Comparative Analysis of Phytoplankton Composition and Abundance over a Two-Decade Period at the Land–Ocean Boundary of a Tropical Mangrove Ecosystem     

Haimanti Biswas  Mitali Dey  Dipnarayan Ganguly  Tarun K. De  Sandip Ghosh  Tapan K. Jana 《Estuaries and Coasts》2010,33(2):384-394

Inter-annual variations of phytoplankton abundance and community organization were observed over a two-decade period along with the ancillary parameters at the land–ocean boundary associated with the Sundarban mangrove forest (21°32′ and 22°40′ N and 88°05′ and 89° E), along the NE Coast of the Bay of Bengal. The number of definable Bacillariophyceae species exceeded Dinophyceae taxa, and the total number of bloom-forming species declined from a maximum of ten in 2000 and a minimum of two in 2007. Blooms of the diatom Coscinodiscus radiatus were common in 2000 and 2007. Tide cycles and the onset of the monsoon season played important roles in diurnal and seasonal variability of phytoplankton. Phytoplankton biovolume showed seasonality, with the highest levels during post-monsoon periods and lowest levels during the monsoon period. Phytoplankton abundance was correlated to rainfall patterns, which may be altered by long-term changes in climate.  相似文献   

Alpine paleostress reconstruction and active faulting in Western Iberia     

Loreto Antón  Alfonso Muñoz-Martin  Gerardo De Vicente 《Central European Journal of Geosciences》2010,2(2):152-164

The study of intraplate tectonics is crucial for understanding the deformation within plates, far from active plate boundaries and associated stress transmission to the plate interiors. This paper examines the tectonic evolution of the Variscan basement at the western margin of the Cenozoic Duero basin. Located east of the Vilariça Fault System in NW Iberia, this intraplate zone is a relatively flat but elevated area with an intense NNE-SSW trending fault system and associated moderate seismicity. Although the area has played an important role in the Duero basin configuration, its Alpine to present-day tectonic evolution has not been well constrained. In order to characterize the successive paleostress fields, 1428 pairs of fault-striae were measured at 56 sites and two focal mechanisms were used. Stress inversion methods have been applied to analyze paleostress regimes. Results show the existence of three dominant maximum horizontal stress (Shmax) trends: N-S, NE-SW and E-W. Relative and absolute dating of the activated faults for each Shmax shows that the clearly predominant N-S paleostress field in the zone has been active since the Oligocene up to the present day; while a NE-SW stress field is found to have been active during the Cretaceous and an older E-W paleostress field was active in the earlier Alpine cycle (Late Triassic).  相似文献   

An integrated evaluation of thirteen modelling solutions for the generation of hourly values of air relative humidity     

Simone Bregaglio  Marcello Donatelli  Roberto Confalonieri  Marco Acutis  Simone Orlandini 《Theoretical and Applied Climatology》2010,102(3-4):429-438

The availability of hourly air relative humidity (HARH) data is a key requirement for the estimation of epidemic dynamics of plant fungal pathogens, in particular for the simulation of both the germination of the spores and the infection process. Most of the existing epidemic forecasting models require these data as input directly or indirectly, in the latter case for the estimation of leaf wetness duration. In many cases, HARH must be generated because it is not available in historical series and when there is the need to simulate epidemics either on a wide scale or with different climate scenarios. Thirteen modelling solutions (MS) for the generation of this variable were evaluated, with different input requirements and alternative approaches, on a large dataset including several sites and years. A composite indicator was developed using fuzzy logic to compare and to evaluate the performances of the models. The indicator consists of four modules: Accuracy, Correlation, Pattern and Robustness. Results showed that when available, daily maximum and minimum air relative humidity data substantially improved the estimation of HARH. When such data are not available, the choice of the MS is crucial, given the difference in predicting skills obtained during the analysis, which allowed a clear detection of the best performing MS. This study represents the first step of the creation of a robust modelling chain coupling the MS for the generation of HARH and disease forecasting models, including the systematic validation of each step of the simulation.  相似文献   

Intercomparison and analyses of the climatology of the West African Monsoon in the West African Monsoon Modeling and Evaluation project (WAMME) first model intercomparison experiment   总被引：3，自引：3，他引：0  

Yongkang Xue  Fernando De Sales  W. K.-M. Lau  Aaron Boone  Jinming Feng  Paul Dirmeyer  Zhichang Guo  Kyu-Myong Kim  Akio Kitoh  Vadlamani Kumar  Isabelle Poccard-Leclercq  Natalie Mahowald  Wilfran Moufouma-Okia  Phillip Pegion  David P. Rowell  Jae Schemm  Siegfried D. Schubert  Andrea Sealy  Wassila M. Thiaw  Augustin Vintzileos  Steven F. Williams  Man-Li C. Wu 《Climate Dynamics》2010,35(1):3-27

This paper briefly presents the West African Monsoon (WAM) Modeling and Evaluation Project (WAMME) and evaluates WAMME general circulation models’ (GCM) performances in simulating variability of WAM precipitation, surface temperature, and major circulation features at seasonal and intraseasonal scales in the first WAMME experiment. The analyses indicate that models with specified sea surface temperature generally have reasonable simulations of the pattern of spatial distribution of WAM seasonal mean precipitation and surface temperature as well as the averaged zonal wind in latitude-height cross-section and low level circulation. But there are large differences among models in simulating spatial correlation, intensity, and variance of precipitation compared with observations. Furthermore, the majority of models fail to produce proper intensities of the African Easterly Jet (AEJ) and the tropical easterly jet. AMMA Land Surface Model Intercomparison Project (ALMIP) data are used to analyze the association between simulated surface processes and the WAM and to investigate the WAM mechanism. It has been identified that the spatial distributions of surface sensible heat flux, surface temperature, and moisture convergence are closely associated with the simulated spatial distribution of precipitation; while surface latent heat flux is closely associated with the AEJ and contributes to divergence in AEJ simulation. Common empirical orthogonal functions (CEOF) analysis is applied to characterize the WAM precipitation evolution and has identified a major WAM precipitation mode and two temperature modes (Sahara mode and Sahel mode). Results indicate that the WAMME models produce reasonable temporal evolutions of major CEOF modes but have deficiencies/uncertainties in producing variances explained by major modes. Furthermore, the CEOF analysis shows that WAM precipitation evolution is closely related to the enhanced Sahara mode and the weakened Sahel mode, supporting the evidence revealed in the analysis using ALMIP data. An analysis of variability of CEOF modes suggests that the Sahara mode leads the WAM evolution, and divergence in simulating this mode contributes to discrepancies in the precipitation simulation.  相似文献   

Modelling and interpreting the dependence of clustering on the spectral energy distributions of galaxies     

Lan Wang  Cheng Li  Guinevere Kauffmann  Gabriella De Lucia 《Monthly notices of the Royal Astronomical Society》2007,377(4):1419-1430

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Preference of echo features for classification of seafloor sediments using neural networks     

Chanchal De  Bishwajit Chakraborty 《Marine Geophysical Researches》2010,31(3):215-221

Selection of a set of dominant echo features to classify seafloor sediments using a multilayer perceptron neural network is investigated at two acoustic frequencies (33 and 210 kHz). Several sets of inputs with different combinations of two, three, four, five, and six echo features are exploited with three-layer neural networks. The performances of the networks are analyzed to assess the most discriminating set of echo features for classification of seafloor sediments. The results of the overall average performances reveal that backscatter strength and time spread are the two most important echo features at 33 kHz, whereas backscatter strength has higher discriminating characteristics at 210 kHz for seafloor sediment classification. In addition, a set of four echo features consisting of backscatter strength, time-spread, statistical skewness, and Hausdroff dimension gives the highest success at both the acoustic frequencies.  相似文献   

Comparison of spectral and time domain calibration methods for precipitation‐discharge processes     

Jan J. Quets  Gabriëlle J. M. De Lannoy  Valentijn R. N. Pauwels 《水文研究》2010,24(8):1048-1062

Hydrological model parameter estimation is an important aspect in hydrologic modelling. Usually, parameters are estimated through an objective function minimization, quantifying the mismatch between the model results and the observations. The objective function choice has a large impact on the sensitivity analysis and calibration outcomes. In this study, it is assessed whether spectral objective functions can compete with an objective function in the time domain for optimization of the Soil and Water Assessment Tool (SWAT). Three empirical spectral objective functions were applied, based on matching (i) Fourier amplitude spectra, (ii) periodograms and (iii) Fourier series of simulated and observed discharge time series. It is shown that most sensitive parameters and their optimal values are distinct for different objective functions. The best results were found through calibration with an objective function based on the square difference between the simulated and observed discharge Fourier series coefficients. The potential strengths and weaknesses of using a spectral objective function as compared to utilising a time domain objective function are discussed. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Phase separation,fluid mixing,and origin of the greisens and potassic episyenite associated with the Água Boa pluton,Pitinga tin province,Amazonian Craton,Brazil     

Régis Munhoz Krás Borges  Raimundo Netuno Nobre Villas  Kazuo Fuzikawa  Roberto Dall’Agnol  Marcos Assunção Pimenta 《Journal of South American Earth Sciences》2009,27(2-3):161-183

Based on petrographical data, three types of greisen have been characterized at the western border of Água Boa pluton: siderophyllite–topaz–quartz greisen (greisen 1), fluorite–phengite–quartz greisen (greisen 2) and quartz–chlorite–phengite greisen (greisen 3). Episyenites were also identified.Two fluids of independent origin interacted with the same protolith – a hornblende-biotite alkali feldspar granite – and produced both the greisens and potassic episyenite: (1) an acid, low-salinity (4–12 wt.% NaCl eq.), F-rich, relatively hot (400–350 °C) reduced aqueous-carbonic fluid (CH₄–H₂O–NaCl–FeCl₂ ± KCl), which by immiscibility gave rise to fluid IA (aqueous) and IC (carbonic); and (2) a lower salinity (2–4 wt.% NaCl eq.) and temperature (200–150 °C) aqueous fluid (H₂O–NaCl), which was responsible for all dilution processes. Fluid 1 seems to have had a magmatic-hydrothermal origin, while fluid 2 is probably surface-derived (meteoric water?). An alkaline, F-poorer and diluted equivalent of fluid IA was interpreted to have caused the episyenitization of the granite host rock as well as the formation of phengite-rich greisen 3. The continuos interaction of this fluid with the potassic episyenite produced a moderate- to high-salinity (20–24 wt.% NaCl eq.), low-temperature (200–100 °C) fluid (H₂O–NaCl–CaCl₂ ± KCl), leading to the formation of chlorite-rich zone of greisen 3 and late silicification of potassic episyenite.In the greisen 1, decreasing F-activity and increasing oxygen fugacity, as the system cooled down, favored the formation of a topaz-rich inner zone, which grades into a siderophyllite-rich zone outwardly. Greisen 2 was formed under more oxidizing conditions by fluids poorer in F than those trapped in the siderophyllite-rich zone.The oxidation of aqueous-carbonic fluid took place at three distinct stages: (i) below the FMQ buffer; (ii) between the FMQ and NNO buffers; and (iii) above the NNO buffer.The dissolution cavities generated during the episyenitization process increased the permeability of the altered rocks, resulting in an increase of the fluid/rock ratios at the potassic episyenite and greisen 3 sites.All these fluids were trapped under pressure conditions of <1.0 kbar, representing shallow crustal levels and are consistent with those that have been estimated for the Pitinga tin–granites.The oxygen fugacity, F-activity gradients and salinity variations that occurred during the cooling of the hydrothermal system, in addition to differences in permeability, were important factors in the formation of distinct greisens. They not only controlled the fluid compositional changes, but also caused the cassiterite and sulfide precipitation at the greisen sites.  相似文献   

WMAP 3-yr data with Correlated Component Analysis: anomalous emission and impact of component separation on the CMB power spectrum     

A. Bonaldi  S. Ricciardi  S. Leach  F. Stivoli  C. Baccigalupi  G. De Zotti 《Monthly notices of the Royal Astronomical Society》2007,382(4):1791-1803

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Granites and their enclaves,developments in petrology, 3: J. Didier. Elsevier,Amsterdam-London-New York, 1973, 393 pp., Dfl. 100.00     

C.A.R. De Albuquerque 《Chemical Geology》1974,13(3):234-236

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