Influence of the North Atlantic Oscillation (NAO) on climatic factors and estuarine water temperature on the Basque coast (Bay of Biscay): Comparative analysis of three seasonal NAO indices     

Guillermo Aravena  Fernando Villate  Arantza Iriarte  Ibon Uriarte  Berta Ibáñez 《Continental Shelf Research》2009

The effect of the North Atlantic Oscillation (NAO) indices on climatic conditions and their subsequent influence on water temperature of two Basque estuaries (estuary of Bilbao and estuary of Urdaibai) were assessed by transfer function (TF) models for the period 1997–2006. Results showed that air temperature had an immediate (lag=0) and significant negative response to the NAO, whereas rainfall was not correlated with this climate index. The negative correlation between NAO and air temperature was found to be stronger with the seasonal indices derived from the differences in surface pressure between Iceland and Azores than with that derived from the principal component time-series of the leading eigenvector of the sea-level pressure in an Atlantic sector. The correlations between rainfall and river discharge, and between air temperature and water temperature were positive and highly significant in both estuaries. The response of water temperature to air temperature was immediate in both estuaries, whereas one-quarter lagged responses were also observed in the estuary of Bilbao, which is deeper and more stratified than the estuary of Urdaibai. Our study provides evidence that on the Basque coast the NAO plays an important role in climate variations, which in turn affect estuarine water temperature.  相似文献   

The first electric field pulse of cloud and cloud-to-ground lightning discharges     

Noor Azlinda Ahmad  M. Fernando  Z.A. Baharudin  M. Rahman  V. Cooray  Ziad Saleh  Joseph R. Dwyer  Hamid K. Rassoul 《Journal of Atmospheric and Solar》2010,72(2-3):143-150

In this study, the first electric field pulse of cloud and cloud-to-ground discharges were analyzed and compared with other pulses of cloud discharges. Thirty eight cloud discharges and 101 cloud-to-ground discharges have been studied in this analysis. Pulses in cloud discharges were classified as ‘small’, ‘medium’ and ‘large’, depending upon the value of their relative amplitude with respect to that of the average amplitude of the five largest pulses in the flash. We found that parameters, such as pulse duration, rise time, zero crossing time and full-width at half-maximum (FWHMs) of the first pulse of cloud and cloud-to-ground discharges are similar to small pulses that appear in the later stage of cloud discharges. Hence, we suggest that the mechanism of the first pulse of cloud and cloud-to-ground discharges and the mechanism of pulses at the later stage of cloud discharges could be the same.  相似文献   

The mantle rotation pole position. A solar component     

Fernando Lopes  Jean-Louis Le Mouël  Dominique Gibert 《Comptes Rendus Geoscience》2017,349(4):159-164

The direction of the Earth's rotation axis with respect to the mantle has been studied for more than a century. The time variation of this direction is generally considered to be the sum of three components: the annual wobble, forced by the atmosphere, the Chandler wobble, a free oscillation with a period of 435 days, and the so-called drift of the mean pole. In the present paper, applying the singular spectrum analysis (SSA) technique, we uncover two more components, with smaller amplitude than the three first ones, but well identified, periodic with periods of 11 and 5.5 years, respectively, undoubtedly linked to solar activity. We interpret them tentatively as the result of an exchange of kinetic angular momentum between the atmosphere, in which a flow would be generated by solar activity, and the mantle. The order of magnitude of the required mean winds in the atmosphere computed in the frame of a schematic model is 1 ms^?1, compatible with the observed values of the meridional mean circulation.  相似文献   

Bonding degradation and stress–dilatancy response of weakly cemented sands     

Daniela D. Porcino  Vincenzo Marcianò 《Geomechanics and Geoengineering》2017,12(4):221-233

The progressive bond breakage of artificially cemented sands induced by shear straining was investigated through conventional isotropically consolidated drained triaxial compression tests. Sand specimens were prepared with a low degree of cementation by adopting a chemical grout. Test results were interpreted in terms of two stress–dilatancy theories for cohesive-frictional materials proposed in literature. The influence of debonding on the stress–dilatancy behaviour of cemented sands was analysed with particular emphasis on the ‘delayed dilatancy’ phenomenon. A bonding degradation curve was determined for each test relating the interparticle cohesion (c) to the magnitude of the total plastic strain vector (ε_d) and a bond degradation rate factor (D_c) was assessed from each curve. The maximum value of interparticle cohesion (c₀) before the onset of bond degradation under shearing was found to correspond with a sharp decrease in the soil stiffness of the specimens. The influence of the effective confining stress (p^′_c) on both c₀ and D_c parameters gathered from each test was also ascertained.  相似文献   

From computed tomography to mechanics of granular materials via level set bridge     

Ivan Vlahinić  Reid Kawamoto  Edward Andò  Gioacchino Viggiani  José E. Andrade 《Acta Geotechnica》2017,12(1):85-95

This paper details the ‘level set bridge’: a single platform for the characterization of various aspects of granular micro-mechanics, including grain morphology, grain kinematics, and inter-granular contact. This platform is studied and verified for accuracy using synthetic examples, in particular, its robustness with respect to the variables of image resolution and noise. The level set bridge is then applied to analysis of XRCT images of real 3D triaxial experiments of two types of granular materials. Contact statistics and kinematics are reported inside and outside of the failure band of one, and kinematics inside a failure band are reported in the other, from preload to critical state.  相似文献   

Geophysical characterization of the Ota–Vila Franca de Xira–Lisbon–Sesimbra fault zone, Portugal     

João Carvalho  Taha Rabeh  João Cabral  Fernando Carrilho  Jorge Miguel Miranda 《Geophysical Journal International》2008,174(2):567-584

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Dinophysoid dinoflagellates from subphotic depths:Amphisolenia sp.aff.brevicauda,Dinofurcula tricornuta sp.nov.,and Dinophysis profunda sp.nov.(Dinophysales,Dinophyceae)     

Fernando GóMEZ 《海洋湖沼学报（英文）》2022,(2):703-711

Three species of dinophysoid planktonic dinoflagellates are described from the eastern Mediterranean Sea.Amphisolenia sp.aff.brevicauda was collected at 70-m de...  相似文献   

A Study of the Solar-Like Properties of β Hydri     

Maria Pia Di Mauro  Jørgen Christensen-Dalsgaard  Lucio Paternò 《Astrophysics and Space Science》2003,284(1):229-232

We investigate properties of the internal structure of HR2021, better known as Hydri, a G2 IV subgiant with mass close to solar and for which observations by Bedding et al. (2001) have shown the presence of solar-like oscillations.We have computed models of Hydri,based on updated global parameters,and compared the computed frequencies for the models with the observed oscillation spectrum.  相似文献   

The role of the exchanges through the Strait of Gibraltar on the budget of elements in the Western Mediterranean Sea: consequences of human-induced modifications     

Gómez F 《Marine pollution bulletin》2003,46(6):685-694

The role of the Strait of Gibraltar on the exchanges of substances between Mediterranean Sea and the Atlantic Ocean is reviewed. The previous estimations have been recalculated by using a similar water flux and compared with the river and atmospheric inputs to the Western Mediterranean Sea. The man-induced changes in the dimensions of the Strait of Gibraltar increasing (planning the sill) or reducing of the cross-section by a total or partial dam are discussed. A total dam will control the sea-level rise in the Mediterranean Sea, but an annual increase of major nutrient concentrations of 1-2% could be expected, lower than the rate of increase of the river and atmospheric inputs in the Western Mediterranean Sea. The increase of the cross-section of the Strait by increasing the depth (planning) at the sill could compensate the increase of the external nutrient inputs.  相似文献   

Shear-induced folding in Arsia Mons aureole: Evidence for low-latitude martian glaciations     

Francisco Anguita  Fernando Moreno 《Earth, Moon, and Planets》1992,59(1):11-22

Folds up to 50 km across have been identified on Arsia Mons aureole. Tharsis Province, Mars. The structures, located on Mars for the first time, are close to Aganippe Fossa and other huge faults which have behaved as left-lateral shear zones and then as extensional features. A tectonic scheme is proposed to explain the folds as shear-induced structures. Folding reveals a layered sequence in the aureole, and that is taken as a definitive evidence for its deposition by ice.If at least some of the Tharsis volcanoes aureoles are basal moraines, their study is critical, as they could contain a record of Mars paleoclimatic fluctuations. Martian past frozen lakes or oceans have been proposed, and some sediments found on the northern plains could have been deposited on the bottom of those basins. If this is so, those formations should be layered sequences and could also bear the traces of tectonic stresses, detectable as folds on Viking imagery. Correlation of these two kinds of evidence seems a promising line to tackle the Martian paleoclimatic problem.  相似文献