Species-specific responses of late Miocene Discoaster spp. to enhanced biosilica productivity conditions in the equatorial Pacific and the Mediterranean     

Jan Backman  Isabella Raffi  Marina Ciummelli  Jack Baldauf 《Geo-Marine Letters》2013,33(4):285-298

Census data of a major Cenozoic calcareous nannofossil genus (Discoaster) have been acquired from Site U1338, located near the Equator in the eastern Pacific Ocean and drilled in 2009 during Integrated Ocean Drilling Program (IODP) Expedition 321. The investigated 147.53 m thick upper Miocene sediment sequence is primarily composed of biogenic carbonate and biogenic silica. Diatom biostratigraphic data were used to develop a revised biomagnetostratigraphic age model, resulting in more variable late Miocene sedimentation rates. Carbonate content variations mainly reflect dilution by biogenic silica production, although intense carbonate dissolution affects a few shorter intervals. Abundance variations of discoasters show no distinct correlation with either carbonate or biosilica contents. The two dominant Discoaster taxa are D. brouweri and D. variabilis, except for a 12 m thick interval where D. bellus outnumbers the sum of all other discoasters by a factor of 4.6. Data presented indicate that first D. hamatus and then D. berggrenii both evolved from D. bellus. Three unusual morphotypes, here referred to as Discoaster A, B and C, increase in relative abundance during episodes of enhanced biosilica production in the upper half of the investigated sequence (Messinian). Strikingly similar morphotypes have been observed previously in Messinian age sediments from the Mediterranean, characterized by alternating deposition of biogenic carbonate and biosilica. This suggests a species-specific response among some of the late Miocene discoasters to broader oceanographic and climatic forcing that promoted episodes of enhanced deposition of biogenic silica.  相似文献   

Migration of Chlorophenolic Compounds at the Chemical Waste Disposal Site at Alkali Lake, Oregon – 2. Contaminant Distributions, Transport, and Retardation     

Richard L. Johnson  Susan M. Brillante  Lome M. Isabella  James E. Houck  James F. Pankow 《Ground water》1985,23(5):652-666

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Assessing agricultural drought management strategies in the Northern Murray–Darling Basin     

Aitkenhead  Isabella  Kuleshov  Yuriy  Watkins  Andrew B.  Bhardwaj  Jessica  Asghari  Atifa 《Natural Hazards》2021,109(2):1425-1455

Natural Hazards - The Northern Murray–Darling Basin (MDB) is a key Australian agricultural region requiring efficient Agricultural Drought Management (ADM), focused on resilience. Although a...  相似文献   

Utilization of Satellite-based Digital Elevation Model (DEM) for Hydrologic Applications: A Review     

Syeda Maria Zaidi  Abolghasem Akbari  Jacqueline Isabella Gisen  Jamil Hasan Kazmi  Asif Gul  Ng Zone Fhong 《Journal of the Geological Society of India》2018,91(3):329-333

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Evaluating CMIP5 models using GPS radio occultation COSMIC temperature in UTLS region during 2006–2013: twenty-first century projection and trends     

P. Kishore  Ghouse Basha  M. Venkat Ratnam  Isabella Velicogna  T. B. M. J. Ouarda  D. Narayana Rao 《Climate Dynamics》2016,47(9-10):3253-3270

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Precipitation climatology over India: validation with observations and reanalysis datasets and spatial trends     

P. Kishore  S. Jyothi  Ghouse Basha  S. V. B. Rao  M. Rajeevan  Isabella Velicogna  Tyler C. Sutterley 《Climate Dynamics》2016,46(1-2):541-556

Changing rainfall patterns have significant effect on water resources, agriculture output in many countries, especially the country like India where the economy depends on rain-fed agriculture. Rainfall over India has large spatial as well as temporal variability. To understand the variability in rainfall, spatial–temporal analyses of rainfall have been studied by using 107 (1901–2007) years of daily gridded India Meteorological Department (IMD) rainfall datasets. Further, the validation of IMD precipitation data is carried out with different observational and different reanalysis datasets during the period from 1989 to 2007. The Global Precipitation Climatology Project data shows similar features as that of IMD with high degree of comparison, whereas Asian Precipitation-Highly-Resolved Observational Data Integration Towards Evaluation data show similar features but with large differences, especially over northwest, west coast and western Himalayas. Spatially, large deviation is observed in the interior peninsula during the monsoon season with National Aeronautics Space Administration-Modern Era Retrospective-analysis for Research and Applications (NASA-MERRA), pre-monsoon with Japanese 25 years Re Analysis (JRA-25), and post-monsoon with climate forecast system reanalysis (CFSR) reanalysis datasets. Among the reanalysis datasets, European Centre for Medium-Range Weather Forecasts Interim Re-Analysis (ERA-Interim) shows good comparison followed by CFSR, NASA-MERRA, and JRA-25. Further, for the first time, with high resolution and long-term IMD data, the spatial distribution of trends is estimated using robust regression analysis technique on the annual and seasonal rainfall data with respect to different regions of India. Significant positive and negative trends are noticed in the whole time series of data during the monsoon season. The northeast and west coast of the Indian region shows significant positive trends and negative trends over western Himalayas and north central Indian region.  相似文献   

Contribution of long-term hydrothermal experiments for understanding the smectite-to-chlorite conversion in geological environments     

Régine?Mosser-RuckEmail author  Isabella?Pignatelli  Franck?Bourdelle  Mustapha?Abdelmoula  Odile?Barres  Damien?Guillaume  Delphine?Charpentier  Davy?Rousset  Michel?Cathelineau  Nicolas?Michau 《Contributions to Mineralogy and Petrology》2016,171(11):97

The smectite-to-chlorite conversion is investigated through long-duration experiments (up to 9 years) conducted at 300 °C. The starting products were the Wyoming bentonite MX80 (79 % smectite), metallic iron and magnetite in contact with a Na–Ca chloride solution. The predominant minerals in the run products were an iron-rich chlorite (chamosite like) and interstratified clays interpreted to be chlorite/smectite and/or corrensite/smectite, accompanied by euhedral crystals of quartz, albite and zeolite. The formation of pure corrensite was not observed in the long-duration experiments. The conversion of smectite into chlorite over time appears to take place in several steps and through several successive mechanisms: a solid-state transformation, significant dissolution of the smectite and direct precipitation from the solution, which is over-saturated with respect to chlorite, allowing the formation of a chamosite-like mineral. The reaction mechanisms are confirmed by X-ray patterns and data obtained on the experimental solutions (pH, contents of Si, Mg, Na and Ca). Because of the availability of some nutrients in the solution, total dissolution of the starting smectite does not lead to 100 % crystallization of chlorite but to a mixture of two dominant clays: chamosite and interstratified chlorite/smectite and/or corrensite/smectite poor in smectite. The role of Fe/(Fe + Mg) in the experimental medium is highlighted by chemical data obtained on newly formed clay particles alongside previously published data. The newly formed iron-rich chlorite has the same composition as that predicted by the geothermometer for diagenetic to low-grade metamorphic conditions, and the quartz + Fe-chlorite + albite experimental assemblage in the 9-year experiment is close to that fixed by water–rock equilibrium.  相似文献   

Zonal jets and cyclone–anticyclone asymmetry in decaying rotating turbulence: laboratory experiments and numerical simulations     

Stefania Espa  Isabella Bordi  Thomas Frisius  Klaus Fraedrich  Antonio Cenedese  Alfonso Sutera 《地球物理与天体物理流体动力学》2013,107(6):557-573

The problem of zonal jet formation and cyclone–anticyclone asymmetry in decaying rotating turbulence is addressed using both laboratory experiments and numerical simulations with a high-resolution shallow water model in a spherical geometry. Experiments are performed at different Rossby and Froude numbers and applying a rigid wall as meridional boundary in the numerical scheme to mimic the experimental apparatus. The formation of a zonally banded flow pattern, i.e. meridionally confined easterly/westerly jets, has observed; both experimental and numerical results confirmed that this tendency is favoured by high-planetary vorticity gradients. Also, in the experiments characterized by large rotation speeds and small Rossby deformation radius, an initial symmetric distribution of relative vorticity is found to evolve towards a dominance of anticyclonic structures, indicating a breaking of the cyclone–anticyclone symmetry. This aspect has deepened by numerically analysing the sensitivity of the temporal variations of the asymmetry index with respect to the position of the meridional confinement as well as the effect of relaxing the divergence of the fluid (i.e. non-divergent case) to zero. Results suggested that experiments characterized by the higher rotation speed and the lower fluid thickness are better reproduced by a divergent model with a high-latitude meridional boundary.  相似文献   

Ground-based GPS measurements: time behavior from half-hour to years     

Isabella Bordi  Klaus Fraedrich  Alfonso Sutera  Xiuhua Zhu 《Theoretical and Applied Climatology》2014,115(3-4):615-625

Ground-based GPS and weather stations time series for the period 2010–2012 of precipitable water vapor (PWV), relative humidity (RH), and surface temperature (T) of half-hourly resolution are analyzed to demonstrate their value for dynamical analyses and weather forecasting. Three sample stations in the USA from the SoumiNet network are considered, which have rather continuous data for the last 3 years and a few missing values. Results for the three stations reveal the following features: (1) PWV time behavior is dominated by the annual cycle superimposed on high-frequency fluctuations with missing daily cycle, indicating a prevailing large-scale transport source of precipitable water at these sites; (2) RH is characterized by the daily cycle and high-frequency variability, while the annual cycle is missing; (3) T mainly varies following the annual and diurnal cycles; and (4) all variables show similar scaling properties of their variance spectra, S(f)?～?f ^–β , with a high-frequency regime of red noise type scaling (β?～?2) up to a day and long-term persistence beyond a week (β?～?0.5), with a week-long frequency interval of transition. Detrended fluctuation analysis of relative humidity indicates a clear long-term persistence scaling covering more than three decades. Implications of these findings on weather forecasting and climate modeling are discussed.  相似文献   

Spatial patterns and temporal trends of daily precipitation indices in Iran     

Tayeb Raziei  Jamal Daryabari  Isabella Bordi  Reza Modarres  Luis S. Pereira 《Climatic change》2014,124(1-2):239-253

Spatial patterns of daily precipitation indices and their temporal trends over Iran are investigated using the APHRODITE gridded daily precipitation dataset for the period 1961–2004. The performance and limitations of the gridded dataset are checked against observations at ten rain-gauge stations that are representative of different climates in Iran. Results suggest that the spatial patterns of the indices reflect the role of orography and sea neighborhoods in differentiating central-southern arid and semi-arid regions from northern and western mountainous humid areas. It is also found that western Iran is impacted by the most extreme daily precipitation events occurring in the country, though the number of rainy days has its maximum in the Caspian Sea region. The time series of precipitation indices is checked for long-term trends using the least squares method and Mann-Kendall test. The maximum daily precipitation per year shows upward trends in most of Iran, though being statistically significant only in western regions. In the same regions, upward trends are also observed in the number of wet days and in the accumulated precipitation and intensity during wet days. Conversely, the contribution of precipitation events below the 75th percentile to the annual total precipitation is decreasing with time, suggesting that extreme events are responsible for the upward trend observed in the total annual precipitation and in the other indices. This tendency towards more severe/extreme precipitation events, if confirmed by other datasets and further analyses with longer records, would require the implementation of adequate water resources management plans in western Iran aimed at mitigating the increasing risk of intense precipitation and associated flash floods and soil erosion.  相似文献