Can an atmospherically forced ocean model accurately simulate sea surface temperature during ENSO events?     

By A. BIROL KARA  HARLEY E. HURLBURT  CHARLIE N. BARRON  ALAN J. WALLCRAFT  E. JOSEPH METZGER 《地球，A辑:动力气象学与海洋学》2010,62(1):48-61

The performance of an atmospherically forced ocean general circulation model (OGCM) in simulating daily and monthly sea surface temperature (SST) is examined during the historical El Niño Southern Oscillation (ENSO) events during the time period 1993–2003. For this purpose, we use the HYbrid Coordinate Ocean Model (HYCOM) configured for the North Pacific north of 20°S at a resolution of ≈9 km. There is no assimilation of (or relaxation to) SST data and no date-specific assimilation of any data type. The ability of the model in simulating temporal variations of SST anomalies is discussed by comparing model results with two satellite-based SST products. The HYCOM simulation gives a basin-averaged monthly mean bias of 0.3 °C and rms difference of 0.6 °C over the North Pacific Ocean during 1993–2003. While the model is able to simulate SST anomalies with mean biases  <0.5 °C  in comparison to observations during most of the ENSO events, limitations in the accuracy of atmospheric forcing (specifically, net short-wave radiation) have some influence on the accuracy of simulations. This is specifically demonstrated during the 1998 transition period from El Niño to La Niña, when a record large SST drop of  ≈7 °C  occurred in the eastern equatorial Pacific Ocean.  相似文献   

THE GEOGRAPHICAL DIMENSIONS OF AL‐QA'IDA RHETORIC     

JOSEPH J. HOBBS 《Geographical review》2005,95(3):301-327

ABSTRACT. This article examines the geographical ideology of al‐Qa'ida. The central questions are to what extent al‐Qa'ida terrorism is motivated by a desire to control geographical space, and how the organization defines that space as place in its communiqués. The study also asks whether al‐Qa'ida's geographical rhetoric reveals the nature or locations of future attacks. Principal sources are statements and interviews by and with al‐Qa'ida leaders. al‐Qa'ida classifies distinctive geographical realms of legitimization, preparation, and action. Its geographical concerns and ambitions are hierarchical and based principally on perceptions of sacred space. The holy places of Mecca, Medina, and Jerusalem are the cornerstones of a greater Islamic holy land that al‐Qa'ida seeks to rid of non‐Islamic‐especially U.S. and “Zionist”‐elements and replace with a new caliphate. Terrorism directed principally against American civilians in the United States is one of the main tactics by which al‐Qa'ida says it hopes to achieve its goals in geographical space.  相似文献   

THEORETICAL ANALYSIS OF AN IMPERVIOUS,HEATED-CYLINDER ‘GROUNDWATER VELOCIMETER’     

JOSEPH R. FELDKAMP 《国际地质力学数值与分析法杂志》1996,20(11):815-830

An isothermally heated, impervious cylinder, which is placed normal to the path of flowing groundwater, is theoretically evaluated for its potential to serve as a kind of ‘groundwater velocimeter’. The essential task is to determine whether the variation in heat output along the cylinder perimeter is sufficiently large to permit measurement for typical groundwater velocities. Using finite elements, the governing equations of advective thermal transport in saturated porous media are solved to obtain the variation in heat output along the circumference of the heated cylinder. An annular region of different hydraulic conductivity is assumed to separate the cylinder from the surrounding formation. The creation of such a region during placement of a cylinder is inevitable. A parametric study led to the following conclusions: (1) A smaller cylinder radius is preferable since the time to achieve a particular degree of asymmetry in heat output is then greatly reduced. (2) An annular region of lower hydraulic conductivity, relative to formation, reduces output asymmetry by no more than 25%, but if hydraulic conductivity is increased, output asymmetry can increase several times. (3) For annular regions having a higher hydraulic conductivity than the surrounding formation, annular thickness is not important. (4) The least groundwater speed which may be accurately measured by such a device will depend heavily upon instrumentation but is tentatively placed at about 5⋅0×10⁻⁵ cm/s. Theoretical results are approximately confirmed by preliminary experiments with a prototype device which has been constructed so as to directly measure the expected variation in thermal output. Partial construction details are provided.  相似文献   

Population Dynamics and Settlement Systems     

LEX CHALMERS  ALUN JOSEPH 《New Zealand geographer》1997,53(1):14-21

The paper uses five broad classes of settlement in the Waikato as a base for exploring age and gender specific changes to population distributions. The trends are assessed over the period 1981 to 1991, an era of significant change to the economic and social fabric of the region. Links between this change and the inferred patterns of movement are suggested. Notable patterns include migration deficits in the youthful and elderly age classes in sparsely settled rural areas, and more substantial numbers of elderly in other non metropolitan settlements than expected. The policy implications of these distributions are considered in the concluding section of the paper.  相似文献   

Geochemistry of an Island-Arc Plutonic Suite: the Uasilau-Yau Yau Intrusive Complex, New Britain, P.N.G   总被引：2，自引：0，他引：2  

WHALEN  JOSEPH B. 《Journal of Petrology》1985,26(3):603-632

In the Uasilau-Yau Yau intrusive complex of central New Britain,Papua New Guinea, there is a compositional continuum in intrusiverock-types from gabbro to granodiorite and K-Ar mineral agesof the most mafic and most felsic components are not significantlydifferent (29?0.6 Ma versus 28.3?0.5 Ma, respectively). Tonaliteporphyry, the progenitor of porphyry copper mineralization inthe complex, represents a significantly younger intrusive eventat 24 Ma. Relatively calcic (An_95—50) plagioclase coresand salite to augite composition clinopyroxene are texturallyearly phases in the intrusive rocks. The main mafic mineral,calcic amphibole, generally has corroded clinopyroxene coresand may, like biotite, K-feldspar and quartz, generally be alate-stage, not a primary liquidus phase. Petrographic featuresindicate that the mafic minerals in the plutonic rocks crystallizedfrom melt, rather than being restite phases. The intrusive rocks cover an extensive silica range (45–75wt. per cent), do not exhibit simple straight-line variationon Harker diagrams for many elements (e.g. TiO₂, FeO, P₂O₅ andSr), and most are relatively depleted in incompatible traceelements (Rb, Zr, and REE). Major and trace element modellingsupports derivation of the complex by shallow level fractionalcrystallization dominated by removal of the phases calcic plagioclase,clinopyroxene, and magnetite from a parental magma closely resemblingrecent basaltic rocks in New Britain. The fact that the plutonicrocks are almost chemically indistinguishable from late Cainozoiccalc-alkaline volcanic rocks of New Britain supports fractionalcrystallization as a viable mechanism for generating these island-arcvolcanic rocks and indicates an analogous origin for the initialmagma. Granites, such as those of the Uasilau-Yau Yau intrusive complex,which are probably generated by partial melting of subductedoceanic crust or the overlying mantle, may be termed mantleor M-type granites. Documentation of the characteristics ofM-type versus normal I-type granites may enable the recognitionof M-type plutonic rocks in older, possibly more deeply erodedgeologic terrains. This would, by analogy to their volcanicequivalents, be very helpful in tectonic interpretations. Also,such plutonic rocks have known potential for Cu-Au mineralization.  相似文献   

TESTING LAKE SEDIMENT AND DENDROGEOMORPHIC PROXIES FOR LITTLE ICE AGE ENVIRONMENTAL CHANGE IN THE UPPER FRASER RIVER AREA,BRITISH COLUMBIA,CANADA     

RANDY W. DIRSZOWSKY  JOSEPH R. DESLOGES 《Geografiska Annaler: Series A, Physical Geography》2010,92(3):393-410

This study assesses Little Ice Age (LIA) lake sediment morphological and geochemical records and moraine chronologies in the upper Fraser River watershed, British Columbia, Canada, to resolve differences in paleoenvironmental interpretation and to clarify sediment production and sediment delivery processes within alpine geomorphic systems. Moose Lake (13.9 km²), situated at 1032 m a.s.l., contains a partially varved record indicating variable rates of accumulation during the last millennium that, in general, coincide with previously documented LIA glacial advances in the region and locally. Dendrochronological assessment of forefield surfaces in the headwaters of the catchment (Reef Icefield) shows that periods of moraine construction occurred just prior to ad 1770, ad 1839 and ad 1883, and some time before ad 1570. Taken collectively, increases in varve thickness within eight Moose Lake sediment cores coincide with documented glacier advances over the twelfth through fourteenth centuries, the eighteenth century, and nineteenth through twentieth centuries. Glacial activity during the sixteenth century is also indicated. While varve thickness variations in proximal and distal sediments clearly reflect glacial activity upstream of Moose Lake, the intermediate varve record is relatively insensitive to these decadal and longer‐term catchment processes. Variations in Ca and related elements derived from glaciated carbonate terrain within the Moose River sub‐catchment (including Reef Icefield) indicate gradually increasing delivery from these sources from the twelfth through twentieth centuries even where the varve thickness record is unresponsive. Elevated carbonate concentrations confirm glacial activity c. ad 1200, ad 1500, ad 1750, and ad 1900.  相似文献   

The influence of interior gradients of potential vorticity on rapid cyclogenesis     

JOSEPH A. ZEHNDER  DANIEL KEYSER 《地球，A辑:动力气象学与海洋学》1991,43(3):198-212

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