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11.
The rôle of thermodynamics in the oceanic general circulation is investigated. The ocean is regarded as an open dissipative system that exchanges heat and salt with the surrounding system. A new quantitative method is presented to express the rate of entropy increase for a large‐scale open system and its surroundings by the transports of heat and matter. This method is based on Clausius's definition of thermodynamic entropy, and is independent of explicit expressions of small‐scale dissipation processes. This method is applied to an oceanic general circulation model, and the entropy increase rate is calculated during the spin‐up period of the model. It is found that, in a steady‐state, the entropy increase rate of the ocean system is zero, whereas that of the surroundings shows positive values, for both heat and salt transports. The zero entropy increase rate of the ocean system represents the fact that the system is in a steady‐state, while the positive entropy increase rate in the surroundings is caused by irreversible transports of heat and salt through the steady‐state circulation. The calculated entropy increase rate in the surroundings is 1.9×1011 W K−1 , and is primarily due to the heat transport. It is suggested that the existence of a steady‐state dissipative system on the Earth, from a living system to the oceanic circulation, has a certain contribution to the entropy increase in its nonequilibrium surroundings. 相似文献
12.
Abstract— The role of oxygen isotope exchange during evaporation and condensation of silicate melt is quantitatively evaluated. Silicate dusts instantaneously heated above liquidus temperature are assumed to cool in gas and experience partial evaporation and subsequent recondensation. The results show that isotopic exchange effectively suppresses mass‐dependent O‐isotope fractionation even if the degree of evaporation is large, which is the fundamental difference from the case without isotopic exchange. The final composition of silicate melt strongly depends on the initial abundance of oxygen in the ambient gas relative to that in silicate dust, but not on the cooling rate of the system. The model was applied to O‐isotope evolution of silicate melts in isotopically distinct gas of the protoplanetary disk. It was found that deviation from a straight mixing line toward the δ18O‐rich side on the three‐oxygen isotope diagram is inevitable when mass‐dependent fractionation and isotopic exchange take place simultaneously; the degree of deviation depends on the abundance of oxygen in an ambient gas and isotopic exchange efficiency. The model is applied to explain O‐isotopic compositions of igneous CAIs and chondrules. 相似文献
13.
Young-Hee Lee Hee-Jeong Lim Kazuhito Ichii Yingnian Li 《Asia-Pacific Journal of Atmospheric Sciences》2013,49(5):561-570
The Tibetan plateau plays an important role in energy and carbon cycles by providing an elevated heat source and by storing a large amount of soil carbon due to low temperature. The main vegetation of the plateau is alpine grassland. This study evaluates performance of Community Land Model 3.5 with carbon and nitrogen cycles (CLM3.5CN) over a alpine grassland in the Tibetan plateau in terms of energy and carbon fluxes in conditions of reasonable phenology and initial carbon pool comparable to observations. Comparison between model and observation shows following features. The model captures the magnitude of maximum leaf area index (LAI) but underestimats leaf mass. Net ecosystem exchange (NEE) is significantly underestimated during the growing season and soil temperature is also underestimated throughout a year with higher negative bias in winter than in other seasons. In order to examine the cause of the model deficiencies, we design four sensitivity tests: seasonal mulch; shallow rooting depth; reduction of critical soil moisture to limit the decomposition rate; smaller specific leaf area (SLA). Considering seasonal mulch improves the negative bias of soil temperature during dormant season has little effect on the NEE during the growing seasson. Underestimation of NEE during the growing season is partly due to underestimated decomposition rate which results from underestimated soil temperature and deep root placement in the soil column. Underestimation of latent heat flux during summer is partly due to use of large SLA in the model. Other deficiencies are also discussed. 相似文献
14.
MENZIES M.; OBATA M.; ARAI S.; BODINIER J.-L.; KOHLSTEDT D.; FREY F.; OZAWA K.; SHIMIZU N.; VISSERS R. 《Journal of Petrology》2004,45(2):221-222
The papers in this thematic issue of Journal of Petrology weredelivered at the Fourth International Workshop on Orogenic Lherzolitesand Mantle Processes, which was held in Samani, Hokkaido, Japan,between August 26 and September 3, 2002. Fifty oral presentationswere given and 45 posters were displayed during the meeting,and the research papers in this issue provide an 相似文献
15.
Masaaki Obata Kazuhito Ozawa Kosuke Naemura Akira Miyake 《Mineralogy and Petrology》2013,107(6):881-895
An isochemical kelyphite (orthopyroxene+spinel+plagioclase) that has nearly the same bulk chemical composition as the precursor garnet was found within a matrix of ordinary kelyphites (orthopyroxene+clinopyroxene+spinel±amphibole) in garnet peridotites from the Czech part of the Moldanubian Zone. It was shown that the kelyphitization of garnet took place in three stages: (1) the garnet-olivine reaction, accompanied by a long-range material transfer across the reaction zone, and (2) the isochemical breakdown of garnet, essentially in a chemically-closed system, and finally, (3) an open-system hydration reaction producing a thin hydrous zone (amphibole+spinel+plagioclase), which is located between the isochemical kelyphite and relict garnet. The presence of relict garnet suggests that this breakdown reaction of the second stage did not proceed to a completion probably being hindered by the formation of the hydrous zone at the reaction front. It was found by electron back-scattered diffraction method that orthopyroxene and spinel do not show any topotaxic relationship in the first type of kelyphite; whereas they show locally topotaxic relationship in the isochemical kelyphite. The transition from the first type to the second type of kelyphite is discussed on the basis of the detailed observations in the transition zone between the two kelyphites. More widespread occurrence of isochemical kelyphite is expected to occur in orogenic peridotites as well as from xenoliths brought by volcanics. 相似文献
16.
Modeling the interannual variability and trends in gross and net primary productivity of tropical forests from 1982 to 1999 总被引:1,自引:0,他引:1
Kazuhito Ichii Hirofumi Hashimoto Ramakrishna Nemani Michael White 《Global and Planetary Change》2005,48(4):314
The role of tropical ecosystems in global carbon cycling is uncertain, at least partially due to an incomplete understanding of climatic forcings of carbon fluxes. To reduce this uncertainty, we simulated and analyzed 1982–1999 Amazonian, African, and Asian carbon fluxes using the Biome-BGC prognostic carbon cycle model driven by National Centers for Environmental Prediction reanalysis daily climate data. We first characterized the individual contribution of temperature, precipitation, radiation, and vapor pressure deficit to interannual variations in carbon fluxes and then calculated trends in gross primary productivity (GPP) and net primary productivity (NPP). In tropical ecosystems, variations in solar radiation and, to a lesser extent, temperature and precipitation, explained most interannual variation in GPP. On the other hand, temperature followed by solar radiation primarily determined variation in NPP. Tropical GPP gradually increased in response to increasing atmospheric CO2. Confirming earlier studies, changes in solar radiation played a dominant role in CO2 uptake over the Amazon relative to other tropical regions. Model results showed negligible impacts from variations and trends in precipitation or vapor pressure deficits on CO2 uptake. 相似文献
17.
Processes of crystal separation in a magma heavily laden withcrystals without phase change are investigated from observationson frozen magma systems: Nosappumisaki and other shoshoniteintrusions in the Nemuro peninsula, Japan, for which the originof the crystals and the initial conditions are well constrained.The Nosappumisaki intrusion is 120 m in thickness and extendsfor more than 1·5 km. It exhibits a wide range of lithologicalvariation, principally as a result of crystal redistributionafter intrusion. Crystals in each lithology can be clearly dividedinto two kinds according to their composition and texture: thosepresent before the intrusion of the magma (phenocrysts)and those that crystallized in situ after intrusion. From thevertical change in mode and size of phenocrysts,it is shown that (1) augite phenocrysts were rapidlydeposited, with little overgrowth after intrusion, by significantcoagulation or clustering on a time-scale of more than a fewyears, and (2) plagioclase phenocrysts, definitelydenser than the melt but concentrated in the upper level, floatedby counter flow of massive deposition of augite phenocrysts.These results indicate that in a magma heavily laden with crystalsof a few millimeters in size (>20 vol. %), crystalcrystaland crystalmelt interaction play an important role inthe separation of crystals from the host melt. KEY WORDS: magma chamber; sill; crystal settling; plagioclase flotation; Nosappumisaki 相似文献
18.
We considered the two-dimensional stress aspect of a fault from the viewpoint of differential geometry. For this analysis,
we concentrated on the curvatures of the Airy stress function surface. We found the following: (i) Because the principal stresses
are the principal curvatures of the stress function surface, the first and the second invariant quantities in the elasticity
correspond to invariant quantities in differential geometry; specifically, the mean and Gaussian curvatures, respectively;
(ii) Coulomb’s failure criterion shows that the coefficient of friction is the physical expression of the geometric energy
of the stress function surface; (iii) The differential geometric expression of the Goursat formula shows that the fault (dislocation)
type (strike-slip or dip-slip) corresponds to the stress function surface type (elliptic or hyperbolic). Finally, we discuss
the need to use non-biharmonic stress tensor theory to describe the stress aspect of multi-faults or an earthquake source
zone. 相似文献
19.
Kazuhito Yamasaki 《Acta Geophysica》2009,57(3):567-582
We consider the effect of the faults-defects (FD) field on the following quantum phenomena: (i) the motion of a particle expressed
by the Green function; (ii) thermodynamic phenomena expressed by the partition function. We use the path integral formulation
based on the extended deformation gradient (EDG) tensor. This formulation connects the Green function of (i) with the partition
function of (ii) to describe the thermodynamics in terms of a quantum particle motion. We obtain the following results: (a)
The Lagrangian in the Green function includes the new potential consisting of stress functions that shift the path of the
free particle from the shortest distance; (b) The solution of the partition function in one-dimensional space makes it possible
to deduce the thermodynamic relations in the FD field. Such results could not be obtained by taking the traditional mechanical
and quantum approaches, so the path integral formulation based on the EDG tensor is a useful tool. 相似文献
20.
A two-dimensional stress field of dislocation or fault is geometrically studied for an asymmetric continuum. For geometric surfaces of the stress and couple-stress functions, the mean and Gaussian curvatures are derived. The mean curvature of couple-stress function surface is connected with the asymmetric of stress tensor. Moreover, the Gaussian curvature of stress function surface is characterized by both the stress and couple-stress. On the other hand, the mean curvature of stress function surface is not affected by the asymmetry of stress. Based on these geometric expressions, the Coulomb’s failure criterion and the friction coefficient are expressed by the curvatures of couple-stress function surface. Moreover, geometric structures of stress and couple stress function surfaces are shown for edge and wedge dislocations as faults. The curvatures of these surfaces show that the effect of couple-stress is constrained around the dislocations only. 相似文献