Initialisation and predictability of the AMOC over the last 50 years in a climate model   总被引：1，自引：1，他引：0  

Didier Swingedouw  Juliette Mignot  Sonia Labetoulle  Eric Guilyardi  Gurvan Madec 《Climate Dynamics》2013,40(9-10):2381-2399

The mechanisms involved in Atlantic meridional overturning circulation (AMOC) decadal variability and predictability over the last 50 years are analysed in the IPSL–CM5A–LR model using historical and initialised simulations. The initialisation procedure only uses nudging towards sea surface temperature anomalies with a physically based restoring coefficient. When compared to two independent AMOC reconstructions, both the historical and nudged ensemble simulations exhibit skill at reproducing AMOC variations from 1977 onwards, and in particular two maxima occurring respectively around 1978 and 1997. We argue that one source of skill is related to the large Mount Agung volcanic eruption starting in 1963, which reset an internal 20-year variability cycle in the North Atlantic in the model. This cycle involves the East Greenland Current intensity, and advection of active tracers along the subpolar gyre, which leads to an AMOC maximum around 15 years after the Mount Agung eruption. The 1997 maximum occurs approximately 20 years after the former one. The nudged simulations better reproduce this second maximum than the historical simulations. This is due to the initialisation of a cooling of the convection sites in the 1980s under the effect of a persistent North Atlantic oscillation (NAO) positive phase, a feature not captured in the historical simulations. Hence we argue that the 20-year cycle excited by the 1963 Mount Agung eruption together with the NAO forcing both contributed to the 1990s AMOC maximum. These results support the existence of a 20-year cycle in the North Atlantic in the observations. Hindcasts following the CMIP5 protocol are launched from a nudged simulation every 5 years for the 1960–2005 period. They exhibit significant correlation skill score as compared to an independent reconstruction of the AMOC from 4-year lead-time average. This encouraging result is accompanied by increased correlation skills in reproducing the observed 2-m air temperature in the bordering regions of the North Atlantic as compared to non-initialized simulations. To a lesser extent, predicted precipitation tends to correlate with the nudged simulation in the tropical Atlantic. We argue that this skill is due to the initialisation and predictability of the AMOC in the present prediction system. The mechanisms evidenced here support the idea of volcanic eruptions as a pacemaker for internal variability of the AMOC. Together with the existence of a 20-year cycle in the North Atlantic they propose a novel and complementary explanation for the AMOC variations over the last 50 years.  相似文献   

Results from the Eso Large Program on Transneptunian Objects and Centaurs     

Boehnhardt  Hermann  Barucci  Antonella  Delsanti  Audrey  De Bergh  Catherine  Doressoundiram  Alain  Romon  Jennifer  Dotto  Elisabetta  Tozzi  Gianpaolo  Lazzarin  Monica  Fornasier  Sonia  Peixinho  Nuno  Hainaut  Olivier  Davies  John  Rousselot  Philippe  Barrera  Luis  Birkle  Kurt  Meech  Karen  Ortiz  JoseLuis  Sekiguchi  Tomohiko  Watanabe  Jun-ichi  Thomas  Nick  West  Richard 《Earth, Moon, and Planets》2003,92(1-4):145-156

BVRI photometry of 107 TNOs and Centaurs establishes the range of spectral gradients to be between –5 to 55%/100 nm (with one exception). A cluster of very red Cubewanos is firmly identified in orbits of low inclination and eccentricity beyond 40 AU from the Sun. Further correlations between surface colours and dynamical parameters (inclination and perihelion distance) are suggested for Cubewanos and scattered disk objects, but lack complete confidence for their reality. Plutinos and Centaurs do not show any clear correlation between surface colours and orbital parameters. We present in this paper 12 spectra obtained in the visible region and nine of them for which we obtained also near infrared spectra up to 2.4 microns. A few other objects have been observed, but the data are still under reduction and analysis. The principal reported results obtained are: (i) a wide range of visible slopes; (ii) evidence for surface variations on 2001 PT₁₃; and (iii) possible detection of few percent of water ice (1999 TC_36}, 2000 EB₁₇₃, 1999 DE₉, 2001 PT₁₃, 2000 QC₂₄₃, 1998 SG₃₅).  相似文献   

Systems of colliding bodies in a gravitational field: Impact velocity,inelasticity and sizes distributions     

Sonia Clairemidi 《Earth, Moon, and Planets》1987,38(3):237-248

We study numerically the dynamical evolution of a system of colliding bodies. Collisions are inelastic and the coefficient of rebound is a function of the impat velocity. Various functions are used. The system can reach an equilibrium state characterized by a finite thickness independently on the sense of variation of the functions. Within the frame of various distributions of the body sizes we observe a segregation rather than equipartition of the kinetic energy of random motions.  相似文献   

Mantle and crustal processes in the magmatism of the Campania region: inferences from mineralogy, geochemistry, and Sr–Nd–O isotopes of young hybrid volcanics of the Ischia island (South Italy)     

Massimo D’Antonio  Sonia Tonarini  Ilenia Arienzo  Lucia Civetta  Luigi Dallai  Roberto Moretti  Giovanni Orsi  Mariachiara Andria  Alberto Trecalli 《Contributions to Mineralogy and Petrology》2013,165(6):1173-1194

Ischia, one active volcano of the Phlegraean Volcanic District, prone to very high risk, is dominated by a caldera formed 55 ka BP, followed by resurgence of the collapsed area. Over the past 3 ka, the activity extruded evolved potassic magmas; only a few low-energy explosive events were fed by less evolved magmas. A geochemical and Sr–Nd–O isotope investigation has been performed on minerals and glass from products of three of such eruptions, Molara, Vateliero, and Cava Nocelle (<2.6 ka BP). Data document strong mineralogical, geochemical, and isotopic heterogeneities likely resulting from mingling/mixing processes among mafic and felsic magmas that already fed the Ischia volcanism in the past. Detailed study on the most mafic magma has permitted to investigate its origin. The mantle sector below Ischia underwent subduction processes that modified its pristine chemical, isotopic, and redox conditions by addition of ≤1 % of sediment fluids/melts. Similar processes occurred from Southeast to Northwest along the Apennine compressive margin, with addition of up to 2.5 % of sediment-derived material. This is shown by volcanics with poorly variable, typical δ¹⁸O mantle values, and ⁸⁷Sr/⁸⁶Sr progressively increasing toward typical continental crust values. Multiple partial melting of this modified mantle generated distinct primary magmas that occasionally assimilated continental crust, acquiring more ¹⁸O than ⁸⁷Sr. At Ischia, 7 % of Hercynian granodiorite assimilation produced isotopically distinct, K-basaltic to latitic magmas. A SW–NE regional tectonic structure gave these magmas coming from large depth the opportunity to mingle/mix with felsic magmas stagnating in shallower reservoirs, eventually triggering explosive eruptions.  相似文献   

Yields of suspended sediment and dissolved solids from the Andean basins of Ecuador     

Elisa Armijos  Alain Laraque  Sonia Barba  Luc Bourrel  Catalina Ceron  Christelle Lagane 《水文科学杂志》2013,58(7):1478-1494

Abstract

Water discharge and suspended and dissolved sediment data from three rivers (Napo, Pastaza and Santiago) in the Ecuadorian Amazon basin and a river in the Pacific basin (Esmeraldas) over a 9-year period, are presented. This data set allows us to present: (a) the chemical weathering rates; (b) the erosion rates, calculated from the suspended sediment from the Andean basin; (c) the spatio-temporal variability of the two regions; and (d) the relationship between this variability and the precipitation, topography, lithology and seismic activity of the area. The dissolved solids load from the Esmeraldas basin was 2 × 10⁶ t year^-1, whereas for the Napo, Pastaza and Santiago basins, it was 4, 2 and 3 × 10⁶ t year^-1, respectively. For stations in the Andean piedmont of Ecuador, the relationship between surface sediment and the total sediment concentration was found to be close to one. This is due to minimal stratification of the suspended sediment in the vertical profile, which is attributed to turbulence and high vertical water speeds. However, during the dry season, when the water speed decreases, sediment stratification appears, but this effect can be neglected in the sediment flux calculations due to low concentration rates. The suspended sediment load in the Pacific basin was 6 × 10⁶ t year^-1, and the total for the three Amazon basins was 47 × 10⁶ t year^-1. The difference between these contributions of the suspended sediment load is likely due to the tectonic uplift and the seismic and volcanic dynamics that occur on the Amazon side.

Editor Z.W. Kundzewicz

Citation Armijos, E., Laraque, A., Barba, S., Bourrel, L., Ceron, C., Lagane, C., Magat, P., Moquet, J.-S., Pombosa, R., Sondag, F., Vauchel, P., Vera, A., and Guyot, J.L., 2013. Yields of suspended sediment and dissolved solids from the Andean basins of Ecuador. Hydrological Sciences Journal, 58 (7), 1478–1494.  相似文献   

Performance of the L’Aquila (central Italy) gas distribution network in the 2009 (\mathrm{{M}}_\mathrm{{w}} 6.3) earthquake     

Simona Esposito  Sonia Giovinazzi  Ludovica Elefante  Iunio Iervolino 《Bulletin of Earthquake Engineering》2013,11(6):2447-2466

Despite the seismic vulnerability of gas systems and the significance of the direct and indirect consequences that loss functionality might have on large communities, the analysis of the earthquake performance and of post-earthquake management for this kind of distribution networks appears under-represented in the international literature, with respect to other lifeline systems. To contribute on this matter, the study presented comprises an investigation of the impact of L’Aquila 2009 earthquake ( $\text{ M }_\mathrm{w}$ 6.3) on the performance of the local medium- and low-pressure gas distribution networks. The assessment of the physical impact of the earthquake to the buried components of network, namely pipes, valves, and demand nodes, was carried out when processing post-earthquake repair activity reports. Repair data, along with geometrical and constructive features, were collected in a geographic information system linked to the digitized maps of the network, and compared with the interpolated map of recorded transient ground motion, measured in terms of peak ground velocity (i.e., a $Shakemap^\mathrm{TM}$ ). The impact of permanent ground deformation was also investigated and found to be limited in the study area. The resulting observed repair rates (number of repairs per km), presented for different pipeline materials, were compared with repair ratio fragility functions available in literature, showing relatively agreement especially to those for steel pipes, likely also because of the uncertainties in the estimations. Finally, the management of the L’Aquila gas system in the emergency phase and the resilience (functionality recover versus time) of the system was discussed.  相似文献   

Parameterization of historical earthquakes in Switzerland   总被引：1，自引：1，他引：0  

Sonia álvarez-Rubio  Philipp K?stli  Donat F?h  Souad Sellami  Domenico Giardini 《Journal of Seismology》2012,16(1):1-24

Macroseismic earthquake parameters of historical events have been reassessed in the framework of the update of the Earthquake Catalogue of Switzerland ECOS-09. The Bakun and Wentworth method (Bakun and Wentworth 1997) has been used to assess location, magnitude, and, when possible, focal depth. We apply a two-step procedure. Intensity attenuation is assessed first by fitting a model with a logarithmic and a linear term, using a set of 111 earthquakes. The magnitude range is 3 and 5.8. Then, intensity to magnitude relation is developed. A subset of the 111 events, all having an instrumental moment magnitude, was used to perform this intensity to magnitude calibration. Five final calibration strategies were developed based on different intensity calibration datasets, regionalized or non-regionalized models, and fixed or variable source depth. The final assessment of the macroseismic earthquake parameters is based on an expert judgment procedure, using the results derived from all five strategies, and taking into consideration the historical knowledge available for the particular earthquake. A bootstrap procedure has been applied to assess the uncertainty of parameters. Indicative lower and upper bounds of uncertainty are derived from distributions of location and magnitude for a number of events, obtained through bootstrap sampling of the intensity field and of the single intensity values. The final uncertainties are given in terms of parameter uncertainty classes already used in previous versions of the earthquake catalogue of Switzerland.  相似文献   

Forest biodiversity assessment in Peruvian Andean Montane cloud forest     

Alicia Ledo  Sonia Condés  Iciar Alberdi 《山地科学学报》2012,9(3):372-384

Cloud forests are unusual and fragile habitats, being one of the least studied and least understood ecosystems. The tropical Andean dominion is considered one of the most significant places in the world as regards biological diversity, with a very high level of endemism. The biodiversity was analysed in an isolated remnant area of a tropical montane cloud forest known as the "Bosque de Neblina de Cuyas", in the North of the Peruvian Andean range. Composition, structure and dead wood were measured or estimated. The values obtained were compared with other cloud forests. The study revealed a high level of forest biodiversity, although the level of biodiversity differs from one area to another: in the inner areas, where human pressure is almost inexistent, the biodiversity values increase. The high species richness and the low dominance among species bear testimony to this montane cloud forest as a real enclave of biodiversity.  相似文献   

Response spectra for the deep sediment-filled Rhône Valley in the Swiss Alps     

Hans-Balder Havenith  Donat Fäh  Sonia Alvarez-Rubio  Daniel Roten 《Soil Dynamics and Earthquake Engineering》2009

We present numerical modeling of earthquake ground motion for various profiles across the Swiss Rhône Valley and characterize the seismic response in terms of spectral acceleration. First, we evaluate the relative amplification of 2D with respect to 1D response. Then, we show how the selected bedrock spectrum influences the response spectra of the valley sites. Particular attention is paid to how the internal sediment structure and the often weakly constrained Q-factor shape the seismic response. Results obtained for the different profiles are compared with reference spectra (Swiss building code and Eurocode 8) and for one profile with recorded data as well. From this comparison, we infer that the surficial layer strongly influences spectral acceleration values between 0.1 and 1 s. The total thickness of sediments significantly affects the seismic response at longer periods around the fundamental period of the studied valley sections between 1.8 and 3.6 s.  相似文献   

From climate change impacts to the development of adaptation strategies: Challenges for agriculture in Europe   总被引：1，自引：0，他引：1  

Ana Iglesias  Sonia Quiroga  Marta Moneo  Luis Garrote 《Climatic change》2012,112(1):143-168

This study links climate change impacts to the development of adaptation strategies for agriculture in Europe. Climate change is expected to intensify the existing risks, particularly in southern regions, and create new opportunities in some northern areas. These risks and opportunities are characterised and interpreted across European regions by analysing over 300 highly relevant publications that appeared in the last decade. The result is a synthesis of the reasons for concern for European agricultural regions. The need to respond to these risks and opportunities is addressed by evaluating the costs and benefits of a number of technical and policy actions. The results highlight the importance of enhanced water use efficiency as a critical response to climate risks and the need for a more effective extension service. These results aim to assist stakeholders as they take up the adaptation challenge and develop measures to reduce the vulnerability of the sector to climate change.  相似文献