Climatic Warming in the Spanish Mediterranean: Natural Trend or Urban Effect     

J. Quereda Sala  A. Gil Olcina  A. Perez Cuevas  J. Olcina Cantos  A. Rico Amoros  E. Montón Chiva 《Climatic change》2000,46(4):473-483

The evolution of the mean annual temperatures recordedin the major historical network of SpanishMediterranean observatories(36°N–45°/60°W–4°E)exhibits a significant warming trend. Analysis of thetrend is difficult and could be biased by non-climaticprocesses such as the urban effect and weather stationrelocation, which also need to be taken intoaccount.The present work examines the effects of non-climaticprocesses and shows that most of the temperature risecould be due to an urban effect. On correcting for theurban effect, the actual rise was found to be zero ornegligible. The assumption of temperature stability inthe Spanish Mediterranean should thereforenot be rejected.  相似文献   

The population of the Polish countryside: Demography and living conditions     

Bronislaw Górz  Wlodzimierz Kurek 《GeoJournal》2000,50(2-3):101-104

Despite substantial rural-urban migration, 38.1 percent of the population of Poland still live in the countryside and the total numbers are only 0.9mln fewer than in 1946. At present the rural population is increasing and the rate of natural increase (though falling) is higher than in the towns though the productive age group is smaller. However, these human resources are not being properly used and the results can be seen in terms of economic inefficiency, low living standards and a high level of state support. Loss of jobs in factories and state farms results in welfare payments by the state and considerable 'hidden unemployment' on small family farms where profitability is constrained by inefficient use of labour. Poverty among the rural population is evident through a collapse of house building and considerable domestic overcrowding. However, conditions vary considerably across the country and this must be reflected in the economic and social policies drawn up for the new administrative regions introduced in 1999. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Magnitude-Intensity Relationships in the Ibero-Magrebhian Region     

C. López Casado  S. Molina  J. J. Giner  J. Delgado 《Natural Hazards》2000,22(3):269-294

In this paper we present magnitude (Ms) – magnitude(mb) and magnitude-intensity relationships which areconsidered the most adequate in the Ibero-Maghrebianregion. This work is based on selected samples ofrecently revised events with magnitude mb assigned bythe Instituto Geográfico Nacional (I.G.N.) and Msassigned by I.S.C and N.E.I.C., and isoseismal mapsfrom 142 events. Using these data, we have obtainedone magnitude (Ms) – magnitude (mb) relationship, twomagnitude (mb and Ms) assignment relationships viaepicentral intensity (I₀), and ten magnitude (mb andMs) assignments relationships via macroseismicinformation: four using Ambraseys' methodology (1985)and six using the isoseismal area of degree III, IV and VI.According to the obtained results it could be concluded that historical magnitude assignment with lesser uncertainties are those obtained via macroseismic information using magnitude-intensity relationships with Ambraseys' methodology (1985). The magnitude-isoseismal area assignment relationships have, in most cases, great differences depending on the degree of the isoseismal area used. Magnitude assignments via epicentral intensity have the highest uncertainties. Geographic regionalization of the relationshipshas been studied but the highest correlations and statistical significance are obtained when we fit all the Ibero-Maghrebian region data.Finally we have used the results obtained in this workto assign magnitude to some important historicalearthquakes in the Ibero-Maghrebian region: the 1755Lisbon earthquake, the 1680 Málaga earthquake, the1829 Torrevieja earthquake and the 1884 Arenas del Reyearthquake. According to our relationships andmethodology we have assigned an Ms value of 9.3 ±0.6 to the 1755 Lisbon earthquake (its mb magnitudecannot be estimated due to the saturation of the mbscale), an mb value of 6.3 ±0.4 and an Ms valueof 6.9 ± 0.6 to the 1829 Torrevieja earthquake, anmb value of 6.2 ± 0.4 and an Ms value of 6.4 ±0.6 to the 1680 Málaga earthquake and an mb valueof 6.1 ± 0.4 and an Ms value of 6.5 ± 0.6 tothe 1884 Arenas del Rey earthquake.  相似文献   

Do diatoms in the Swiss Alps reflect the length of ice-cover?   总被引：11，自引：0，他引：11  

André F. Lotter  Christian Bigler 《Aquatic Sciences - Research Across Boundaries》2000,62(2):125-141

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Quiet-time periods observed by EPHIN/SOHO during the minimum of the 22nd solar cycle     

Gómez-Herrero  Raúl  RodrÍguez-FrÍas  M. Dolores  del Peral  Luis  Sequeiros  Juan  Müller-Mellin  Reinhold  Kunow  Horst  Sierks  Holger 《Solar physics》2000,194(2):405-413

An analysis of the hydrogen and helium isotopic composition from EPHIN data, during the quiet-time period from January 1 to June 1, 1996, is presented. An isotopic discrimination and background rejection have been applied and relationships between the abundances of ²H/¹H, ³He/⁴He, and ⁴He/¹H have been calculated. The energy spectra in the 4–50 MeV nucl^–1 range have been obtained and the contribution of the different spectral components have been analysed in this energy range. We conclude that the main contribution to the ⁴He spectrum is of anomalous origin, while the proton and ³He spectra have contributions mainly from particles of solar origin at low energies and from the galactic cosmic radiation modulated by the heliosphere at high energies. The deuterium spectrum is mainly of galactic origin.  相似文献   

Tectonics of an extinct ridge-transform intersection,Drake Passage (Antarctica)     

Maldonado  Andrés  Carlos Balanyá  Juan  Barnolas  Antonio  Galindo-Zaldívar  Jesús  Hernández  Javier  Jabaloy  Antonio  Livermore  Roy  Miguel Martínez-Martínez  José  Rodríguez-Fernández  José  Sanz de Galdeano  Carlos  Somoza  Luis  Suriñach  Emma  Viseras  César 《Marine Geophysical Researches》2000,21(1-2):43-68

New swath bathymetric, multichannel seismic and magnetic data reveal the complexity of the intersection between the extinct West Scotia Ridge (WSR) and the Shackleton Fracture Zone (SFZ), a first-order NW-SE trending high-relief ridge cutting across the Drake Passage. The SFZ is composed of shallow, ridge segments and depressions, largely parallel to the fracture zone with an `en echelon' pattern in plan view. These features are bounded by tectonic lineaments, interpreted as faults. The axial valley of the spreading center intersects the fracture zone in a complex area of deformation, where N120° E lineaments and E–W faults anastomose on both sides of the intersection. The fracture zone developed within an extensional regime, which facilitated the formation of oceanic transverse ridges parallel to the fracture zone and depressions attributed to pull-apart basins, bounded by normal and strike-slip faults.On the multichannel seismic (MCS) profiles, the igneous crust is well stratified, with numerous discontinuous high-amplitude reflectors and many irregular diffractions at the top, and a thicker layer below. The latter has sparse and weak reflectors, although it locally contains strong, dipping reflections. A bright, slightly undulating reflector observed below the spreading center axial valley at about 0.75 s (twt) depth in the igneous crust is interpreted as an indication of the relict axial magma chamber. Deep, high-amplitude subhorizontal and slightly dipping reflections are observed between 1.8 and 3.2 s (twt) below sea floor, but are preferentially located at about 2.8–3.0 s (twt) depth. Where these reflections are more continuous they may represent the Mohorovicic seismic discontinuity. More locally, short (2–3 km long), very high-amplitude reflections observed at 3.6 and 4.3 s (twt) depth below sea floor are attributed to an interlayered upper mantle transition zone. The MCS profiles also show a pattern of regularly spaced, steep-inclined reflectors, which cut across layers 2 and 3 of the oceanic crust. These reflectors are attributed to deformation under a transpressional regime that developed along the SFZ, shortly after spreading ceased at the WSR. Magnetic anomalies 5 to 5 E may be confidently identified on the flanks of the WSR. Our spreading model assumes slow rates (ca. 10–20 mm/yr), with slight asymmetries favoring the southeastern flank between 5C and 5, and the northwestern flank between 5 and extinction. The spreading rate asymmetry means that accretion was slower during formation of the steeper, shallower, southeastern flank than of the northwestern flank.  相似文献   

Characteristics of Astronomy-Related Organizations     

André Heck 《Astrophysics and Space Science》2000,274(4):733-783

Geographical distributions, ages and sizes of astronomy-relatedorganizations have been investigated from comprehensive and up-to-datesamples extracted from the master files for StarGuides/StarWorlds.Results for professional institutions, associations, planetariums, andpublic observatories are commented, as well as specific distributions forastronomy-related publishers and commercial-software producers.The highly uneven general pattern displayed by geographical distributionsis still very much the same as it was at the beginning of the XXthcentury, even if the densities are higher – another illustration of thewell-known socio-economic effect of self-reinforcement. Othergeographical peculiarities (local concentrations, national cultures andpolicies, electronic astronomy,...) are discussed in the paper, aswell as the uneasy separation between amateur and professional astronomersin associations.Some events had a clear impact on the rate of foundation ofastronomy-related organizations, such as World Wars I and II, thebeginning of space exploration, the landing of man on the Moon, the end ofthe Cold War, spectacular comets, and so on. However, as detailed in thepaper, not all of them affected in the same way Western Europe and NorthAmerica, nor the various types of organizations.The size of the vast majority of astronomy-related organizations isrelatively small, with again some differences between Western Europe andNorth America.  相似文献   

A Search for Warm Neutral Gas Associated with the Giant HII Region NGC 604     

A.I. Gómez de Castro  L. Sanz  J. Beckman 《Astrophysics and Space Science》2000,272(1-3):15-22

The characteristics of the halo gas and its interaction with the galactic disk in spiral galaxies are poorly known; this is particularly true for the warm neutral gas associated with HVCs and galactic chimneys. The detection of absorption features such as the NaI D or the CaII (H,K)lines is instrumental to study its detailed physical properties but requires very long integration times. In this work very deep optical spectra of NGC 604, the brightest giant HII region among the nearby spirals, are presented. The detection of two absorption components at LSR velocities -255 km/s and −20 km/s respectively, is reported; the first component is associated with the HII region. The inferred line width after deconvolution is 155 km/s; this large width is produced by the blending of the multiple absorption components produced by the diverse sources of internal motion (expanding shells and general turbulence). The radial velocity of the CaII absorption is slightly larger than the measured in the HII emission lines suggesting a possible flow of gas into the halo above the young star cluster. The large ratio x = W _λ (NaID_2)/W _λ (CaIIK) = 0.7indicates the probable presence of shocks which release Ca from the dust grains into the gas phase. The lower velocity component most likely trace galactic gas. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Fragmentation, transport and deposition of a low-grade ignimbrite: The Citlaltépetl Ignimbrite, Eastern México     

Arturo Gómez-Tuena  Gerardo Carrasco-Núñez 《Bulletin of Volcanology》1999,60(6):448-464

 The Citlaltépetl Ignimbrite records one of the largest explosive events during the Holocene activity of Citlaltépetl Volcano (Pico de Orizaba). Multiple pyroclastic flow units, a fall deposit, and some lahar units were emplaced between 8500–9000 y B.P. as a result of repetitive but discrete explosive events. The whole ignimbrite resulted from discrete fluctuations in eruptive intensity that decreased with time. The initial pyroclastic flow pulse was by far the most violent and widespread event, and its deposits show conspicuous variations in structure and texture that could be associated with different mechanisms of transport and emplacement. Subpopulation Sequential Fragmentation Transport (SFT) analyses were carried out in order to determine the physical mechanisms that selectively concentrate or remove particles in the moving flows. We suggest that lateral and temporal changes in the flow rheology, in which fluidization, yield strength, entrainment of atmospheric air, and sedimentation played a dominant role in flow propagation and emplacement, may imprint a unique signature in the grain-size spectra. The lowermost unit of the Citlaltépetl Ignimbrite can be envisaged by a model in which progressive aggradation near the vent became replaced by en masse emplacement farther outward. Received: 24 March 1998 / Accepted: 9 October 1998  相似文献   

Groundwater as a geologic agent: An overview of the causes, processes, and manifestations   总被引：29，自引：4，他引：25  

József Tóth 《Hydrogeology Journal》1999,7(1):1-14

 The objective of the present paper is to show that groundwater is a general geologic agent. This perception could not, and did not, evolve until the system nature of basinal groundwater flow and its properties, geometries, and controlling factors became recognized and understood through the 1960s and 1970s. The two fundamental causes for groundwater's active role in nature are its ability to interact with the ambient environment and the systematized spatial distribution of its flow. Interaction and flow occur simultaneously at all scales of space and time, although at correspondingly varying rates and intensities. Thus, effects of groundwater flow are created from the land surface to the greatest depths of the porous parts of the Earth's crust, and from a day's length through geologic times. Three main types of interaction between groundwater and environment are identified in this paper, with several special processes for each one, namely: (1) Chemical interaction, with processes of dissolution, hydration, hydrolysis, oxidation-reduction, attack by acids, chemical precipitation, base exchange, sulfate reduction, concentration, and ultrafiltration or osmosis; (2) Physical interaction, with processes of lubrication and pore-pressure modification; and (3) Kinetic interaction, with the transport processes of water, aqueous and nonaqueous matter, and heat. Owing to the transporting ability and spatial patterns of basinal flow, the effects of interaction are cumulative and distributed according to the geometries of the flow systems. The number and diversity of natural phenomena that are generated by groundwater flow are almost unlimited, due to the fact that the relatively few basic types are modified by some or all of the three components of the hydrogeologic environment: topography, geology, and climate. The six basic groups into which manifestations of groundwater flow have been divided are: (1) Hydrology and hydraulics; (2) Chemistry and mineralogy; (3) Vegetation; (4) Soil and rock mechanics; (5) Geomorphology; and (6) Transport and accumulation. Based on such a diversity of effects and manifestations, it is concluded that groundwater is a general geologic agent. Received, December 1998 · Revised, January 1999 · Accepted, January 1999  相似文献