components in precipitation on a long-term basis over Japan, precipitation was sequentially collected from April 1984 to March 1997 at Kanazawa located near the coast of the Sea of Japan. Precipitation samples were collected at 1 mm intervals for the first 5 mm rainfall and all volume of rainwater after 6 mm for all precipitation events with an automatic wet only precipitation collector. According to the analyses of precipitation including Kosa aerosols during Kosa periods, the reaction in the air between Kosa and acidic components during the long-range transport was discussed.     

Seasonal variations in the nitrogen isotopic composition of settling particles at station K2 in the western subarctic North Pacific

Intensive observations using hydrographical cruises and moored sediment trap deployments during 2010 and 2012 at station K2 in the North Pacific Western Subarctic Gyre (WSG) revealed seasonal changes in δ ¹⁵N of both suspended and settling particles. Suspended particles (SUS) were collected from depths between the surface and 200 m; settling particles by drifting sediment traps (DST; 100–200 m) and moored sediment traps (MST; 200 and 500 m). All particles showed higher δ ¹⁵N values in winter and lower in summer, contrary to the expected by isotopic fractionation during phytoplankton nitrate consumption. We suggest that these observed isotopic patterns are due to ammonium consumption via light-controlled nitrification, which could induce variations in δ ¹⁵N(SUS) of 0.4–3.1 ‰ in the euphotic zone (EZ). The δ ¹⁵N(SUS) signature was reflected by δ ¹⁵N(DST) despite modifications during biogenic transformation from suspended particles in the EZ. δ ¹⁵N enrichment (average: 3.6 ‰) and the increase in C:N ratio (by 1.6) in settling particles suggests year-round contributions of metabolites from herbivorous zooplankton as well as TEPs produced by diatoms. Accordingly, seasonal δ ¹⁵N(DST) variations of 2.4–7.0 ‰ showed a significant correlation with primary productivity (PP) at K2. By applying the observed δ ¹⁵N(DST) vs. PP regression to δ ¹⁵N(MST) of 1.9–8.0 ‰, we constructed the first annual time-series of PP changes in the WSG. This new approach to estimate productivity can be a powerful tool for further understanding of the biological pump in the WSG, even though its validity needs to be examined carefully.     

Origin of sector trilling in cordierite in Daimonji hornfels,Kyoto, Japan

Sector trilling of cordierite in hornfels in the inner part of a contact aureole at Daimonji, Japan is a new type which consists not only of six (100) sectors (a-sectors) forming trilling, but also of (001) sectors (c-sectors) and high-index sectors (h-sectors). Complex twins within and among these sectors were studied from a viewpoint of a pseudo twin. The complex texture originated from both growth and transformation processes. The c-sector consists of three groups of domains which are related by a pseudo twin. This intrasector pseudo twin indicates that the initial phase of the c-sector was hexagonal cordierite (indialite) which later transformed to orthorhombic. The a-sector is related to adjacent sectors by a rotation of 120° around the c axis, resulting in an intersector pseudo twin. The a-sector is interpreted to have formed by overgrowth of orthorhombic cordierite on prism faces of indialite. The h-sector with the dendritic texture is also interpreted to have grown as orthorhombic cordierite. In hornfels in the middle part of the aureole, cordierites with sector trilling often coexist with single crystals of cordierite, and the sector trilling has no c- and h-sectors. This trilling type suggests that nucleation of indialite was subsequently followed by growth of orthorhombic cordierite in its stable field.     

The effects of crystallographic orientation,interface type and growth kinetics on Ni distribution between olivine and its melt

The effective distribution coefficient K _eff of Ni between solid and liquid has been experimentally determined as a function of growth rates and crystallographic orientations for (Mg, Ni)₂SiO₄ crystals grown by the floating-zone method. Crystals were grown by the continuous mechanism at slow rates, but were faceted at high rates, which enables us to determine the dependence of K _eff on orientations and on smooth versus rough interfaces. It has been verified that K _eff of Ni becomes larger than the equilibrium value K _o as the growth rate increases and that K _eff of faceted «110» directions is larger than that of non-faceted higher index directions. The results can be qualitatively explained by the theories which treat the distribution of elements in relation to growth kinetics. Element distribution during the recovery process from rounded to faceted morphology is also analysed in detail.     

Interannual and interdecadal variabilities in the Pacific in an MRI coupled GCM

Interannual and interdecadal variabilities in the Pacific are investigated with a coupled atmosphere-ocean GCM developed at MRI, Japan. The model is run for 70 years with flux adjustments. The model shows interannual variability in the tropical Pacific which has several typical characteristics shared with the observed ENSO. A basin-scale feature of the principal SST variation for the ENSO time scale shows negative correlation in the central North Pacific with the tropical SST, similar to that of the observed one. Associated variation of the model atmosphere indicates an intensification of the Aleutian Low and a PNA-like teleconnection pattern as a response to the tropical warm SST anomaly. The ENSO time scale variability in the midlatitude ocean consists of the westward propagation of the subsurface temperature signal and the temperature variation within the shallow mixed layer forced by the anomalous atmospheric heat fluxes. For the interdecadal time scale, variation of the SST is simulated realistically with a geographical pattern similar to that for the ENSO time scale, but it has a larger relative amplitude in the northern Pacific. For the atmosphere, spatial structure of the variation in the interdecadal time scale is also similar to that in the ENSO time scale, but has smaller amplitude in the northern Pacific. Long oceanic spin-up time (>∼10 y) in the mid-high latitude, however, makes oceanic response in the interdecadal time scale larger than that in the ENSO time scale. The lagged-regression analysis for the ocean temperature variation relative to the wind stress variation indicates that interdecadal variation of the ocean subsurface at the mid-high latitudes is considered as enhanced ocean gyre spin-up process in response to the atmospheric circulation change at the mid-high latitudes, remotely forced by the interdecadal variation of the tropical SST. Received: 6 November 1995 / Accepted: 19 April 1996     

Evapotranspiration from citrus trees growing in sandy soil under drip irrigation with saline water

An experiment on evapotranspiration from citrus trees under irrigation with saline water was carried out for 4 months. Two lysimeters planted with a citrus tree in the green house were used. One lysimeter was irrigated with saline water (NaCl and CaCl₂ of 2000 mg/L equivalence,EC = 3.8 dS/m, SAR = 5.9) and the other was irrigated with freshwater using drip irrigation. The applied irrigation water was 1.2 times that of the evapotranspiration on the previous day. Evapotranspiration was calculated as the change in lysimeter weight recorded every 30 minutes. The lysimeters were filled with soil with 95.8% sand. The results of the experiment were as follows. (i) The evapotranspiration from citrus tree was reduced after irrigation with saline water. The evapotranspiration returns to normal after leaching. However it takes months to exhaust the salt from the tree. (ii) To estimate the impact of irrigation with saline water on the evapotranspiration from citrus trees, the reduction coefficient due to salt stress (K_s) was used in this experiment. Evapotranspiration under irrigation with saline water (ET _s ) can be calculated from evapotranspiration under irrigation with freshwater (ET) by the equationET _s =K _s × ET. K_s can be expressed as a function ofEC _sw . (iii) The critical soil-water electrical conductivity (EC _sw ) is 9.5 dS/m, beyond which adverse effects on evapotranspiration begin to appear. IfEC _sw can be controlled at below 9.5 dS/m, saline water can be safely used for irrigation.