Brazilian Decimetric Array (Phase-I)     

H. S. Sawant  R. Ramesh  J. R. Cecatto  C. Faria  F. C. R. Fernandes  R. R. Rosa  M. C. Andrade  S. Stephany  L. B. T. Cividanes  C. A. I. Miranda  L. C. L. Botti  J. W. S. V. Boas  J. H. Saito  C. E. Moron  N. D. Mascarenhas  K. R. Subramanian  M. S. Sundararajan  E. Ebenezer  M. R. Sankararaman 《Solar physics》2007,242(1-2):213-220

An East – West, one-dimensional radio interferometer array consisting of five parabolic dish antennas has been set up at Cachoeira Paulista (longitude 45°0′20″ W, latitude 22°41′19″ S) for observations of the Sun and some of the strong sidereal sources by the Instituto Nacional de Pesquisas Espaciais (INPE), Brazil. This is Phase-I of the proposed Brazilian Decimetric Array and can be operated at any frequency in the range 1.2 – 1.7 GHz. The instrument has been in operation since November 2004 onwards at 1.6 GHz. The angular and temporal resolutions at this frequency are ∼3′ and 100 ms, respectively. Details of the array, analog/digital receiver system, and a preliminary East – West one-dimensional solar image at the 1.6 GHz are presented in this paper.  相似文献   

Quantifying water vulnerability: a multi-dimensional approach   总被引：2，自引：0，他引：2  

Caroline A. Sullivan 《Stochastic Environmental Research and Risk Assessment (SERRA)》2011,25(4):627-640

In today’s uncertain world, vulnerability of water supplies is of increasing concern. A number of factors influence this, ranging from physical conditions through to human management capacities. Across the Orange River Basin in southern Africa, these threats arise from overpopulation and farming pressure, with agrochemical and industrial runoff as well as harsh weather conditions giving rise to severe problems of erosion and land degradation. Under conditions of climate change, these threats are exacerbated, as temperature rises and water resources become more erratic. Since water is both an essential instrument of livelihood support and a crucial factor of production, there is a need to develop more effective mechanisms to identify those areas where its scarcity or poor management can bring about a slowdown in the development process. This urgency is heightened by the international commitment to the Millennium Development Goals (MDGs), supposedly to be reached by 2015. In addition to the MDGs, governments are also committed to the development of basin management plans for Integrated Water Resources Management (IWRM). This means that, in order to try to allocate water in an equitable and efficient way, better understanding is needed of all of the complexities of managing water across heterogeneous basins. It is now recognized that effective water management is much more dependent on effective governance than on hydrologic regimes. Ranging from traditional local customary norms and practices dating back through generations to the latest state-of-the-art science-based international agreements, water governance is a key to supporting the lives and livelihoods of local populations. Access to information is an essential feature of any of these approaches, and harmonization of data on water issues is long overdue. This paper provides an outline of an index-based methodology on which an assessment of water vulnerability can be made. In this approach, supply-driven vulnerability (from water systems) and the demand-driven vulnerability (from water users), are evaluated at the municipal scale. By combining these various dimensions together mathematically, a Water Vulnerability Index (WVI) can be generated.  相似文献   

Corrigendum to “Metal tissue levels in Steller sea lion (Eumetopias jubatus) pups” [Marine Pollution Bulletin 56 (2008) 1416-1421]     

Amie L. Holmes  Sandra S. Wise  Caroline E.C. Goertz  J. Lawrence Dunn  Tom Gelatt  Kathy Burek  Mary Bozza  Tongzhang Zheng  AbouEl-Makarim Aboueissa 《Marine pollution bulletin》2011,62(4):881-882

  相似文献   

A transitioning Arctic surface energy budget: the impacts of solar zenith angle, surface albedo and cloud radiative forcing     

Joseph Sedlar  Michael Tjernström  Thorsten Mauritsen  Matthew D. Shupe  Ian M. Brooks  P. Ola G. Persson  Cathryn E. Birch  Caroline Leck  Anders Sirevaag  Marcel Nicolaus 《Climate Dynamics》2011,37(7-8):1643-1660

Snow surface and sea-ice energy budgets were measured near 87.5°N during the Arctic Summer Cloud Ocean Study (ASCOS), from August to early September 2008. Surface temperature indicated four distinct temperature regimes, characterized by varying cloud, thermodynamic and solar properties. An initial warm, melt-season regime was interrupted by a 3-day cold regime where temperatures dropped from near zero to ?7°C. Subsequently mean energy budget residuals remained small and near zero for 1 week until once again temperatures dropped rapidly and the energy budget residuals became negative. Energy budget transitions were dominated by the net radiative fluxes, largely controlled by the cloudiness. Variable heat, moisture and cloud distributions were associated with changing air-masses. Surface cloud radiative forcing, the net radiative effect of clouds on the surface relative to clear skies, is estimated. Shortwave cloud forcing ranged between ?50 W m^?2 and zero and varied significantly with surface albedo, solar zenith angle and cloud liquid water. Longwave cloud forcing was larger and generally ranged between 65 and 85 W m^?2, except when the cloud fraction was tenuous or contained little liquid water; thus the net effect of the clouds was to warm the surface. Both cold periods occurred under tenuous, or altogether absent, low-level clouds containing little liquid water, effectively reducing the cloud greenhouse effect. Freeze-up progression was enhanced by a combination of increasing solar zenith angles and surface albedo, while inhibited by a large, positive surface cloud forcing until a new air-mass with considerably less cloudiness advected over the experiment area.  相似文献   

The decomposition of windrowed, chipped logging slash and tree seedling response: A plant growth and nuclear magnetic resonance spectroscopy study     

Caroline M. Preston  Ronald J. SmernikRobert F. Powers  John G. McCollTherese M. McBeath 《Organic Geochemistry》2011,42(8):936-946

Forest management practices historically have reduced the mass of logging slash to facilitate planting and reduce fire risk. However, coarse woody debris (CWD) is considered an important component of unmanaged forests of western and coastal North America. An experiment was established in northern California using chipped logging slash concentrated in windrows to emulate large fallen logs to determine the effects of alternative logging residue treatments on soil fertility and the performance of planted ponderosa pine. Chip piles warmed faster than mineral soil, but upper regions dried quickly during the dry summers. Fourteen years after planting, growth response was positive, as seedling volume declined with distance from the windrows. After 6 and 10 years, chip samples showed little variation in total C, but total N was higher for 10-year samples, with slightly higher values at the base and for N-fertilized sections. Analysis by solid state ¹³C CPMAS NMR, verified by spin-counting and triplicate analysis showed only subtle differences among 10-year samples, with non-carbohydrate C slightly more abundant at the base of the piles and for windrows originally fertilized with N. However, proton spin relaxation editing (PSRE), based on differences in T_1H relaxation rates, was able to distinguish between C in relatively undecomposed lignocellulose (slowly relaxing) and more decomposed material and microbial residues (rapidly relaxing). The small differences between top and base, and between fertilized and control samples were concentrated in the rapidly relaxing component. Bulk composition of 10-year chip windrows was similar to CWD naturally decomposed by white-rot fungi, but PSRE offers a new approach to monitor spatially heterogeneous development of microsites more characteristic of brown rot.  相似文献   

Dual-frequency ADCPs measuring turbidity     

Frédéric Jourdin  Caroline Tessier  Pierre Le Hir  Romaric Verney  Michel Lunven  Sophie Loyer  André Lusven  Jean-François Filipot  Jérémy Lepesqueur 《Geo-Marine Letters》2014,34(4):381-397

A pair of self-contained acoustic Doppler current profilers (SC-ADCPs) operating with different frequencies were moored on a muddy sea bottom at about 20 m depth in the Bay of Vilaine off the French Atlantic coast. With their acoustic beams oriented upwards, the SC-ADCPs ensonified most of the water column. The results of several months of in situ recorded echo intensity data spanning 2 years (2003 to 2004) from the dual-frequency ADCPs are presented in this paper. The aim was to estimate suspended particle mass concentration and mean size. A concentration index CI is proposed for the estimation of particle concentration. Based on theory the CI—unlike the volume backscatter strength—does not depend on particle size. Compared with in situ optical data, the CI shows reasonable precision but not increased with respect to that of the highest-frequency backscatter strength. Concerning the mean particle size, despite a lack of quantitative validation with optical particle-size measurements, the method yielded a qualitative discrimination of mineral (small) and organic (large) particles. This supports the potential of dual-frequency ADCPs to quantitatively determine particle size. A cross-calibration of the transducers of each ADCP shows that a specific component of the precision of the backscatter strength measured by ADCP depends on the acoustic frequency, the cell thickness and the ensemble integration time. Based on these results, the use of two ADCPs operating with distinctly different frequencies (two octaves apart) or a single dual-frequency ADCP is recommended.  相似文献   

The surface radiation budget over South America in a set of regional climate models from the CLARIS-LPB project   总被引：1，自引：0，他引：1  

Natalia L. Pessacg  Silvina A. Solman  Patrick Samuelsson  Enrique Sanchez  José Marengo  Laurent Li  Armelle Reca C. Remedio  Rosmeri P. da Rocha  Caroline Mourão  Daniela Jacob 《Climate Dynamics》2014,43(5-6):1221-1239

The performance of seven regional climate models in simulating the radiation and heat fluxes at the surface over South America (SA) is evaluated. Sources of uncertainty and errors are identified. All simulations have been performed in the context of the CLARIS-LPB Project for the period 1990–2008 and are compared with the GEWEX-SRB, CRU, and GLDAS2 dataset and NCEP-NOAA reanalysis. Results showed that most of the models overestimate the net surface short-wave radiation over tropical SA and La Plata Basin and underestimate it over oceanic regions. Errors in the short-wave radiation are mainly associated with uncertainties in the representation of surface albedo and cloud fraction. For the net surface long-wave radiation, model biases are diverse. However, the ensemble mean showed a good agreement with the GEWEX-SRB dataset due to the compensation of individual model biases. Errors in the net surface long-wave radiation can be explained, in a large proportion, by errors in cloud fraction. For some particular models, errors in temperature also contribute to errors in the net long-wave radiation. Analysis of the annual cycle of each component of the energy budget indicates that the RCMs reproduce generally well the main characteristics of the short- and long-wave radiations in terms of timing and amplitude. However, a large spread among models over tropical SA is apparent. The annual cycle of the sensible heat flux showed a strong overestimation in comparison with the reanalysis and GLDAS2 dataset. For the latent heat flux, strong differences between the reanalysis and GLDAS2 are calculated particularly over tropical SA.  相似文献   

Effects of helical flow in one‐dimensional modelling of sediment distribution at river bifurcations     

Caroline F. van der Mark  Erik Mosselman 《地球表面变化过程与地形》2013,38(5):502-511

Complex flow processes at river bifurcations and the influence of the layout of a bifurcation make it difficult to predict sediment distribution over the downstream branches in case bedload transport dominates. In one‐dimensional models we need a nodal point relationship that prescribes the distribution of sediment over the downstream branches. We have identified which factors need to be included in such a relationship for the division of bedload transport at bifurcations. Next, irrotational flow theory for idealized geometries has been used to derive a simple physics‐based nodal point relationship that accounts for the effects of helical flow in the situation that a channel takes off under an angle from a straight main channel. This first step towards a complete nodal point relationship is applicable to bedload transport situations if the flow is clearly curved and if there is no pronounced bed topography. The relationship has been tested against data from a unique set of laboratory measurements, numerical data and data from a scale model of the Rhine bifurcation at Pannerden in the Netherlands. We find that the derived model yields a reasonable prediction of the sediment division over the downstream branches, and yields better predictions than the Wang et al. model for the situation considered. Considering the relative complexity and limited accuracy of the nodal point relationship for the effect of helical flow alone, however, we conclude thatderiving a practical physics‐based 1‐D relationship including all relevant processes is not feasible. We therefore recommend 2‐D or 3‐D modelling for all cases in general where morphological evolution depends on the division of bedload transport at bifurcations. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Numerical modelling of morphodynamics—Vilaine Estuary   总被引：1，自引：0，他引：1  

Hans Jacob Vested  Caroline Tessier  Bo Brahtz Christensen  Evelyne Goubert 《Ocean Dynamics》2013,63(4):423-446

The main objective of this paper is to develop a method to simulate long-term morphodynamics of estuaries dominated by fine sediments, which are subject to both tidal flow and meteorologically induced variations in freshwater run-off and wave conditions. The method is tested on the Vilaine Estuary located in South Brittany, France. The estuary is subject to a meso–macrotidal regime. The semi-diurnal tidal range varies from around 2.5 to 5 m at neap and spring, respectively. The freshwater input is controlled by a dam located approximately 8 km from the mouth of the estuary. Sediments are characterised as mostly fines, but more sandy areas are also found. The morphology of the estuary is highly influenced by the dam. It is very dynamic and changes in a complicated manner with the run-off from the dam, the tide and the wave forcing at the mouth of the estuary. Extensive hydrodynamic and sediment field data have been collected in the past and provide a solid scientific basis for studying the estuary. Based on a conceptual understanding of the morphodynamics, a numerical morphological model with coupled hydrodynamic, surface wave and sediment transport models is formulated. The numerical models are calibrated to reproduce sediment concentrations, tidal flat altimetry and overall sediment fluxes. Scaling factors are applied to a reference year to form quasi-realistic hydrodynamic forcing and river run-off, which allow for the simulations to be extended to other years. The simulation results are compared with observed bathymetric changes in the estuary during the period 1998–2005. The models and scaling factors are applied to predict the morphological development over a time scale of up to 10 years. The influence of the initial conditions and the sequence of external hydrodynamic forcing, with respect to the morphodynamic response of the estuary, are discussed.  相似文献   

Transition zone structure under a stationary hot spot: Cape Verde     

George Helffrich  Bruno Faria  João F.B.D. Fonseca  Alexandra Lodge  Satoshi Kaneshima 《Earth and Planetary Science Letters》2010,289(1-2):156-161

We report on a two-year seismic deployment in the Cape Verde Islands, one goal of which was to study the upper mantle to determine its structure under a hot spot that is stationary in the hot spot reference frame. We find from analysis of P-to-S receiver functions estimated from broadband seismic recordings that, within uncertainty, the time separation between the 410 and 660 km discontinuities is normal compared to radial earth models. Thus, to exist, even stationary hot spots do not require vertical thermal anomalies from deep melting sources anchored in the lower mantle or at the core–mantle boundary or their anomalies are narrower than ～ 250 km in the upper mantle.  相似文献