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61.
For a century or so, the Hong Kong Observatory (HKO) has been providing temperature forecast for the whole of Hong Kong with
the HKO Headquarters as the reference location. In recent decades, due to spreading of population from the main urban center
to satellite towns, there is an increasing demand for regional temperature forecasts. To support such provision, the HKO has
developed a regression model to provide objective guidance to forecasters in formulating forecasts of maximum and minimum
temperatures for the next day at various locations in Hong Kong. In this paper, the regression model is presented, together
with the assessment of its performance. Based on the verification of one year of forecasts, it is found that the root mean
square errors (RMSEs) of maximum (minimum) temperature forecasts are from about 1.3 to 2.1 (1.1 to 1.4) degrees, respectively.
The regression model is shown to have generally out-performed the operational regional spectral model then operated by HKO.
Regional temperature forecast methods of other meteorological or research centers are also surveyed. Equipped with the regression
model, the HKO has launched an online regional temperature forecast service for the next day in Hong Kong since March 2008. 相似文献
62.
The range of response frequencies for which spectral ordinates obtained from accelerograms may be considered reliable is limited by several factors, primary among them being the effects of filters that are routinely applied to remove noise from the records. Considerable attention has been focused on the low‐frequency limit of the usable spectral ordinates because of various engineering applications requiring long‐period spectral accelerations or displacements but only recently have rational approaches to selecting the high‐frequency limit been proposed. Since there are applications for which the high‐frequency spectral ordinates are important, the approaches to this issue presented in the recent studies are reviewed and their application to the ground‐motion database from Europe and the Middle East is explored. On the basis of the results of these analyses, it is concluded that a large proportion of this dataset can be used to provide reliable estimates of response spectral ordinates at much shorter periods than may have previously been considered feasible. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
63.
Maria C. Arango Fleur O. Strasser Julian J. Bommer Ruben Boroschek Diana Comte Hernando Tavera 《Journal of Seismology》2011,15(1):19-41
Earthquake hazard along the Peru–Chile subduction zone is amongst the highest in the world. The development of a database
of subduction-zone strong-motion recordings is, therefore, of great importance for ground-motion prediction in this region.
Accelerograms recorded by the different networks operators in Peru and Chile have been compiled and processed in a uniform
manner, and information on the source parameters of the causative earthquakes, fault-plane geometries and local site conditions
at the recording stations has been collected and reviewed to obtain high-quality metadata. The compiled database consists
of 98 triaxial ground-motion recordings from 15 subduction-type events with moment magnitudes ranging from 6.3 to 8.4, recorded
at 59 different sites in Peru and Chile, between 1966 and 2007. While the database presented in this study is not sufficient
for the derivation of a new predictive equation for ground motions from subduction events in the Peru–Chile region, it significantly
expands the global database of strong-motion data and associated metadata that can be used in the derivation of predictive
equations for subduction environments. Additionally, the compiled database will allow the assessment of existing predictive
models for subduction-type events in terms of their suitability for the Peru–Chile region, which directly influences seismic
hazard assessment in this region. 相似文献
64.
A New Genus and Species of Damsel-Dragonfly (Odonata: Isophlebioidea: Campterophlebiidae) in the Middle Jurassic of Inner Mongolia, China 总被引:1,自引:0,他引:1
The campterophlebiid new genus and species Ctenogampsophlebia reni is described from the Middle Jurassic of Inner Mongolia, China. It shows close similarities with the Lower to Middle Jurassic genera Gampsophlebia, and Petrophlebia, with closed and short subdiscoidal cells, confirming the attribution of these two other genera to the Campterophlebiidae. 相似文献
65.
66.
Staircases of gravelly river terrace deposits in southern England occupy valleys typically underlain by frost-susceptible and brecciated bedrocks. The valleys developed during the Quaternary by alternating episodes of (1) brecciation, incision and planation through the bedrock, forming wide low-relief erosion surfaces; and (2) aggradation in braidplains of gravel a few meters thick that bury the erosion surfaces. A conceptual model to account for some of the terraces proposes that brecciation resulted from ice segregation in the ice-rich layer in the upper meters of Pleistocene permafrost, making them vulnerable to fluvial thermal erosion and therefore predisposing the bedrock to planation. The low gradients of the valleys were adjusted such that rivers transferred fine materials out of the basins but lacked the competence to remove gravel, which therefore accumulated within floodplains. The model challenges the prevailing view of incision during climate transitions. It attributes incision and planation to very cold and arid permafrost conditions, when rivers had limited discharges and hillslopes supplied limited volumes of stony debris into valley bottoms. 相似文献
67.
Marc Antoine Couillard Gilbert Cabana Jean François Dery Gaétan Daigle Julian John Dodson 《Estuaries and Coasts》2011,34(6):1234-1245
Tomcod (Microgadus tomcod) in the St. Lawrence estuarine transition zone (ETZ) undergo an ontogenetic habitat shift. Older age classes, characterised
by a male-dominated sex ratio, disperse downstream over the summer months to occupy the colder more saline waters of the estuary.
Significant differences in length and mass along the salinity gradient were observed in September with upstream fish of any
given age class generally exhibiting greater growth. These differences were not seen in early summer. Benthic amphipod δ
34S signatures were strongly correlated with salinity and served to demonstrate that tomcod δ
34S signatures were not in isotopic equilibrium in the more saline waters of the ETZ. Seasonal distributional patterns, growth
dynamics and isotopic disequilibrium all indicate that the observed habitat shift may occur on an annual basis, following
winter aggregation in warmer, less saline waters. Tomcod located in the downstream parts of the ETZ, predominantly males,
were significantly more sexually developed than upstream tomcod for a given age. On the other hand, greater growth early in
life is insured by occupying warmer, upstream waters during the summer months. 相似文献
68.
Truncation of the distribution of ground-motion residuals 总被引:4,自引:3,他引:1
Recent studies to assess very long-term seismic hazard in the USA and in Europe have highlighted the importance of the upper
tail of the ground-motion distribution at the very low annual frequencies of exceedance required by these projects. In particular,
the use of an unbounded lognormal distribution to represent the aleatory variability of ground motions leads to very high
and potentially unphysical estimates of the expected level of shaking. Current practice in seismic hazard analysis consists
of truncating the ground-motion distribution at a fixed number (ε
max) of standard deviations (σ). However, there is a general lack of consensus regarding the truncation level to adopt. This paper investigates whether
a physical basis for choosing ε
max can be found, by examining records with large positive residuals from the dataset used to derive one of the ground-motion
models of the Next Generation Attenuation (NGA) project. In particular, interpretations of the selected records in terms of
causative physical mechanisms are reviewed. This leads to the conclusion that even in well-documented cases, it is not possible
to establish a robust correlation between specific physical mechanisms and large values of the residuals, and thus obtain
direct physical constraints on ε
max. Alternative approaches based on absolute levels of ground motion and numerical simulations are discussed. However, the choice
of ε
max is likely to remain a matter of judgment for the foreseeable future, in view of the large epistemic uncertainties associated
with these alternatives. Additional issues arise from the coupling between ε
max and σ, which causes the truncation level in terms of absolute ground motion to be dependent on the predictive equation used. Furthermore,
the absolute truncation level implied by ε
max will also be affected if σ is reduced significantly. These factors contribute to rendering a truncation scheme based on a single ε
max value impractical. 相似文献
69.
Hernando Tavera Isabel Bernal Fleur O. Strasser Maria C. Arango-Gaviria John E. Alarcón Julian J. Bommer 《Bulletin of Earthquake Engineering》2009,7(1):71-111
A Mw 7.9 earthquake event occurred on 15 August 2007 off the coast of central Peru, 60 km west of the city of Pisco. This event
is associated with subduction processes at the interface of the Nazca and South American plates, and was characterised by
a complex source mechanism involving rupture on two main asperities, with unilateral rupture propagation to the southeast.
The rupture process is clearly reflected in the ground motions recorded during this event, which include two separate episodes
of strong shaking. The event triggered 18 accelerographic stations; the recordings are examined in terms of their characteristics
and compared to the predictions of ground-motion prediction equations for subduction environments, using the maximum-likelihood-based
method of Scherbaum et al. (Bull Seismol Soc Am 94(6):2164–2185, 2004). Additionally, macroseismic observations and damage
patterns are examined and discussed in the light of local construction practices, drawing on field observations gathered during
the post-earthquake reconnaissance missions. 相似文献
70.
The paper presents an overview of the Upper Adriatic as a contact area between different cultural, social, economic and political entities, producing potential conflicts in the last century. The first part of the 20th century represented a classic example of geopolitical conflict through two World Wars and their related Peace Conferences that deeply impacted the region. Conflicts arising from the mid-century solution of the Trieste question transformed the Upper Adriatic into a laboratory of contemporary political geographic transformation. Changing geopolitical patterns have also modified the political, social and ethnic construction of the Upper Adriatic. The process of creating new international boundaries in the region ended in 1991 with the independence of Slovenia and Croatia. Through these geopolitical transformations in the Upper Adriatic, new political geographic attitudes evolved. Early on, Ratzel's geopolitical principles of defining borders as power barometers between neighbors dominated. More recently, attitudes have reflected modern integrative ideas with a focus on looking for harmony and the elimination of international conflicts. Greater attention has thus been given to the political geography of `everyday life', inter-ethnic relations, and cross-border contacts. Hence, `new' borderlands of the Upper Adriatic are more receptive to integration because they seek to overcome conflicts caused by the division of traditionally homogeneous spaces as local level political and ideological hindrances disappear. The region divided among Italy, Slovenia, and Croatia is becoming a new and special type of European borderland in the new century. 相似文献