A bin-microphysics cloud model with high-order, positive-definite advection     

Alexandre A. Costa  Gerson P. Almeida  Antnio Jos C. Sampaio 《Atmospheric Research》2000,55(3-4)

An axisymmetric, anelastic model of a convective cloud is described. The model comprises prognostic equations for the azimuthal vorticity, the perturbation potential temperature, the perturbation water vapor mixing ratio, 44 categories of cloud condensation nuclei, and 100 categories of liquid-phase hydrometeors. Results from a control simulation show that the model is capable to reproduce realistically the life cycle of a convective cloud including the production of warm rain.A discussion of the role of advection in bin-microphysics models is presented and sensitivity tests were performed regarding the order of advection. The results show that, although the global characteristics of all simulated clouds were similar, significant differences occur with respect to their microstructure, particularly close to the cloud edges, when the order of the advective scheme changes. The conclusion is that intermediate-order advection schemes can indeed be used in cloud-resolving simulations, as far only as the gross characteristics of the cloud/cloud system are being investigated, but not poor, low-order schemes. On the other hand, the sensitivity with respect to the advection suggests that the evaluation of cloud phenomena that occur in fine-scales, such as entrainment and certain microphysical and radiational processes, must require the use of accurate, higher-order schemes.  相似文献   

林业科技是衢州林业发展的主动力     

浙江省衢州市林业局 《湿地科学与管理》2000,(1):51-53

<正> 衢州是浙江三大林区之一,人口238万,其中农业人口200万人,总面积88.47万公顷,林业用地62万公顷,有林地55.67万公顷,森林覆盖率65.4％。森林蓄积量1242万立方米,经济林10.67万公顷,竹林6万公顷,毛竹10700万株,林业生产在农业经济中占有重要的地位。 1985年衢州恢复地级市建制,辖四县一市一区。针对我市人口密度大,人均林地少,  相似文献   

Intrinsic correlation of galaxy shapes: implications for weak lensing measurements     

Alan Heavens  Alexandre Refregier  Catherine Heymans 《Monthly notices of the Royal Astronomical Society》2000,319(2):649-656

Weak gravitational lensing is now established as a powerful method to measure mass fluctuations in the universe. It relies on the measurement of small coherent distortions of the images of background galaxies. Even low-level correlations in the intrinsic shapes of galaxies could however produce a significant spurious lensing signal. These correlations are also interesting in their own right, since their detection would constrain models of galaxy formation. Using     haloes found in N -body simulations, we compute the correlation functions of the intrinsic ellipticity of spiral galaxies assuming that the disc is perpendicular to the angular momentum of the dark matter halo. We also consider a simple model for elliptical galaxies, in which the shape of the dark matter halo is assumed to be the same as that of the light. For deep lensing surveys with median redshifts ∼1, we find that intrinsic correlations of ∼10⁻⁴ on angular scales     are generally below the expected lensing signal, and contribute only a small fraction of the excess signals reported on these scales. On larger scales we find limits to the intrinsic correlation function at a level ∼10⁻⁵, which gives a (model-dependent) range of separations for which the intrinsic signal is about an order of magnitude below the ellipticity correlation function expected from weak lensing. Intrinsic correlations are thus negligible on these scales for dedicated weak lensing surveys. For wider but shallower surveys such as SuperCOSMOS, APM and SDSS, we cannot exclude the possibility that intrinsic correlations could dominate the lensing signal. We discuss how such surveys could be used to calibrate the importance of this effect, as well as study spin–spin correlations of spiral galaxies.  相似文献   

Detection of weak gravitational lensing by large-scale structure     

David J. Bacon  Alexandre R. Refregier  Richard S. Ellis 《Monthly notices of the Royal Astronomical Society》2000,318(2):625-640

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MIS 5/4 transition in a mountain environment: herpetofaunal assemblages from Cueva del Camino,central Spain     

Hugues‐Alexandre Blain  César Laplana  Paloma Sevilla  Juan Luis Arsuaga  Enrique Baquedano  Alfredo Pérez‐González 《Boreas: An International Journal of Quaternary Research》2014,43(1):107-120

The Cueva del Camino site (Pinilla del Valle, Madrid, Spain) is located in the upper valley of the Lozoya River in the Sierra de Guadarrama, a mountain range extending NE?SW within the Central Range System. Due to its location within a mountain range on the central Iberian Peninsula at an altitude of 1114 m a.s.l. and the numerical dating of its sediments, the palaeontological site of Cueva del Camino has proved a highly relevant location for studying the ecological changes linked to the climatic fluctuations at the end of Marine Isotope Stage (MIS) 5 and the beginning of MIS 4. Environmental reconstructions suggest a rather open, patchy landscape throughout the succession, with abundant evidence of dry meadows, scrublands and rocky habitats. The climate can be considered as generally warm, reaching mean annual temperatures (MATs) of up to 13.8°C (i.e. higher than today's by up to 2.9°C). Three cooler events can be seen throughout the succession as reflected by the presence of Rana iberica, Anguis fragilis and Coronella austriaca. The first of these events may correlate with MIS 5b; the second in the Central sector may correlate with the Stadial I pollen event occurring at the end of MIS 5a; and the third event, corresponding to the coldest MAT of the entire succession with MATs 0.9°C lower than today's, may correspond to the transition from MIS 5a to MIS 4. The evolution of mean annual precipitation (MAP) is characterized by warm periods, drier and cold periods, as well as wetter periods (up to +356 mm compared to today's MAP values), similar to what occurs today in the high‐elevation areas of the neighbouring mountains. Our study gives new quantitative estimations for the climatic fluctuations in mountain environments of central Spain at the MIS 5/4 transition and their associated ecological changes.  相似文献   

Hydrothermal overprint on Cenozoic sediments in the Quadrilátero Ferrífero of Minas Gerais: implications for precious metals in cratonic terrains     

Alexandre Raphael Cabral  Nikola Koglin 《地学学报》2014,26(2):111-119

Cenozoic sediments deposited in graben‐like basins in the Quadrilátero Ferrífero, southern São Francisco craton, Brazil, have anomalous contents of Hg and Sb. Two localities have been studied: the topaz deposit of Antônio Pereira, and the remains of the old opencast workings at Cata Preta, one of the earliest Au mines of Minas Gerais that dates back to about 1690. At Cata Preta, a brecciated wad‐like rock exhibits geochemical fingerprints that point to fractionation of Pt and Pd from Ag. This metal fractionation, reflected in the Au ingots produced in the region, genetically links Cata Preta to the near‐surface bonanza ore of Serra Pelada, which formed as a result of a Late‐Cretaceous hydrothermal overprint in the Amazon craton. Here, we propose that anorogenic hydrothermal activity in cratonic terrains prepared the ground for the enrichment in precious metals that gave rise to two of the most important Au rushes in Brazilian history.  相似文献   

Erratum to: Australian east coast rainfall decline related to large scale climate drivers     

Milton Samuel Speer  Lance M. Leslie  Alexandre O. Fierro 《Climate Dynamics》2011,36(7-8):1431-1434

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Metals in the Aquatic Environment—Interactions and Implications for the Speciation and Bioavailability: A Critical Overview     

Rute?F.?DomingosEmail author  Alexandre?Gélabert  Sara?Carreira  Ana?Cordeiro  Yann?Sivry  Marc?F.?Benedetti 《Aquatic Geochemistry》2015,21(2-4):231-257

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Fluid-inclusion microthermometry and the Zr-in-rutile thermometer for hydrothermal rutile     

Alexandre Raphael Cabral  Francisco Javier Rios  Lucilia Aparecida Ramos de Oliveira  Francisco Robério de Abreu  Bernd Lehmann  Thomas Zack  František Laufek 《International Journal of Earth Sciences》2015,104(2):513-519

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Moisture recycling and the maximum of precipitation in spring in the Iberian Peninsula     

Alexandre Rios-Entenza  Gonzalo Miguez-Macho 《Climate Dynamics》2014,42(11-12):3207-3231

In the semiarid interior of the Iberian Peninsula, the topographic insulation from the surrounding seas promotes the role of internal sources of moisture and water recycling in the rainfall regime. In inland Iberia, the annual cycle of precipitation often has a distinctive peak in the springtime, when evapotranspiration (ET) is the highest, in contrast to the coastal areas, where it is more closely related to the external moisture availability and synoptic forcing, with a maximum in winter-autumn and a pronounced minimum in the summer. In this work we investigate the role of land surface water fluxes in the intensification of the hydrological cycle in the Iberian spring. We used data from 5 km resolution WRF-ARW model simulations over the Iberian Peninsula for eleven months of May (2000–2010). To bring out the effect of ET fluxes, we conducted experiments where ET water over land was removed from the system. Our findings indicate that the impact of ET on precipitation is on average very large (37 % increase). The impact is particularly strong in the interior north and northeast areas where the observed annual rainfall cycle has a peak in May, suggesting that the role of surface water fluxes is very important there. To investigate whether this role is as a water source or to amplify precipitation dynamics, we computed the recycling ratio analytically from the model data. In addition, we developed a procedure to quantify the amplification impact by comparing the recycling ratio and the relative change in precipitation between control and experiments with ET removed. Results show that the role of surface water fluxes on precipitation depends on large-scale forcing and moisture advection. When the synoptic forcing and moisture advection are strong, such as in fronts associated to Atlantic storms, the impact of ET fluxes is small. When there is potential for convection, as is commonly the case of late spring in the Iberian Peninsula, ET fluxes have a significant impact. Surface moisture fluxes moisten the boundary layer and increase moist static energy, strengthening convective processes, and their role goes from being a primary water source for precipitation (recycling) to have mostly an amplification effect as external moisture availability increases. Our findings show that for the eleven simulated May cases over the Iberian Peninsula, the role of ET fluxes in activating recycling is important and explains 27–58 % of their total impact on precipitation, depending on the method used to calculate the recycling ratio. This indicates that the complementary effect of ET on amplifying rainfall from external sources of moisture is comparable in magnitude to the recycling mechanism and important as well.  相似文献