GIS and quantitative geography

The purpose of this paper is to explore the development of the GIS revolution within the field of geography in the 1980s and 1990s, taking into consideration the influence of external and internal factors on disciplinary change. Geography is rapidly changing by the impact of external factors on geographical research and also as a consequence of economic recession and cutbacks in higher education. Most geography departments in universities have tried to approach this impact by promoting or shifting to human geography as an applied science, and by offering relevant skills through GIS as an approach to contemporary problems. It is concluded that quantitative geography is essential for the further expansion of GIS within geography and also for the survival of geography. This revised version was published online in July 2006 with corrections to the Cover Date.     

Upwelling of oxygen-depleted water (Sumishio) in Omura Bay,Japan

Wind-induced circulation and the distribution of hypoxia corresponding to the upwelling of oxygen-depleted water (called “Aoshio” in Japan and “Sumishio” locally in Omura Bay) in Omura Bay, Japan, was examined field observations and by three-dimensional modeling. During the calm weather in summer, well-mixed strait water, in rich oxygen at the mouth of the bay intruded into the middle layer of the bay, southward and northward along the west and east coast, respectively, forming basin-scale cyclonic circulation. A stagnant water mass was formed below the center of this cyclonic circulation, and it became hypoxic water. As a result of the prevailing strong southeast (northeast) wind, the bottom hypoxia moved in a southeasterly (northeasterly) direction. This induces the upwelling of hypoxic water, accompanied by mass mortality of marine organisms.     

Polarized infrared absorbance spectra of an optically anisotropic crystal: Application to the orientation of the OH- dipole in quartz

The polarized infrared (IR) absorbance spectrum was formulated for an optically anisotropic crystal under the conditions of Fourier transform microspectroscopy. The adequacy of this formulation was confirmed by comparison of calculated interference fringes with those observed in polarized absorbance spectra of optically anisotropic crystal. In accordance with the formulated absorbance, an experimental constraint for the correct measurement of polarized IR absorbance spectrum of optically anisotropic crystal is proposed. Under this experimental constraint, polarized IR absorbance spectra of quartz from Arkansas were measured. They show that the orientation of OH^- dipole which compensates the charge balance coupled with Al³⁺ in quartz is highly polarized perpendicular to the c-axis.     

A multilayer model for thermal infrared emission of Saturn’s rings II: Albedo, spins, and vertical mixing of ring particles inferred from Cassini CIRS

Since the Saturn orbit insertion of the Cassini spacecraft in mid-2004, the Cassini composite infrared spectrometer (CIRS) measured temperatures of Saturn’s main rings at various observational geometries. In the present study, we apply our new thermal model (Morishima, R., Salo, H., Ohtsuki, K. [2009]. Icarus 201, 634-654) for fitting to the early phase Cassini data (Spilker, L.J., and 11 colleagues [2006]. Planet. Space Sci. 54, 1167-1176). Our model is based on classical radiative transfer and takes into account the heat transport due to particle motion in the azimuthal and vertical directions. The model assumes a bimodal size distribution consisting of small fast rotators and large slow rotators. We estimated the bolometric Bond albedo, A_V, the fraction of fast rotators in cross section, f_fast, and the thermal inertia, Γ, by the data fitting at every radius from the inner C ring to the outer A ring. The albedo A_V is 0.1-0.4, 0.5-0.7, 0.4, 0.5 for the C ring, the B ring, the Cassini division, and the A ring, respectively. The fraction f_fast depends on the ratio of scale height of fast rotators to that of slow rotators, h_r. When h_r = 1, f_fast is roughly half for the entire rings, except for the A ring, where f_fast increases from 0.5 to 0.9 with increasing saturnocentric radius. When h_r increases from 1 to 3, f_fast decreases by 0.2-0.4 for the B and A rings while no change in f_fast is seen for the optically thin C ring and Cassini division. The large f_fast seen in the outer A ring probably indicates that a large number of small particles detach from large particles in high velocity collisions due to satellite perturbations or self-gravity wakes. The thermal inertia, Γ, is constrained from the efficiency of the vertical heat transport due to particle motion between the lit and unlit faces, and is coupled with the type of vertical motion. We found that in most regions, except for the mid B ring, sinusoidal vertical motion without bouncing is more reasonable than cycloidal motion assuming bouncing at the midplane, because the latter motion gives too large Γ as compared with previous estimations. For the mid B ring, where the optical depth is highest in Saturn’s rings, cycloidal vertical motion is more reasonable than sinusoidal vertical motion which gives too small Γ.     

Millennial-scale vegetation changes during the last 40,000 yr based on a pollen record from Lake Biwa, Japan

A high-resolution pollen record covering the last 40,000 yr (BIW95-4) from Lake Biwa, western Japan, shows regional vegetation responses to millennial-scale climate changes. From 40 to 30 ka, Cryptomeria japonica was dominant around the lake among pinaceous conifers and deciduous broad-leaved trees. During this period, fluctuations of C.japonica are correlated with Dansgaard-Oeschger (D-O) cycles recognized from the anhysteretic remanent magnetization (ARM) record. Increases in the abundance of this taxon may have been caused by wetter summer conditions influenced by the East Asian monsoon or increased snowfall on the Sea of Japan side of the Japanese archipelago. Between 29 and 14 ka, pinaceous conifer forests mainly composed of Pinus subgenus Haploxylon, Tsuga, and Picea trees developed. At approximately 23 ka, Picea trees increased in abundance as ARM values decreased. This expansion of Picea trees has been correlated with Heinrich event (HE) 2 in the North Atlantic. At about 14 ka, the distribution of broad-leaved forest (mainly composed of deciduous oaks) began to expand after D-O 1. Evidence of significant vegetation change related to the abrupt Younger Dryas cooling event has not been found.     

Proton migration in portlandite inferred from activation energy of self-diffusion and potential energy curve of OH bond

A fundamental mechanism on the atomic level for self-diffusion in the proton layer of portlandite, Ca(OH)₂, was investigated by conducting hydrogen–deuterium (H–D) exchange diffusion experiments and by deriving potential energy curves of OH vibrations from optical absorption measurements. Synthetic single crystals of portlandite were used in H–D experiments between 250 and 450°C at 150 MPa. Arrhenius parameters for proton diffusion perpendicular to the c-axis gave a frequency factor of 1.0 × 10⁻¹⁰ m²/s and activation energy of 0.61 eV (58.5 kJ/mol). The activation energy corresponds to the height of the potential barrier between two oxygen atoms across an interlayer. The potential barrier height was also theoretically estimated using the OH potential energy curve (OH-PEC) determined by optical absorption measurements. Experimental and theoretical results suggest that the potential barrier height cannot be simply determined by overlapping two OH-PECs. The potential barrier derived theoretically was 3.11 eV. This is too high for the activation energy of the proton diffusion. It implies that the interaction between a diffusing proton and the vacancy of a proton site, and the shortening of interlayer oxygen distance by thermal vibration reduce the potential barrier.     

Visible and near-infrared spectral survey of Martian meteorites stored at the National Institute of Polar Research

Martian meteorite chip samples stored at the National Institute of Polar Research (NIPR) have been studied by a visible and near-infrared (VNIR) spectrometer. Measured spots are about 3 × 2 mm in size, which are clearly marked on photographs of the meteorite chips. Rock types and approximate mineral compositions of studied meteorites have been identified or obtained through this spectral survey with no sample preparation required. This study demonstrates that this kind of spectral survey is effective in classifying and describing Marian meteorites, and that such a VNIR spectrometer on a Mars rover would be useful for identifying these kinds of unaltered Mars rocks. Further studies which utilize a smaller spot size are desired for improving the accuracy of identifying the clasts and mineral phases in the rocks.     

Rotation rate and velocity dispersion of planetary ring particles with size distribution: I. Formulation and analytic calculation

We derive an equation for the evolution of rotational energy of Keplerian particles in a dilute disk due to mutual collisions. Three-dimensional Keplerian motion of particles is taken into account precisely, on the basis of Hill's approximation. The Rayleigh distribution of particles' orbital eccentricities and inclinations, and the Gaussian distribution of their rotation rates are also taken into account. Performing appropriate variable transformation, we show that the equation can be expressed with two terms. The first term, which we call collisional stirring term, represents energy exchange between rotation and random motion via collisions. The second term, which we call rotational friction term, tends to equalize the mean rotational energy of particles with different sizes. The equation can describe the evolution of rotational energy of Keplerian particles with an arbitrary size distribution. We analytically evaluate the rates of stirring and friction for the random kinetic energy and rotational energy due to inelastic collisions, for non-gravitating particles in a dilute disk. Using these results, we discuss equilibrium states in a disk of spinning, non-gravitating Keplerian particles.     

Petrology and geochemistry of a silicate clast from the Mount Padbury mesosiderite: Implications for metal‐silicate mixing events of mesosiderite

Abstract— Petrological and bulk geochemical studies were performed on a large silicate clast from the Mount Padbury mesosiderite. The silicate clast is composed mainly of pyroxene and plagioclase with minor amounts of ilmenite, spinel, and other accessory minerals, and it shows subophitic texture. Pyroxenes in the clast are similar to those in type 5 eucrites and could have experienced prolonged thermal metamorphism after rapid crystallization from a near‐surface melt. Ilmenite and spinel vary chemically, indicating growth under disequilibrium conditions. The clast seems to have experienced an episode of rapid reheating and cooling, possibly as a result of metal‐silicate mixing. Abundances of siderophile elements are obviously higher than in eucrites, although the clast is also extremely depleted in highly siderophile elements. The fractionated pattern can be explained by injection of Fe‐FeS melts generated by partial melting of metallic portions during metal‐silicate mixing. The silicate clast had a complex petrogenesis that could have included: 1) rapid crystallization from magma in a lava flow or a shallow intrusion; 2) prolonged thermal metamorphism to equilibrate the mineral compositions of pyroxene and plagioclase after primary crystallization; 3) metal‐silicate mixing probably caused by the impact of solid metal bodies on the surface of the mesosiderite parent body; and 4) partial melting of metal and sulfide portions (and silicate in some cases) caused by the collisional heating, which produced Fe‐FeS melts with highly fractionated siderophile elements that were injected into silicate portions along cracks and fractures.     

A GIS-based study toward forecast of suburban forest change

At a time when the concept of ‘human and environmental symbiosis’ has taken on much significance, protection of suburban forests (i.e. forests adjacent to or near developed areas) is a topic that has drawn much attention. Suburban forests have, since ancient times, been places where people have gathered firewood and cultured trees. As a result, the vegetation of suburban forests is only partially natural and continues to change as the forms of human activity in and around them changes. Accurate forecasts of how suburban forests will change are, therefore, an important element in the debate over how to protect them. In this study, a suburban forest was analyzed with laser radar sensing, multi-spectrum scanning, digital photogrammetry analysis, aerial photograph interpretation, and a field survey. Data gathered using these techniques were compiled on a GIS to forecast future changes in the forest. Aerial photographs taken over the past 50 years were analyzed to illuminate changes in the forest over that period. Specifically, comparisons of precise Digital Elevation Models (DEMs) measured by using digital photogrammetry workstations made it possible to estimate growth in forest height. The possible future conversion of such results to estimates of amounts of carbon dioxide consolidated by forests should be very significant for discussions of global environmental problems. This revised version was published online in July 2006 with corrections to the Cover Date.