CHANGES IN THE MORPHOLOGY OF THREE AMERICAN CENTRAL BUSINESS DISTRICTS 1952–1966     

David C. Weaver 《The Professional geographer》1969,21(6):406-410

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A calculation of the large scale three dimensional distribution of diabatic heating in the atmosphere     

David Drew Houghton 《Meteorology and Atmospheric Physics》1962,12(4):407-425

Summary The large scale three-dimensional diabatic heating in the atmosphere is computed at 12 isentropic surfaces for a particular twelve hour time period. Using a method due toErtel, the continuity equation is combined with the equations of motion to give an explicit relation between diabatic heating and changes in potential vorticity and stability along isentropic surface trajectories. The results are barely of useful accuracy and reliability and this only under favorable conditions. The distribution of diabatic heating is qualitatively reasonable in the regions near the tropopause, close to the ground, above a cloud or moist layer, and within an area of general condensation. Errors and approximations make the computed values completely unreliable in areas of large anticyclonic vorticity or large baroclinity. Comparison of magnitudes with those computed from rainfall observations and with those measured directly at the earth's surface shows agreement in sign and within a factor of three in the areas of best data. The results emphasize that there are regions and periods where diabatic heating in the free atmosphere may be important in controlling atmospheric behavior. Sample calculations in one of these regions using values of diabatic heating computed by this study illustrate that this process is of comparable importance with the adiabatic process in determining vertical velocity.

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Zusammenfassung Die großräumige nichtadiabatische Erwärmung der Atmosphäre in 12 isentropen Flächen während eines 12stündigen Zeitabschnittes wird berechnet. Unter Verwendung einer Methode vonErtel liefert eine Kombination der Kontinuitätsgleichung mit den Bewegungsgleichungen eine explizite Beziehung zwischen der nichtadiabatischen Erwärmung, der potentiellen Vorticity und der Stabilität entlang der isentropen Trajektorien. Das Resultat ist von beschränkter Genauigkeit — und auch dies nur unter günstigen Bedingungen. Qualitativ brauchbare Verteilungen der nichtadiabatischen Erwärmung erhält man nahe der Tropopause, in Bodennähe, über einer Schicht von Wolken oder feuchter Luft und innerhalb der Zonen mit verbreiteter Kondensation. In Gebieten mit großer antizyklonaler Vorticity oder großer Baroklinität werden die berechneten Werte infolge von Meß- und Approximationsfehlern völlig ungenau. In den Gebieten mit optimalen Voraussetzungen stimmen die berechneten Werte mit den aus Niederschlagsmessungen abgeleiteten oder am Boden direkt beobachteten im Vorzeichen und innerhalb eines Faktors von 3 überein. Die Ergebnisse der vorliegenden Untersuchung weisen erneut darauf hin, daß in manchen Gebieten bzw. Zeitabschnitten das Verhalten der freien Atmosphäre durch nichtadiabatische Erwärmung wesentlich beeinflußt sein kann. Stichprobenweise Berechnungen für eines dieser Gebiete zeigen, daß die theoretisch ermittelte nichtadiabatische Erwärmung für die resultierende Vertikalgeschwindigkeit der Luft quantitativ von ähnlicher Bedeutung ist wie der adiabatische Prozeß.

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Résumé L'auteur a calculé le réchauffement non adiabatique, à grande échelle, de l'atmosphère à 12 niveaux isentropes pendant un intervalle de 12 heures. Une méthode établie parErtel combine l'équation de continuité et les équations de mouvement et aboutit à une relation explicite entre le réchauffement non adiabatique, la vorticity potentielle et la stabilité le long de trajectoires isentropes. Le résultat n'a qu'une exactitude approchée, et cela dans des conditions favorables seulement. On obtient une répartition utilisable du réchauffement non adiabatique au voisinage de la tropopause, du sol, au-dessus d'une couche de nuages ou d'air humide, ainsi qu'à l'intérieur des zones à forte condensation. Dans les régions à grande vorticity anticyclonique et à grande baroclinité, les valeurs calculées deviennent tout à fait inexactes par suite d'une approximation insuffisante et d'erreurs de mesure. Dans les régions à conditions favorables par contre, les valeurs calculées correspondent à celles que l'on peut tirer de la mesure des précipitations ou de celles que l'on mesure au sol, cela au signe et à un facteur 3 près. Le résultat de cette étude montre à nouveau que dans certaines régions ou certains laps de temps l'état de l'atmosphère peut être notablement conditionné par un réchauffement non adiabatique. Des épreuves faites pour l'une de ces régions montrent que le réchauffement non adiabatique obtenu par calcul est quantitativement aussi important pour la vitesse verticale résultante de l'air que le processus adiabatique.

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With 7 Figures  相似文献   

Modification of an acoustic pinger to transmit temperature data     

Grant Blackinton  David Epp 《Marine Geophysical Researches》1978,3(4):407-411

An acoustic pinger can be modified to transmit two pings per second with the delay time between pings controlled by the temperature of an external thermistor. The precision of the temperature measurements is on the order of 0.1°C. This modification does not interfere with the normal depth indicating function of the pinger and is an inexpensive means of obtaining water temperature data.  相似文献   

Comparison of oscillatory and stationary flow through porous media     

Kevin R. Hall  Greg M. Smith  David J. Turcke 《Coastal Engineering》1995,24(3-4)

Experiments were conducted in an oscillatory water tunnel to investigate what effects temporal inertia has on the resistance of a granular medium. The flow law governing stationary porous media flow is reasonably well accepted and understood but the effects of unsteady flow have commonly been neglected. The present research was designed to assess the magnitude of the acceleration effects on media of uniformly packed spheres of equal diameter and on one sample of randomly placed stone.Oscillatory flow tests were made in a large oscillatory flume tunnel with periods varying from 3 to 12 seconds. The influence of properties of the medium (grain size and porosity) were tested by using spheres with two different diameters and packing each size sphere in different geometric arrangements. Tests made on a stone sample provided a qualitative assessment of the effects of more random material properties.For the experiments described in this paper, the Forchheimer unsteady-stationary flow law described the oscillatory measurements well when velocities and energy losses were maximum. Empirical coefficients determined from steady-stationary flow were generally found to apply to the unsteady flow, however some evidence of dependency on the period of oscillation was noted.  相似文献   

North Atlantic fisheries: Trends, status and management issues     

David Symes 《Ocean & Coastal Management》1997,35(2-3)

Despite the fact that the North Atlantic remains one of the most productive of oceanic regions, its importance has declined both relatively and absolutely. A key factor has been the steady erosion of stocks of some of the major food fish species, including the ubiquitous cod. The paper traces the main trends in catches since 1973 and outlines the development of fisheries management in the region from the formation of ICES in 1902, through the creation of coastal state management in the 1970s to the UN Agreement on high-seas fishing in 1995. Finally, the key issues for fisheries management are identified, and the invited papers are contextualised.  相似文献   

Effects on zooplankton of a warmer ocean: Recent evidence from the Northeast Pacific     

David L. Mackas  Sonia Batten 《Progress in Oceanography》2007,75(2):223-252

The consequences for pelagic communities of warming trends in mid and high latitude ocean regions could be substantial, but their magnitude and trajectory are not yet known. Environmental changes predicted by climate models (and beginning to be confirmed by observations) include warming and freshening of the upper ocean and reduction in the extent and duration of ice cover. One way to evaluate response scenarios is by comparing how “similar” zooplankton communities have differed among years and/or locations with differing temperature. The subarctic Pacific is a strong candidate for such comparisons, because the same mix of zooplankton species dominates over a wide range of temperature climatologies, and observations have spanned substantial temperature variability at interannual-to-decadal time scales. In this paper, we review and extend copepod abundance and phenology time series from net tow and Continuous Plankton Recorder surveys in the subarctic Northeast Pacific. The two strongest responses we have observed are latitudinal shifts in centers of abundance of many species (poleward under warm conditions), and changes in the life cycle timing of Neocalanus plumchrus in both oceanic and coastal regions (earlier by several weeks in warm years and at warmer locations). These zooplankton data, plus indices of higher trophic level responses such as reproduction, growth and survival of pelagic fish and seabirds, are all moderately-to-strongly intercorrelated (∣r∣ = 0.25-0.8) with indices of local and basin-scale temperature anomalies. A principal components analysis of the normalized anomaly time series from 1979 to 2004 shows that a single “warm-and-low-productivity” vs. “cool-and-high-productivity” component axis accounts for over half of the variance/covariance. Prior to 1990, the scores for this component were negative (“cool” and “productive”) or near zero except positive in the El Niño years 1983 and 1987. The scores were strongly and increasingly positive (“warm” and “low productivity”) from 1992 to 1998; negative from 1999 to 2002; and again increasingly positive from 2003-present. We suggest that, in strongly seasonal environments, anomalously high temperature may provide misleading environmental cues that contribute to timing mismatch between life history events and the more-nearly-fixed seasonality of insolation, stratification, and food supply.  相似文献   

Analysis of medaka cytochrome P450 3A homotropic and heterotropic cooperativity     

Kullman SW  Kashiwada S  Hinton DE 《Marine environmental research》2004,58(2-5):469-473

We have previously demonstrated that medaka CYP3A is associated with metabolism of several endobiotics including steroids and bile acids. In this study, we demonstrate that medaka CYP3A catalysis exhibits unusual kinetic behaviors consistent with allosteric interaction which cannot be described by hyperbolic kinetic models. Using 7-benzyloxy-4-(trifluoromethyl)-coumarin (BFC) and nonylphenol as CYP3A substrates, we describe both homotropic and heterotropic cooperative interactions. Given the role of CYP3A in maintaining the homeostatic balance for numerous endobiotics, enzymatic activation/inhibition by endocrine disruptors (EDCs) represents a putative (non-genomic) mechanism for endocrine disruption.  相似文献   

Imaging of Buried Archaeological Materials: The Reflection Properties of Archaeological Wood   总被引：1，自引：0，他引：1  

Stephanie H.L. Arnott  Justin K. Dix  Angus I. Best  David J. Gregory 《Marine Geophysical Researches》2005,26(2-4):135-144

Effective marine archaeological site management demands detailed information on not only the spatial distribution of artefacts but also the degradation state of the materials present. Although sonar methods have frequently been used in an attempt to detect buried wooden shipwrecks they are currently unable to indicate their degradation state. To assess the sensitivity of acoustic measurements to changes in the degradation state of such material, and hence the potential for sonars to quantify degradation, laboratory measurements of compressional wave velocity, as well as bulk density for oak and pine samples, in varying states of decay, were undertaken. These data enabled the calculation of theoretical reflection coefficients for such materials buried in various marine sediments. As wood degrades, the reflection coefficients become more negative, resulting in the hypothesis that the more degraded wood becomes, the easier it should be to detect. Typical reflection coefficients of the order of −0.43 and −0.52 for the most degraded oak and pine samples in sand are predicted. Conversely, for wood exposed to seawater the predicted reflection coefficients are large and positive for undegraded material (0.35 for oak, 0.18 for pine) and decrease to zero or slightly below for the most degraded samples. This indicates that exposed timbers, when heavily degraded, can be acoustically transparent and so undetectable by acoustic methods. Corroboration of these experimental results was provided through comparison with high resolution seismic reflection data that has been acquired over two shipwrecks.  相似文献   

An improved multiple-frequency method for measuring in situ target strengths     

Conti  Stephane G.; Demer  David A.; Soule  Michael A.; Conti  Jean H.E. 《ICES Journal of Marine Science》2005,62(8):1636-1646

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Multi-decadal synthesis of benthic–pelagic coupling in the western arctic: Role of cross-shelf advective processes     

Kenneth H. Dunton  Jonathan L. Goodall  Susan V. Schonberg  Jacqueline M. Grebmeier  David R. Maidment 《Deep Sea Research Part II: Topical Studies in Oceanography》2005,52(24-26):3462

Using geographic information systems (GIS) software and geostatistical techniques, we utilized three decades of water-column chlorophyll a data to examine the relative importance of autochthonous versus allochthonous sources of reduced carbon to benthic communities that occur from the northern Bering to the eastern Beaufort Sea shelf. Spatial trend analyses revealed areas of high benthic biomass (>300 g m⁻²) and chlorophyll (>150 mg m⁻²) on both the southern and northern Chukchi shelf; both areas are known as depositional centers for reduced organic matter that originates on the Bering Sea shelf and is advected northward in Anadyr and Bering shelf water masses. We found a significant correlation between biomass and chlorophyll a in the Chukchi Sea, reflective of the strong benthic–pelagic coupling in a system that is utilized heavily by benthic-feeding marine mammals. In contrast, there was no significant correlation between biomass and chlorophyll in the Beaufort Sea, which by comparison, is considerably less productive (biomass and chlorophyll, <75 g m⁻² and <50 mg m⁻², respectively). One notable exception is an area of relatively high biomass (50–100 g m⁻²) and chlorophyll (80 mg m⁻²) near Barter Island in the eastern Beaufort Sea. Compared to other adjacent areas in the Beaufort Sea, the chlorophyll values in the vicinity of Barter Island were considerably higher and likely reflect a long-hypothesized upwelling in that area and close coupling between the benthos and autochthonous production. In the Bering Sea, a drop in benthic biomass in 1994 compared with previous measurements (1974–1993) may support earlier observations that document a decline in biomass that began between the 1980s and 1990s in the Chirikov Basin and south of St. Lawrence Island. The results of this study indicate that the benthos is an excellent long-term indicator of both local and physical advective processes. In addition, this work provides further evidence that secondary production on arctic shelves can be significantly augmented by reduced carbon advected from highly productive adjacent shelves.  相似文献