Moderately stable flow over a three-dimensional hill A comparison of linear theory with laboratory measurements     

ROGER S. THOMPSON  MICHAEL S. SHIPMAN  JAMES W. ROTTMAN 《地球，A辑:动力气象学与海洋学》1991,43(1):49-63

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Annual variation of the global precipitable water and its maintenance: observation and climate-simulation     

TSING-CHENG CHEN  MING-CHANG YEN  JAMES PFAENDTNER  Y. C. SUD 《地球，A辑:动力气象学与海洋学》1996,48(1):1-16

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Age determination of intermoraine areas, Austerdalen, southern Norway     

JUDITH K. MAIZELS  JAMES R. PETCH 《Boreas: An International Journal of Quaternary Research》1985,14(1):51-65

This paper is concerned with the size variation of thalli of the lichen Rhizocarpon geographicum agg. on intermoraine surfaces in the proglacial valley of Austerdalen, southern Norway, and with the use of thallus dimensions for both relative and absolute dating of intermoraine deposits. Measurements of the five largest lichens in 200 m² search areas at 255 sites show significant cross-valley and down-valley variations, with the smallest thalli located towards the centre of the valley and at up-valley sites. This variation has been examined in greater detail by dividing the intermoraine areas into twelve morphological zones, for which geomorphological and stratigraphical relations enable the construction of a relative time sequence of formation. This relative time sequence was then found to he confirmed by mean values of measurements of the largest lichen thalli in 100 m square quadrats within each morphological zone. This approach has allowed not only the relative age of morainic and intermorainic deposits to he established from geomorphological evidence but also, using tentative dates for the moraines, the construction of a chronology of moraine and intermoraine depositional events.  相似文献   

Relation of atmospheric CO₂ to tropical sea and air temperatures and precipitation     

WILLIAM P. ELLIOTT  JAMES K. ANGELL  KIRK W. THONING 《Tellus. Series B, Chemical and physical meteorology》1991,43(2):144-155

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The orientation of helical flow in curved channels     

RANSOME K. T. CORNEY†  JEFFREY PEAKALL  DANIEL R. PARSONS  LIONEL ELLIOTT†  KATHRYN J. AMOS  JAMES L. BEST  GARETH M. KEEVIL  DEREK B. INGHAM† 《Sedimentology》2006,53(2):249-257

The planform patterns of meandering submarine channels and subaerial fluvial bends show many similarities that have given rise to strong analogies concerning the fluid dynamics of these channel types. Existing models of helical motion in open‐channel bends depict flow that is characterized by surface flow towards the outer bank, and basal flow towards the inner bank. This paper investigates and compares, through an analytical model and physical experiment, flows within fluvial meanders, and submarine channel bends that contain density‐driven gravity currents. The results indicate that the sense of helical motion can be reversed in submarine bends that contain density currents when compared with fluvial bends, and that the orientation of the helical flow is dependent on the vertical distribution of downstream velocity. Specifically, the sense of helical motion is reversed in bends when the maximum downstream velocity is near the bed, resulting in near‐bed flow towards the outer bank. These findings suggest that the dynamics of sediment transport and deposition in curved channels with such velocity profiles will be fundamentally different to those currently assumed from sinuous open‐channels.  相似文献   

Aeolian saltation threshold: the effect of density ratio   总被引：2，自引：0，他引：2  

JAMES D. IVERSEN  RONALD GREELEY  JOHN R. MARSHALL  JAMES B. POLLACK 《Sedimentology》1987,34(4):699-706

Saltation threshold data from three wind tunnels and from hydraulic flumes are presented to show that the dimensionless threshold friction speed for small particles is a continuous function of particle-to-fluid-density ratio. In addition, the dimensionless threshold speed is a function of the grain-friction Reynolds number and an interparticle force term. The variation with density ratio seems to be due to the relative energy with which particles impact other particles to initiate saltation.  相似文献   

Zoned calcites in Jurassic ammonite chambers: trace elements, isotopes and neomorphic origin     

JAMES D. MARSHALL 《Sedimentology》1981,28(6):867-887

Zoned calcites were found in the phragmacone chambers of three Sonniniid ammonites from marine Middle Jurassic sandstones (Isle of Skye, U.K.). Each ammonite has a unique sequence of up to nine zones of calcite which fill or partially fill the chambers. Zones are defined by changes in the density of minute opaque inclusions and variation in trace-element composition. Proximal (early) calcites have undulose extinction and some exhibit the specific fabrics of fascicular-optic and radiaxial fibrous calcites. Microdolomite inclusions are found in one specimen. Early calcites, interpreted as replacements after a single isopachous fringe of acicular carbonate (probably high magnesium calcite), are succeeded by blocky ferroan calcite cement. In one specimen there are two distinct generations of calcite, in the others there is a continuous mosaic incorporating both early calcites and late cement. Isotopic composition of the early calcite zones demonstrates the initial importance of organic derived carbon (δ¹³C =— 26‰, δ¹⁸O ‰ O). Further cementation and mineralogical stabilization took place at increased temperatures and probably after modification of the pore water isotopic composition (calcites with δ¹³C =— O‰, δ¹⁸O～— 10‰). The distinctive fabrics and zonal patterns probably developed during the replacement of the precursor cement and are not primary growth features. Reversals in isotopic and trace element trends are believed to be related to the rate of neomorphic crystal growth and hence to the degree of exchange with external pore waters. Further increase in temperature, probably during Tertiary igneous activity, gave rise to the extremely light δ¹⁸O values of the late cements in the ammonite which had previously had least contact with external waters (cements with δ¹³C ～ O, δ¹⁸O ～— 20‰).  相似文献   

Climate change impacts on Namibia's natural resources and economy     

HANNAH REID  LINDA SAHLéN  JESPER STAGE  JAMES MACGREGOR 《Climate Policy》2013,13(5):452-466

Climate change is likely to exacerbate the dry conditions already experienced in southern Africa. When rainfall does come, it is likely to be in bursts of greater intensity, leading to erosion and flood damage. However, these predictions have had very little influence on policy in southern African countries. Computable general equilibrium (CGE) model simulations for Namibia indicate that over 20 years, annual losses to the Namibian economy could be up to 5% of GDP, due to the impact that climate change will have on its natural resources alone. This will affect the poorest people the most, with resulting constraints on employment opportunities and declining wages, especially for unskilled labour in rural areas. Namibia must take steps to ensure that all its policies and activities are ‘climate proofed’ and that it has a strategy to deal with displaced farmers and farm workers. The need to mainstream climate change into policies and planning is clear, and it is the responsibility of industrialized nations, who have largely created the problem of climate change, to help Namibia and other vulnerable countries cope with climate change impacts and plan for a climate-constrained future.  相似文献   

ENVIRONMENTALISM AND EUROCENTRISM     

JAMES M. BLAUT 《Geographical review》1999,89(3):391-408

ABSTRACT. Environmental determinism has served to validate a Eurocentric world history for several centuries, and it continues to do so today. This essay looks briefly at the historical marriage between environmental determinism and Eurocentric history, then develops a detailed critique of the environmental determinism put forward in two recent world-history books: Jared Diamond's Guns, Germs, and Steel (1997) and David Landes's The Wealth and Poverty of Nations (1998).  相似文献   

Book Review: SOILS AND ENVIRONMENT by S. Ellis and A. Mellor. Routledge, 1995. 364 pp. £55.00 ($82.50) (hbk), £16.99 ($25.50) (pbk). ISBN 0 415 06887 8 (hbk); 415 06888 8 (pbk)     

PETER JAMES 《Geological Journal》1997,32(2):194-194

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