Heatwaves in Europe: areas of homogeneous variability and links with the regional to large-scale atmospheric and SSTs anomalies   总被引：1，自引：1，他引：0  

Andrea F. Carril  Silvio Gualdi  Annalisa Cherchi  Antonio Navarra 《Climate Dynamics》2008,30(1):77-98

This work presents a methodology to study the interannual variability associated with summertime months in which extremely hot temperatures are frequent. Daily time series of maximum and minimum temperature fields (T _max and T _min, respectively) are used to define indexes of extreme months based on the number of days crossing thresholds. An empirical orthogonal function (EOF) analysis is applied to the monthly indexes. EOF loadings give information about the geographical areas where the number of days per month with extreme temperatures has the largest variability. Correlations between the EOF principal components and the time series of other fields allow plotting maps highlighting the anomalies in the large scale circulation and in the SSTs that are associated with the occurrence of extreme events. The methodology is used to construct the “climatology” of the extremely hot summertime months over Europe. In terms of both interannual and intraseasonal variability, there are three regions in which the frequency of the extremely hot days per month homogeneously varies: north-west Europe, Euro-Mediterranean and Eurasia region. Although extremes over those regions occur during the whole summer (June to August), the anomalous climatic conditions associated with frequent heatwaves present some intraseasonal variability. Extreme climate events over the north-west Europe and Eurasia are typically related to the occurrence of blocking situations. The intraseasonal variability of those patterns is related to the amplitude of the blocking, the relative location of the action centre and the wavetrain of anomalies downstream or upstream of the blocking. During June and July, blocking situations which give extremely hot climate conditions over north-west Europe are also associated with cold conditions over the eastern Mediterranean sector. The Euro-Mediterranean region is a transition area in which extratropical and tropical systems compete, influencing the occurrence of climate events: blockings tend to be related to extremely hot months during June while baroclinic anomalies dominate the variability of the climate events in July and August. We highlight that our method could be easily applied to other regions of the world, to other fields as well as to model outputs to assess, e.g. the potential change of extreme climate events in a warmer climate.  相似文献   

Denudation history of the Bocaina Plateau, Serra do Mar, southeastern Brazil: Relationships to Gondwana breakup and passive margin development   总被引：1，自引：0，他引：1  

Silvio T. Hiruma  Claudio Riccomini  May C. Modenesi-Gauttieri  Peter C. Hackspacher  Julio C. Hadler Neto  Ana O.B. Franco-Magalhes 《Gondwana Research》2010,18(4):674-687

The Bocaina Plateau, which is situated on the eastern flank of the continental rift of southeastern Brazil, is the highest part of the Serra do Mar. Topographic relief in this area is suggested to be closely related to its complex tectono-magmatic evolution since the breakup of Western Gondwana and opening of the South Atlantic Ocean. Apatite fission track ages and track length distributions from 27 basement outcrops were determined to assess these hypotheses and reconstruct the denudation history of the Bocaina Plateau. The ages range between 303 ± 32 and 46 ± 5 Ma, and are significantly younger than the stratigraphic ages. Mean track lengths vary from 13.44 ± 1.51 to 11.1 ± 1.48 μm, with standard deviations between 1.16 and 1.83 μm. Contrasting ages within a single plateau and similar ages at different altitudes indicate a complex regional tectonothermal evolution. The thermal histories inferred from these data imply three periods of accelerated cooling related to the Early Cretaceous continental breakup, Early Cretaceous alkaline magmatism, and the Paleogene evolution of the continental rift of southeastern Brazil. The oldest fission track ages (> 200 Ma) were obtained in the Serra do Mar region, suggesting that these areas were a long-lived source of sediments for the Paraná, Bauru, and Santos basins.  相似文献   

The Speciation of (CH3)2Sn2+ in Electrolyte Solution Containing the Major Components of Natural Waters     

Claudia Foti  Antonio Gianguzza  Frank J. Millero  Silvio Sammartano 《Aquatic Geochemistry》1999,5(4):381-398

Hydrolysis constants of dimethyltin(IV) cation, in different salt solutions (CaCl₂: 0.15 I 0.90; MgCl₂: 0.30 I 0.60; NaCl-–NaClO₄, NaCl-–NaNO₃ mixtures: I = 3; NaCl-–Na₂SO₄ mixtures: I = 1 mol dm^-3) were determined by potentiometric ([H⁺]-glass electrode) measurements. These data, together with previous data (De Stefano et al., 1996b) were interpreted in terms of DHT (Debye–Hückel type) and Pitzer equations. The mixed electrolyte solution results also allowed us to obtain and parameters for the Pitzer equation. Calorimetric measurements were made at different ionic strengths in order to find the temperature dependence of hydrolysis constants and of the relative interaction parameters. The body of results allows us to determine the speciation of natural waters in a wide range of ionic strengths and temperatures.  相似文献   

Il graduale aumento del livello del mare lungo le coste Italiane     

Prof. Dr. Silvio Polli 《Pure and Applied Geophysics》1953,25(1):123-129

Riassunto Aderendo alle proposte del Comitato del Livello Medio Marino della Associazione Internazionale di Oceanografia Fisica, sono stati calcolati, col metodo dei minimi quadrati, i valori dellavariazione secolare e dellavariazione standard dei livelli medi marini relativi ad 11 porti italiani. Il valore medio della variazione per i mari italiani corrisponde ad un aumento del livello marino di 16 cm/secolo, quello di tutti i mari della Terra è di 11 cm/secolo. La differenza in più per i mari italiani è dovuta ad un contemporaneo abbassamento delle zone costiere di Napoli e di Venezia.

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Summary Complying with the proposals of the Committee on Mean Sea Level of the International Association of Physical Oceanography, they were calculated, by the least square method; the values of the secular variation and of the standard deviation of the mean sea levels of eleven Italian stations. The mean value of the variation for the Italian seas corresponds to an encrease of 16 cm/100 years of the sea level; that of the whole seas of the Earth is of 11 cm/100 years. The highest value for the Italian seas it is due to a contemporaneous sinking of Neaple and Venice coasts.

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Comunicazione presentata il 10 Aprile 1953 alla I.a Assemblea Generale della Società Italiana di Geofisica e Meteorologia (Genova, 10–12 Aprile 1953).  相似文献   

Geochronology of the medium to high-grade metamorphic units of the Peloritani Mts., Sicily     

Sofia?De GregorioEmail author  Silvio?G.?Rotolo  Igor?M.?Villa 《International Journal of Earth Sciences》2004,93(1):163-168

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Transition from mildly-tholeiitic to calc-alkaline suite: the case of Chichontepec volcanic centre, El Salvador, Central America     

Silvio G. Rotolo  Francesca Castorina 《Journal of Volcanology and Geothermal Research》1998,86(1-4)

The Chichontepec volcano is a Plio-Pleistocene composite volcano that erupted lavas ranging from high-alumina basalts to dacites. It experienced a caldera-forming paroxysmal eruption during the early Pleistocene. Pre-caldera lavas are mildly tholeiitic and they evolved mainly by low pressure crystal fractionation, notwithstanding the fact that most mafic lavas (low-MgO high-alumina basalts) retain traces of polybaric evolution. Conversely, post-caldera lavas, which are mainly pyroxene andesites, are clearly calc-alkaline, having evolved by open-system crystal fractionation. Sr–Nd isotopic data and trace elements characteristics indicate that the same mantle source was involved in the petrogenesis of these series. Modelling the AFC process showed that it did not play any role in the petrogenesis of these rocks; a crystal fractionation model is considered to be more relevant. A slight variation in the fractionating assemblage could have caused the transition from an early mildly tholeiitic trend to a late calc-alkaline one. Mineralogical evidence, mass-balance calculations and elemental chemistry support this hypothesis, assuming that the greater amount of pyroxene on the liquidus is at the expense of plagioclase; this would have prevented the trend in iron enrichment.  相似文献   

Early Paleozoic Structural and Metamorphic Evolution of Western Sierra de San Luis (Argentina), in Relation to Cuyania Accretion     

Pablo Diego GonzAlez  Ana Maria Sato  Eduardo Jorge Llambias  Miguel A.S. Basei  Silvio R.F. Vlach 《Gondwana Research》2004,7(4):1157-1170

Structural, metamorphic and isotopic data obtained from the Nogoli Metamorphic Complex of western Sierra de San Luis indicate that the Early Paleozoic Famatinian Orogeny overprinted an already structured and metamorphosed older basement. The older geological features are relict NW trending fabric associated with high-grade (amphibolite facies) regional metamorphism preserved within thin strips of schists and paragneisses and in the core of mafic to ultramafic lenses. Arc magmatism, medium P (Barrovian type)/high T (amphibolite to granulite facies) regional metamorphism and penetrative NNE to NE trending foliation are related to the building of the Famatinian orogenic belt. The P-T conditions of the Famatinian prograde metamorphism reached a pressure peak of ca. 8 kb, with a thermal peak from -750°C up to -820°C. U-Pb conventional and chemical dating and Ar-Ar plateau ages constrain the peak of the main orogenic phase related to the Famatinian belt to 470–457 Ma (Early to Mid-Ordovician). Greenschist facies retrograde metamorphism closely associated with shear zones and secondary Ar-Ar plateau and Sm-Nd ages suggest that a late to post-orogenic phase of the Famatinian belt was active at least since -445 Ma. This phase continued during the Silurian to Late Devonian times through multiple reactivation of early shear zones. The Famatinian Orogeny reset a previous thermal history and therefore, the timing of the relict fabric could not be constrained conclusively with radiometric dates. Despite this difficulty, a range of 520 to 490 Ma suggests some inheritance from Pampean events registered by the older NW-SE fabric. The Early to Mid-Ordovician regional metamorphism and ductile deformation of the western Sierra de San Luis is interpreted as the orogenic effects of the collision of the allochthonous Cuyania terrane with the autochthonous proto-Pacific margin of Gondwana during the Famatinian Orogeny.  相似文献   

Observations of volcanic tremor during the January–February 2005 eruption of Mt. Veniaminof,Alaska     

Silvio De Angelis  Stephen R. McNutt 《Bulletin of Volcanology》2007,69(8):927-940

Mt. Veniaminof, Alaska Peninsula, is a stratovolcano with a summit ice-filled caldera containing a small intracaldera cone and active vent. From January 2 to February 21, 2005, Mt. Veniaminof erupted. The eruption was characterized by numerous small ash emissions (VEI 0 to 1) and accompanied by low-frequency earthquake activity and volcanic tremor. We have performed spectral analyses of the seismic signals in order to characterize them and to constrain their source. Continuous tremor has durations of minutes to hours with dominant energy in the band 0.5–4.0 Hz, and spectra characterized by narrow peaks either irregularly (non-harmonic tremor) or regularly spaced (harmonic tremor). The spectra of non-harmonic tremor resemble those of low-frequency events recorded simultaneously with surface ash explosions, suggesting that the source mechanisms might be similar or related. We propose that non-harmonic tremor at Mt. Veniaminof results from the coalescence of gas bubbles while low-frequency events are related to the disruption of large gas pockets within the conduit. Harmonic tremor, characterized by regular and quasi-sinusoidal waveforms, has duration of hours. Spectra containing up to five harmonics suggest the presence of a resonating source volume that vibrates in a longitudinal acoustic mode. An interesting feature of harmonic tremor is that frequency is observed to change over time; spectral lines move towards higher or lower values while the harmonic nature of the spectra is maintained. Factors controlling the variable characteristics of harmonic tremor include changes in acoustic velocity at the source and variations of the effective size of the resonator.  相似文献   

Siliceous productivity changes in Gulf of Ancud sediments (42°S, 72°W), southern Chile,over the last ∼150 years     

Lorena Rebolledo  Humberto E. González  Práxedes Muñoz  José L. Iriarte  Carina B. Lange  Silvio Pantoja  Marco Salamanca 《Continental Shelf Research》2011,31(3-4):356-365

We evaluated changes in siliceous export production and the source of organic matter preserved in sediment core MD07-3109H recovered from the Gulf of Ancud, Chiloé Inner Sea (42°S, 72°W, water column depth: 328 m), southern Chile. We analyzed the abundance of siliceous microfossils (diatoms, silicoflagellates, sponge spicules, Chrysophyte cysts, phytoliths), geochemical proxies (weight percent silicon %Si_OPAL, organic carbon, total nitrogen, C/N molar), and sediment stable isotopes (δ¹³C_org, δ¹⁵N). Chronology based on ²¹⁰Pb and ¹⁴C provided an accumulated age of 144 years at the base of the core.Sediments of core MD07-3109H are predominantly marine in origin, averaging δ¹³C_org=–20.75‰±0.82, δ¹⁵N=8.7±0.35‰, and C/N=8.76±0.36. Marine diatoms compose 94% of the total assemblage of siliceous microfossils. Our record of productivity based on the mass accumulation rates of organic carbon, total nitrogen, Si_OPAL, and total diatoms showed high values between 1863 and 1869 AD followed by a declining trend until 1921 AD, a transition period from 1921 to 1959 AD with fluctuating values, and a clear decreasing pattern from 1960 AD to the present. This marked reduction in productivity was associated with decreased precipitation and Puelo River streamflow (41°S), as well as a warmer and more stratified water column, especially since the 1980s.  相似文献   

A long-term climatology of medicanes     

Leone Cavicchia  Hans von Storch  Silvio Gualdi 《Climate Dynamics》2014,43(5-6):1183-1195

Medicanes, intense and destructive mesoscale cyclones exhibiting several similarities with tropical hurricanes, are known to struck occasionally the Mediterranean Sea. Thanks to a high-resolution dynamical downscaling effort, we are able to study for the first time the long-term climatology of those rare storms in a systematic way. The distribution of medicanes frequency in space and time is discussed, and the environmental factors responsible for their formation are investigated. We find that medicanes develop in those areas of the Mediterranean region where intrusions of cold air in the upper troposphere can produce configurations of thermodynamical disequilibrium of the atmosphere similar to those associated with the formation of tropical cyclones.  相似文献