Climate change in terms of modes of atmospheric variability and circulation regimes over southern South America     

Silvina A. Solman  Herve Le Treut 《Climate Dynamics》2006,26(7-8):835-854

The simulated low-frequency variability patterns of the atmospheric circulation, ranging from interannual to interdecadal timescales, are studied in an area encompassing southern South America. The experiment is a transient simulation performed with the IPSL CCM2 coupled global model, in which the greenhouse forcing is continuously increasing. The main modes of low-frequency variability are found to remain stationary throughout the simulation, suggesting they depend more on the internal dynamics of the atmospheric flow than on its external forcing. Inspection of the circulation regimes that represent the more recurrent patterns at interannual and interdecadal timescales showed that climate change manifests itself as a change in regime population, suggesting that the negative phase of the Antarctic Oscillation-like pattern becomes more frequented in a climate change scenario. Changes of regime occurrence are superimposed to a positive trend whose spatial pattern is reminiscent of the structure of the Antarctic Oscillation-mode of variability. Moreover, it resembles the spatial patterns of those regimes that show a significant change in population. The change in regime frequencies of the circulation patterns of low-frequency variability are in opposite phase with respect to the trend, thus, the behaviour of these patterns of variability, superimposed to a changing mean state, modulates the climate change signal. The analysis of the high frequencies, in terms of recurrent patterns representing intraseasonal and synoptic-scale of variability, shows no significant changes in regime characteristics, concerning both spatial and temporal behaviour.  相似文献   

Blue Compact Galaxies at Redshifts Z=0.2-1.3     

R. Guzmán 《Astrophysics and Space Science》1998,263(1-4):127-130

We study the nature of faint blue compact galaxies (BCGs) at redshifts z ∼ 0.2 - 1.3 using Keck and HST. Despite being very luminous (L_B ∼ L^*), most distant BCGs have masses M ∼ 10¹⁰M_⊙, i.e., they are dwarf stellar systems. The majority of these galaxies have colors, sizes, surface brightnesses, luminosities, velocity widths, excitations, star formation rates (SFR), and mass-to-light ratios characteristic of the most luminous nearby HII galaxies. The more massive BCGs form a more heterogeneous class of evolved starburst, similar to local disk starburst galaxies. Without additional star formation, HII-like BCGs will most likely fade to resemble today's spheroidal galaxies such as NGC 205. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Bioindication potential of carbonic anhydrase activity in anemones and corals     

Gilbert AL  Guzmán HM 《Marine pollution bulletin》2001,42(9):742-744

Activity levels of carbonic anhydrase (CA) were assessed in anemones Condylactis gigantea and Stichodactyla helianthus with laboratory exposures to copper, nickel, lead, and vanadium, and also in animals collected from polluted vs pristine field sites. CA activity was found to be decreased with increase in metal concentration and also in animals collected from the polluted field site. Preliminary assessments to adapt the CA assay for use in the widespread coral Montastraea cavernosa show decreased CA activity in specimens from the polluted field site and provide an avenue for future research aimed at more thoroughly describing coral CA activity for potential application in bioindication.  相似文献   

3-D crustal-scale gravity model of the San Rafael Block and Payenia volcanic province in Mendoza,Argentina     

Daniel Richarte  Marianela Lupari  Agustina Pesce  Silvina Nacif  Mario Gimenez 《地学前缘(英文版)》2018,9(1):239-248

The San Rafael Block(SRB)is part of one of the main retroarc volcanic provinces in southern Central Andes in Mendoza,Argentina.This block is located in the Andean foothills between the orogenic front and foreland basement uplifts of late Miocene age.In order to analyze the geochronological evolution of the Quaternary volcanism in the region,several geologic and geophysical studies have been conducted.Nevertheless,the crust,where the SRB is located,has not been well characterized yet.Based on gravimetric and magnetic data,together with isostatic and elastic thickness analyses,we modeled the crustal structure of the area.Information obtained has allowed us to understand the crust where the SRB and the Payenia volcanic province are located.Bouguer anomalies indicate that the SRB presents higher densities to the North of Cerro Nevado and Moho calculations suggest depths for this block between 40 and 50 km.Determinations of elastic thickness would indicate that the crust supporting the San Rafael Block presents values of approximately 10 km,being enough to support the block loading.However,in the Payenia region,elastic thickness values are close to zero due to the regional temperature increase.  相似文献   

Local high relief at the southern margin of the Andean plateau by 9 Ma: evidence from ignimbritic valley fills and river incision     

Carolina Montero‐López  Manfred R. Strecker  Taylor F. Schildgen  Fernando Hongn  Silvina Guzmán  Bodo Bookhagen  Masafumi Sudo 《地学学报》2014,26(6):454-460

A valley‐filling ignimbrite re‐exposed through subsequent river incision at the southern margin of the Andean (Puna) plateau preserves pristine geological evidence of pre‐late Miocene palaeotopography in the north western Argentine Andes. Our new ⁴⁰Ar/³⁹Ar dating of the Las Papas Ignimbrites yields a plateau age of 9.24 ± 0.03 Ma, indicating valley‐relief and orographic‐barrier conditions comparable to the present‐day. A later infill of Plio–Pleistocene coarse conglomerates has been linked to wetter conditions, but resulted in no additional net incision of the Las Papas valley, considering that the base of the ignimbrite remains unexposed in the valley bottom. Our observations indicate that at least 550 m of local plateau margin relief (and likely >2 km) existed by 9 Ma at the southern Puna margin, which likely aided the efficiency of the orographic barrier to rainfall along the eastern and south eastern flanks of the Puna and causes aridity in the plateau interior.  相似文献   

Evaluating uncertainties in regional climate simulations over South America at the seasonal scale   总被引：1，自引：0，他引：1  

Silvina A. Solman  Natalia L. Pessacg 《Climate Dynamics》2012,39(1-2):59-76

This work focuses on the evaluation of different sources of uncertainty affecting regional climate simulations over South America at the seasonal scale, using the MM5 model. The simulations cover a 3-month period for the austral spring season. Several four-member ensembles were performed in order to quantify the uncertainty due to: the internal variability; the definition of the regional model domain; the choice of physical parameterizations and the selection of physical parameters within a particular cumulus scheme. The uncertainty was measured by means of the spread among individual members of each ensemble during the integration period. Results show that the internal variability, triggered by differences in the initial conditions, represents the lowest level of uncertainty for every variable analyzed. The geographic distribution of the spread among ensemble members depends on the variable: for precipitation and temperature the largest spread is found over tropical South America while for the mean sea level pressure the largest spread is located over the southeastern Atlantic Ocean, where large synoptic-scale activity occurs. Using nudging techniques to ingest the boundary conditions reduces dramatically the internal variability. The uncertainty due to the domain choice displays a similar spatial pattern compared with the internal variability, except for the mean sea level pressure field, though its magnitude is larger all over the model domain for every variable. The largest spread among ensemble members is found for the ensemble in which different combinations of physical parameterizations are selected. The perturbed physics ensemble produces a level of uncertainty slightly larger than the internal variability. This study suggests that no matter what the source of uncertainty is, the geographical distribution of the spread among members of the ensembles is invariant, particularly for precipitation and temperature.  相似文献   

Finite element methodology for the evaluation of soil damping in LNG tanks supported on homogeneous elastic halfspace     

Diego Peña Ruiz  Santiago Guzmán Gutiérrez 《Bulletin of Earthquake Engineering》2015,13(3):755-775

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A revision of soft proton scattering at grazing incidence and its implementation in the <Emphasis Type="SmallCaps">geant</Emphasis>4 toolkit     

Alejandro Guzmán  Emanuele Perinati  Sebastian Diebold  Chris Tenzer  Andrea Santangelo 《Experimental Astronomy》2017,44(3):401-411

The scattering of soft protons inside the Wolter-type optics of X-ray observatories has been proven to concentrate these particles onto the focal plane instruments. The funneling of these protons increases the instrumental background and can also contribute to the degrading of the detectors. The instrumental background and degradation of the detector’s performance experienced by Chandra and XMM-Newton is significantly larger than what was expected on the basis of previous Monte Carlo simulations. For Chandra the main issue is the degradation of the energy resolution due to lattice displacements in the detectors. For XMM the contribution to the instrumental background is more significant. In between, new laboratory measurements as well as a revision of the theory are needed to correctly assess the impact of the environmental radiation for future missions. In this publication we present a Geant4 class that will allow future users to select between either theoretical models or measured data to simulate the scattering of soft protons at grazing angles. To develop this method, we revisit the theory of elastic scattering of protons on polished surfaces and implement these approaches into Geant4. We also implemented recently performed measurements using parts of eROSITA (extended ROentgen Survey with an Imaging Telescope Array) mirror shells as scattering targets as another scattering model to be used within the Geant4 toolkit.  相似文献   

Homogeneous Universes in Extended Inflation I     

Enrique Guzmán 《Astrophysics and Space Science》1997,249(2):179-188

We have found that for the Bianchi types I–II–III–V in the Brans-Dicke theory, the scalar field of the theory φ has the same form in the isotropic case. It is shown that the isotropization of the Universe occurs in a very short time when the Universe is dominated by vacuum energy, proving that an isotropic Robertson-Walker model is a good approximation to use in the extended inflation scenario. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

General vacuum solution for Brans-Dicke-Bianchi type-II     

Enrique Guzmán 《Astrophysics and Space Science》1991,179(2):331-334

In this paper we have obtained the general vacuum solution for Bianchi type-II in the Brans-Dicke theory for total anistropyR ₁R ₂R ₃. It is known that by use of our method, we can find the general solution for Bianchi type-II vacuum case in the general relativity theory, first given by Taub (1951). Some physical properties of this model are also discussed.  相似文献