Fisheries in upwelling regions — with special reference to peruvian waters     

Garth I. Murphy 《Geoforum》1972,3(3):63-71

The anchovy population that is the basis of the Peru fishery, the world's largest, is a phytoplankton feeding species, supported by an upwelling based ecosystem. The fish is very short-lived and grows rapidly — both criteria for high turnover rate — high yield fisheries. The maximum sustainable yield is around 10 million metric tons. Analysis of the dynamics of the fishery suggests that the fleet is overbuilt, applying too much fishing effort, and slightly overfishing the population. In consequence, the population may be approaching a size and stress level at which it will be unstable.  相似文献   

Comparison of photo-electric nuclei counters     

L. W. Pollak  T. Murphy 《Pure and Applied Geophysics》1953,25(1):44-60

Summary Three identical photo-electric nuclei counters have been compared in pairs using natural and artificially produced aerosols. The main results of comparisons were obtained in the laboratory under controlled conditions using nuclei stored in a gasometer, consisting of a radiosonde balloon inflated to a volume of 4000 litres. Because of its large size, it enables the constants in the decay law of condensation nuclei to be determined with greater accuracy than heretofore. The gasometer is more convenient, more easily stored after use and its cost is a very small fraction of that of a metal one. No effects detrimental to the stored gas or any other objection to its use have been found.The results of several thousand comparisons show that no two counters will record the same concentration of nuclei in samples taken simultaneously from the same enclosure. Each counter shows small random fluctuations of short period, ±3% of the concentration, with superimposed unpredictable variations of longer period. The differences in readings between any two counters depend on the concentration, the type and the relative amounts of the charged and uncharged nuclei in a sample. These differences, which seldom exceed ±20% of the concentration, are rather constant for several hours and even days. This feature enables allowances to be made for the differences and a routine of observations is suggested which has been successfully employed in the laboratory and in the open.Each counter exhibits, when operated continuously, a drift which consists of a tendency to indicate that the concentration of nuclei increases when a constant value or a slight decrease is expected theoretically.A study of the statistical analysis of the individual readings and a detailed investigation of the components of each counter have not lead to an elucidation and elimination of the differences between counters. The investigation of the differences is still proceeding.

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Zusammenfassung Drei identische photo-elektrische Kernzähler wurden paarweise mittels natürlicher und künstlich erzeugter Aerosole verglichen. Die Hauptresultate der Vergleichungen wurden im Laboratorium unter kontrollierten Bedingungen mit Hilfe von Kondensations-Kernen erhalten, welche in einem grossen Gasometer gespeichert worden waren. Dieser Gasometer besteht aus einen Radiosonde-Ballon, der auf ein Volumen von 4000 Litern aufgeblasen wurde. Wegen seiner Grösse ermöglicht er die Bestimmung der Konstanten des Abklingungs-Gesetzes der Kernkonzentration mit grösserer Genauigkeit als es bisher möglich war. Der neue Gasometer ist bequemer, kann, wenn nicht benötigt, leicht weggeräumt und aufbewahrt werden und kostet nur einen kleinen Bruchteil eines aus Metal hergestellten Gasbehälters. Es wurde kein schädlicher Einfluss der Gummihülle auf das gespeicherte Gas festgestellt und auf Grund unserer Beobachtungen besteht kein Einwand gegen die Benützung eines Gummigasometers.Die Resultate von mehreren tausend Vergleichungen lehren, dass keine zwei photoelektrischen Kernzähler die genau gleiche Konzentration der Kerne in Proben, welche gleichzeitig demselben Behälter entnommen werden, angeben. Jeder Kernzähler zeigt kurzperiodische, zufällige Schwankungen von ±3% der Konzentration, welche von nicht vorauszusagenden Variationen längerer Periode überlagert sind. Die Differenzen in den Lesungen irgend zweier photo-elektrischer Kernzähler hängen von der Konzentration der Kerne, ihrem Charakter und dem Verhältnis der Anzahl der geladenen und ungeladenen Kerne in der Probe ab. Diese Differenzen, welche selten ±20% der Konzentration übersteigen, sind während mehrerer Stunden und sogar Tage ziemlich konstant. Diese Eigenschaft ermöglicht es, die Differenzen in Rechnung zu ziehen und ein Beobachtungs-Schema vorzuschlagen, welches sowohl im Laboratorium als auch im Freien mit Erfolg angewendet wurde.Jeder photo-elektrische Kernzähler zeigte, wenn er ununterbrochen benützt wurde, einen Drift, der darin besteht, dass der Zähler eine kleine, mehr oder weniger stetige Zunahme in der Konzentration der Kerne vortäuscht, wenn konstante Kernzahl oder eine geringe Abnahme derselben theoretisch erwartet wird.Die statistische Analyse der Einzelmessungen und eine eingehende Untersuchung der Bestandteile jedes einzelnen photo-elektrischen Kernzählers hat zu keiner Aufklärung und Beseitigung der Differenzen der Kernzähler geführt. Die Untersuchung der Differenzen wird fortgesetzt.

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The post-eclipse brightening of Io     

D.P. Cruikshank  Robert E. Murphy 《Icarus》1973,20(1):7-17

We review the photometric work on eclipse reappearances of Io. New observations of eclipse reappearances of Io confirm the post-eclipse brightness anomaly reported by Binder and Cruikshank (1964) but testify to its intermittent nature. A post-eclipse anomaly of approximately 0.07 mag was observed on two occasions in 1972, while observations of Europa and Ganymede showed no brightness anomaly greater than 0.01 mag. The atmospheric condensation model for the anomaly on Io is reviewed in terms of the quantity of frost required to produce the effect and the corresponding amount of gas liberated to the atmosphere upon sublimation. The observational data and the results from a stellar occultation are in general accord with the theoretical predictions of the stability of heavy gases on Io, while both observational and theoretical criteria are satisfied by a tenuous atmosphere of a heavy gas such as methane or ammonia having a surface pressure ～10^?7 bar.  相似文献   

The Enso-Fire Dynamic in Insular Southeast Asia     

Douglas O. fuller  Kevin Murphy 《Climatic change》2006,74(4):435-455

We examined the spatiotemporal patterns of fire in insular Southeast Asia from July 1996 to December 2001 using a set of consistent, nighttime fire observations provided by the Along Track Scanning Radiometer (ATSR) sensor. Monthly ATSR fire counts were analyzed relative to georeferenced climatic and land-cover data from a variety of sources. We found that fires were strongly correlated with Southern Oscillation Index (SOI) (r = ?0.75) and Niño 3.4 index (r = 0.72) in forested land-cover types within the equatorial belt (5.5^°S–5.5^°N). Cross-correlation analysis revealed that detrended SOI was modestly correlated (r = 0.42) with detrended monthly fire count with a positive lag of four months. However, our analysis also revealed that fire counts reached their maximum 6 months before the absolute maximum of SOI. Annual sums of SOI (∑_SOI) and fire counts revealed linearity for ∑_SOI≤ 0. Overall, the results suggest that ENSO indices may have limited predictive utility at a monthly time scale, but that temporal aggregation and additional fire observations may enhance our capacity to forecast fires in different cover types based on ENSO data.  相似文献   

Frequency distributions of transient regional climate change from perturbed physics ensembles of general circulation model simulations   总被引：1，自引：2，他引：1  

G. R. Harris  D. M. H. Sexton  B. B. B. Booth  M. Collins  J. M. Murphy  M. J. Webb 《Climate Dynamics》2006,27(4):357-375

Large ensembles of coupled atmosphere–ocean general circulation model (AOGCM) simulations are required to explore modelling uncertainty and make probabilistic predictions of future transient climate change at regional scales. These are not yet computationally feasible so we have developed a technique to emulate the response of such an ensemble by scaling equilibrium patterns of climate change derived from much cheaper “slab” model ensembles in which the atmospheric component of an AOGCM is coupled to a mixed-layer ocean. Climate feedback parameters are diagnosed for each member of a slab model ensemble and used to drive an energy balance model (EBM) to predict the time-dependent response of global surface temperature expected for different combinations of uncertain AOGCM parameters affecting atmospheric, land and sea-ice processes. The EBM projections are then used to scale normalised patterns of change derived for each slab member, and hence emulate the response of the relevant atmospheric model version when coupled to a dynamic ocean, in response to a 1% per annum increase in CO₂. The emulated responses are validated by comparison with predictions from a 17 member ensemble of AOGCM simulations, constructed from variants of HadCM3 using the same parameter combinations as 17 members of the slab model ensemble. Cross-validation permits estimation of the spatial and temporal dependence of emulation error, and also allows estimation of a correction field to correct discrepancies between the scaled equilibrium patterns and the transient response, reducing the emulation error. Emulated transient responses and their associated errors are obtained from the slab ensemble for 129 pseudo-HadCM3 versions containing multiple atmospheric parameter perturbations. These are combined to produce regional frequency distributions for the transient response of annual surface temperature change and boreal winter precipitation change. The technique can be extended to any surface climate variable demonstrating a scaleable, approximately linear response to forcing.  相似文献   

Grounding the virtual: The material effects of electronic grocery shopping     

Andrew J. Murphy 《Geoforum》2007,38(5):941-953

This paper addresses the materiality of computer-mediated retailing. The paper uncovers the “hidden geography” of e-commerce, considering how the seemingly simple act of doorstep food delivery is explicated in urban form, and in transportation and communication infrastructures. The paper categorises electronic grocery shopping (EGS) enterprises into three types: “bricks and clicks”, “pure-play” and the “infomediary”, and examines how each type of operation has been materialised in the urban landscape, and the infrastructure upon which each draws. The paper then considers the strategies EGS operations have used to offset the “killer costs” of logistics for electronic commerce. The paper concludes by considering how electronic grocery shopping is embedded within broader trends in consumer behaviour, and how these trends are manifested in the materiality of urban life. The paper argues that online grocers are in the vanguard of ventures habituating customers to the remote ordering and delayed delivery of products to the home. Through controlling this “last mile”, online retailers hope to extend the product offer to higher-margin and more problematic products, which are in themselves unprofitable to distribute direct to the customer, but which can be profitably combined with a grocery shop.  相似文献   

Roessingh, Martijn A. Ethnonationalism and Political Systems in Europe: A State of Tension     

Alexander B. Murphy 《GeoJournal》1998,44(1):91-92

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The C/CO ratio in B335 and the decaying dark matter neutrino hypothesis     

Murphy  Little  & Kelly 《Monthly notices of the Royal Astronomical Society》1998,294(4):635-641

C¹⁸O J  = 2–1, C¹⁷O J  = 2–1 and [C  I ] ³P₁–³P₀ emission from the dense cold cloud B335 has been observed and modelled in order to determine the C/CO ratio. The observed ratio is compared with a prediction by Tarafdar who assumes a mechanism in which the CO dissociation is caused by photons of energy ∼ 13.8 eV. These were postulated by Sciama to result from the decay of dark matter neutrinos. Our value for the C/CO ratio sets an upper limit to the strength of the neutrino decay dissociation process, thus providing a significant datum for interstellar chemistry theory.  相似文献   

Pivot poles and plate motion reconstructions     

T.H. Nelson  R.A. Baker  R.W. Murphy 《Tectonophysics》1981,74(1-2)

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An explosion seismology investigation of the continental margin west of the Hebrides, Scotland, at 58°N     

M.H.P. Bott  A.R. Armour  E.M. Himsworth  T. Murphy  G. Wylie 《Tectonophysics》1979,59(1-4)

During summer 1975, a line of large shots was fired across the continental margin between the Rockall Trough and the Hebridean shelf along 58°N. Arrivals were observed at temporary seismic stations set up across Scotland and in northwestern Ireland. A clear P₂ phase was observed to cross the margin and a converted phase P₁ also seen on the records is interpreted as travelling in the sub-sedimentary oceanic crust of Rockall Trough and in the upper continental crust beneath the shelf.The continental crust beneath the Hebridean shelf is estimated to be 27 ± 2 km thick, with P_g = 6.22 ± 0.03 km/s and P_n = 8.01 ± 0.04 km/s as determined by time-term analysis. P_g delays on the outer shelf are interpreted in terms of a seaward thickening wedge of Mesozoic sediments which pre-date the split. P_n beneath the Rockall Trough was poorly determined at 8.20 ± 0.17 km/s and the Moho is estimated to be 18 ± 2 km deep at 58°N. This and other seismic and gravity work indicates a northward thickening of the crust along the Rockall Trough, accounting for the northward decrease in the height of the slope.Our results, and those of gravity interpretations, indicate a relatively abrupt transition between continental and oceanic crust, possibly correlating with the lack of major shelf subsidence. This is attributed to a relatively cool origin for this margin. The main thinning of the continental crust beneath the slope is attributed to outslip of continental crustal material into and beneath the newly forming oceanic crust during the first few million years after the split, possibly enhanced by pre-split stretching.  相似文献