Mediterranean warm-core cyclones in a warmer world     

Kevin Walsh  Filippo Giorgi  Erika Coppola 《Climate Dynamics》2014,42(3-4):1053-1066

Regional climate model projections over the Mediterranean region are analysed for the presence of intense, warm-core lows that share some of the characteristics of tropical cyclones. The results indicate that the number of such systems decreases in a warmer world, particularly in winter. Comparison of the simulated numbers to changes in relevant climate diagnostics suggests that numbers decrease due to an increasingly hostile environment for storm formation, combined with a general poleward shift in the incidence of wintertime lows over western Europe.  相似文献   

Climate change impact on precipitation for the Amazon and La Plata basins   总被引：2，自引：0，他引：2  

Marta Llopart  Erika Coppola  Filippo Giorgi  Rosmeri P. da Rocha  Santiago V. Cuadra 《Climatic change》2014,125(1):111-125

We analyze the local and remote impacts of climate change on the hydroclimate of the Amazon and La Plata basins of South America (SA) in an ensemble of four 21st century projections (1970–2100, RCP8.5 scenario) with the regional climate model RegCM4 driven by the HadGEM, GFDL and MPI global climate models (GCMs) over the SA CORDEX domain. Two RegCM4 configurations are used, one employing the CLM land surface and the Emanuel convective schemes, and one using the BATS land surface and Grell (over land) convection schemes. First, we find considerable sensitivity of the precipitation change signal to both the driving GCM and the RegCM4 physics schemes (with the latter even greater than the first), highlighting the pronounced uncertainty of regional projections over the region. However, some improvements in the simulation of the annual cycle of precipitation over the Amazon and La Plata basins is found when using RegCM4, and some consistent change signals across the experiments are found. One is a tendency towards an extension of the dry season over central SA deriving from a late onset and an early retreat of the SA monsoon. The second is a dipolar response consisting of reduced precipitation over the broad Amazon and Central Brazil region and increased precipitation over the La Plata basin and central Argentina. An analysis of the relative influence on the change signal of local soil-moisture feedbacks and remote effects of Sea Surface Temperature (SST) over the Niño 3.4 region indicates that the former is prevalent over the Amazon basin while the latter dominates over the La Plata Basin. Also, the soil moisture feedback has a larger role in RegCM4 than in the GCMs.  相似文献   

Insight into the development of a carbonate platform through a multi-disciplinary approach: a case study from the Upper Devonian slope deposits of Mount Freikofel (Carnic Alps,Austria/Italy)     

Damien Pas  Anne-Christine Da Silva  Thomas Suttner  Erika Kido  Pierre Bultynck  Monica Pondrelli  Carlo Corradini  David De Vleeschouwer  Claudia Dojen  Frédéric Boulvain 《International Journal of Earth Sciences》2014,103(2):519-538

The development and behavior of million year-scaled depositional sequences recorded within Palaeozoic carbonate platform has remained poorly examined. Therefore, the understanding of palaeoenvironmental changes that occur in geological past is still limited. We herein undertake a multi-disciplinary approach (sedimentology, conodont biostratigraphy, magnetic susceptibility (MS), and geochemistry) of a long-term succession in the Carnic Alps, which offers new insights into the peculiar evolution of one of the best example of Palaeozoic carbonate platform in Europe. The Freikofel section, located in the central part of the Carnic Alps, represents an outstanding succession in a fore-reef setting, extending from the Latest Givetian (indet. falsiovalis conodont zones) to the Early Famennian (Lower crepida conodont zone). Sedimentological analysis allowed to propose a sedimentary model dominated by distal slope and fore-reef-slope deposits. The most distal setting is characterized by an autochthonous pelagic sedimentation showing local occurrence of thin-bedded turbiditic deposits. In the fore-reef slope, in a more proximal setting, there is an accumulation of various autochthonous and allochthonous fine- to coarse-grained sediments originated from the interplay of gravity-flow currents derived from the shallow-water and deepwater area. The temporal evolution of microfacies in the Freikofel section evolves in two main steps corresponding to the Freikofel (Unit 1) and the Pal (Unit 2) limestones. Distal slope to fore-reef lithologies and associate changes are from base to top of the section: (U1) thick bedded litho- and bioclastic breccia beds with local fining upward sequence and fine-grained mudstone intercalations corresponding, in the fore-reef setting, to the dismantlement of the Eifelian–Frasnian carbonate platform during the Early to Late Frasnian time (falsiovalis to rhenana superzones) with one of the causes being the Late Givetian major rift pulse; (U2) occurrence of thin-bedded red nodular and cephalopod-bearing limestones with local lithoclastic grainstone intercalations corresponding to a significant deepening of the area and the progressive withdrawal of sedimentary influxes toward the basin, in relation with Late Frasnian sea-level rise. MS and geochemical analyses were also performed along the Freikofel section and demonstrate the inherent parallel link existing between variation in MS values and proxy for terrestrial input. Interpretation of MS in terms of palaeoenvironmental processes reflects that even though distality remains the major parameter influencing MS values, carbonate production and water agitation also play an important role.  相似文献   

Projected seasonal mean summer monsoon over India and adjoining regions for the twenty-first century     

Sushil K. Dash  Saroj K. Mishra  Kanhu C. Pattnayak  Ashu Mamgain  Laura Mariotti  Erika Coppola  Filippo Giorgi  Graziano Giuliani 《Theoretical and Applied Climatology》2015,122(3-4):581-593

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Potentials and constraints of different types of soil moisture observations for flood simulations in headwater catchments     

Axel Bronstert  Benjamin Creutzfeldt  Thomas Graeff  Irena Hajnsek  Maik Heistermann  Sibylle Itzerott  Thomas Jagdhuber  David Kneis  Erika Lück  Dominik Reusser  Erwin Zehe 《Natural Hazards》2012,60(3):879-914

Flood generation in mountainous headwater catchments is governed by rainfall intensities, by the spatial distribution of rainfall and by the state of the catchment prior to the rainfall, e.g. by the spatial pattern of the soil moisture, groundwater conditions and possibly snow. The work presented here explores the limits and potentials of measuring soil moisture with different methods and in different scales and their potential use for flood simulation. These measurements were obtained in 2007 and 2008 within a comprehensive multi-scale experiment in the Weisseritz headwater catchment in the Ore-Mountains, Germany. The following technologies have been applied jointly thermogravimetric method, frequency domain reflectometry (FDR) sensors, spatial time domain reflectometry (STDR) cluster, ground-penetrating radar (GPR), airborne polarimetric synthetic aperture radar (polarimetric SAR) and advanced synthetic aperture radar (ASAR) based on the satellite Envisat. We present exemplary soil measurement results, with spatial scales ranging from point scale, via hillslope and field scale, to the catchment scale. Only the spatial TDR cluster was able to record continuous data. The other methods are limited to the date of over-flights (airplane and satellite) or measurement campaigns on the ground. For possible use in flood simulation, the observation of soil moisture at multiple scales has to be combined with suitable hydrological modelling, using the hydrological model WaSiM-ETH. Therefore, several simulation experiments have been conducted in order to test both the usability of the recorded soil moisture data and the suitability of a distributed hydrological model to make use of this information. The measurement results show that airborne-based and satellite-based systems in particular provide information on the near-surface spatial distribution. However, there are still a variety of limitations, such as the need for parallel ground measurements (Envisat ASAR), uncertainties in polarimetric decomposition techniques (polarimetric SAR), very limited information from remote sensing methods about vegetated surfaces and the non-availability of continuous measurements. The model experiments showed the importance of soil moisture as an initial condition for physically based flood modelling. However, the observed moisture data reflect the surface or near-surface soil moisture only. Hence, only saturated overland flow might be related to these data. Other flood generation processes influenced by catchment wetness in the subsurface such as subsurface storm flow or quick groundwater drainage cannot be assessed by these data. One has to acknowledge that, in spite of innovative measuring techniques on all spatial scales, soil moisture data for entire vegetated catchments are still today not operationally available. Therefore, observations of soil moisture should primarily be used to improve the quality of continuous, distributed hydrological catchment models that simulate the spatial distribution of moisture internally. Thus, when and where soil moisture data are available, they should be compared with their simulated equivalents in order to improve the parameter estimates and possibly the structure of the hydrological model.  相似文献   

Spatiotemporal analysis of the atmospheric and surface urban heat islands of the Metropolitan Area of Toluca,Mexico     

Erika Rivera  Xanat Antonio-Némiga  Gabriel Origel-Gutiérrez  Pablo Sarricolea  Salvador Adame-Martínez 《Environmental Earth Sciences》2017,76(5):225

The dynamic of consolidation of urban areas in Latin America has allowed that almost 80% of the population concentrates in cities; this has produced changes in land covers and modified regional climate, propitiating the appearance of urban heat islands. The Metropolitan Area of Toluca, State of Mexico, Mexico, holds the fifth national place in population size and experiences this process, because of this, the objective is to analyze and compare the spatiotemporal characteristics of the atmospheric urban heat island obtained from data gathered from 12 urban and rural weather stations with the surface urban heat island obtained from the digital processing of four Landsat 8 images. Results show the year-round presence of night-time atmospheric urban heat islands, which reach a peak in autumn (up to 6 °C). Daytime atmospheric urban heat islands occur in summer and autumn with a maximum intensity of 4 °C. For their part, surface urban heat islands occur in spring, summer and autumn and reach maximums of 19 °C in intensity. A strong correlation was found between wetness and surface temperature (coefficient of determination, 0.8) in spring and winter. Soil wetness directly impacts the formation of weak urban heat islands in dry season, and intense ones in wet season, while the green areas and the winds affect the spatial distribution of the same.  相似文献   

Thermal conductivity measurements of coarse-grained gravel materials using a hollow cylindrical sensor     

Norbert I. Kömle  Erika S. Hütter  Wenjie J. Feng 《Acta Geotechnica》2010,5(4):211-223

We report on new results for the thermal conductivity of granular materials, in particular large-grained gravels. For these measurements, a cylindrical-shaped heated sensor was developed and used, which allows to include gravels with grain sizes in the several centimeter size range into the investigation. Such materials are, among else, important as construction materials for road and railway embankments. Measurements were done at different gas pressure levels (from normal atmospheric level down to the millibar range) and for dry and wet conditions. The results of the low pressure measurements may become relevant in view of possible applications on other planetary bodies, like at the surface of the planet Mars, which will be explored in the coming decade by in situ geotechnical methods.  相似文献   

Barium uptake and adsorption in diatoms     

Erika Sternberg  Degui Tang  Tung-Yuan Ho  François M.M. Morel 《Geochimica et cosmochimica acta》2005,69(11):2745-2752

Using trace metal-defined culture conditions, we measured the cellular barium concentration in cultures of the diatom Thalassiosira weissflogii. In cultures with low Fe concentration, at a typical surface seawater Ba concentration of 35 to 40 nmol/L, the cellular Ba was 0.5 μmol/mol P (∼0.04 μg/g dw), much below all previously published values for phytoplankton. When the Fe concentration in the growth medium was increased, the measured “cellular” Ba increased proportionally to the particulate Fe. Under conditions of ferric hydroxide precipitation, similar particulate Ba concentrations were measured in the absence and the presence of cells for a given concentration of particulate Fe. Thus, the bulk of the particulate Ba in such experiments was not truly intracellular but adsorbed on precipitated Fe hydroxides associated with the cell surface. A similar mechanism likely explains the high cellular Ba concentrations reported by previous investigators who utilized relatively high ratios of Fe to EDTA concentrations in the growth medium, resulting in Fe precipitation. On the basis of our results, it seems highly unlikely that intracellular uptake by living phytoplankton explains the vertical flux of Ba in oceanic waters. But the adsorption of Ba on Fe hydroxides that is seen in laboratory experiments must also occur in the oceans and contribute to Ba transport in the upper part of the water column. To be significant, however, such a mechanism would require that the particles that transport Ba out of the surface have a markedly lower Ba/Fe ratio than is measured in the average suspended material.  相似文献   

Processing, modelling and predicting time-lapse effects of overpressured fluid-injection in a fractured reservoir   总被引：2，自引：0，他引：2  

Erika Angerer  Stuart Crampin  Xiang-Yang Li  Thomas L. Davis 《Geophysical Journal International》2002,149(2):267-280

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Rates, patterns, and impacts ofPhragmites australis expansion and effects of experimentalPhragmites control on vegetation, macroinvertebrates, and fish within tidelands of the lower Connecticut River     

R. Scott Warren  Paul E. Fell  Jonna L. Grimsby  Erika L. Buck  G. Chris Rilling  Rachel A. Fertik 《Estuaries and Coasts》2001,24(1):90-107

Phragmites expansion rates (linear at 1–3% yr⁻¹) and impacts of this expansion on high marsh macroinvertebrates, aboveground production, and litter decomposition fromPhragmites and other marsh graminoids were studied along a polyhaline to oligohaline gradient. These parameters, and fish use of creeks and high marsh, were also studied inPhragmites control sites (herbicide, mowing, and combined herbicide/mow treatments).Phragmites clones established without obvious site preferences on oligohaline marshes, expanding radially. At higher salinities,Phragmites preferentially colonized creekbank levees and disturbed upland borders, then expanded into the central marsh. Hydroperiods, but not salinities or water table, distinguishedPhragmites-dominated transects. Pooled samples ofPhragmites leaves, stems, and flowers decompose more slowly than other marsh angiosperms;Phragmites leaves alone decompose as or more rapidly than those of cattail. AbovegroundPhragmites production was 1,300 to 2,400 g m⁻² (about 23% of this as leaves), versus 600–800 g m⁻² for polyhaline to mesohaline meadow and 1,300 g m⁻² for oligohaline cattail-sedge marsh. Macroinvertebrates appear largely unaffected byPhragmites expansion or control efforts; distribution and densities are unrelated to elevation or hydroperiod, but densities are positively related to litter cover. Dominant fish captured leaving flooded marsh wereFundulus heteroclitus andAnguilla rostrata; both preyed heavily on marsh macroinvertebrates.A. rostrata andMorone americana tended to be more common inPhragmites, but otherwise there were no major differences in use patterns betweenPhragmites and brackish meadow vegetation. SAV and macroalgal cover were markedly lower within aPhragmites-dominated creek versus one withSpartina-dominated banks. The same fish species assemblage was trapped in both plus a third within the herbicide/mow treatment. Fish biomass was greatest from theSpartina creek and lowest from thePhragmites creek, reflecting abundances ofF. heteroclitus. Mowing depressedPhragmites aboveground production and increased stem density, but was ineffective for control.Phragmites, Spartina patens, andJuncus gerardii frequencies after herbicide-only treatment were 0.53-0.21; total live cover was <8% with a heavy litter and dense standing dead stems. After two growing seasonsAgrostis stolonifera/S. patens/J. gerardii brackish meadow characterized most of the herbicide/mow treatment area;Phragmites frequency here was 0.53, contributing 3% cover. Both values more than doubled after four years; a single treatment is ineffective for long-termPhragmites control.  相似文献