Petrogenesis and tectonic significance of Jurassic IAT magma types in the Hellenide ophiolites as deduced from the Rhodiani ophiolites (Pelagonian zone, Greece)   总被引：1，自引：0，他引：1  

Emilio Saccani  Adonis Photiades  Luigi Beccaluva   《Lithos》2008,104(1-4):71-84

The Rhodiani ophiolites are represented by two tectonically superimposed ophiolitic units: the “lower” Ultramafic unit and the “upper” Volcanic unit, both bearing calcareous sedimentary covers. The Ultramafic unit consists of mantle harzburgites with dunite pods and chromitite ores, and represents the typical mantle section of supra-subduction zone (SSZ) settings. The Volcanic unit is represented by a sheeted dyke complex overlain by a pillow and massive lava sequence, both including basalts, basaltic andesites, andesites, and dacites. Chemically, the Volcanic unit displays low-Ti affinity typical of island arc tholeiite (IAT) ophiolitic series from SSZ settings, having, as most distinctive chemical features, low Ti/V ratios (< 20) and depletion in high field strength elements and light rare earth elements.The rare earth element and incompatible element composition of the more primitive basaltic andesites from the Rhodiani ophiolites can be successfully reproduced with about 15% non-modal fractional melting of depleted lherzolites, which are very common in the Hellenide ophiolites. The calculated residua correspond to the depleted harzburgites found in the Rhodiani and Othrys ophiolites. Both field and chemical evidence suggest that the whole sequence of the Rhodiani Volcanic unit (from basalt to dacite) originated by low-pressure fractional crystallization under partially open-system conditions. The modelling of mantle source, melt generation, and mantle residua carried out in this paper provides new constraints for the tectono-magmatic evolution of the Mirdita–Pindos oceanic basin.  相似文献   

Shallow Water Bathymetry Derived from Green Wavelength Terrestrial Laser Scanner     

Theodore Panagou  Emmanouil Oikonomou  Adonis F. Velegrakis 《Marine Geodesy》2020,43(5):472-492

Abstract

Shallow water bathymetry has proved to be a challenging task for remote sensing applications. In this work, Green-Wavelength Terrestrial Laser Scanning (GWTLS) is employed to survey nearshore bathymetry under clear atmospheric and water conditions. First, the obtained seabed points were corrected for refraction and then geo-registration, and filtering processes were exerted to obtain an accurate bathymetric surface. Terrain analysis was performed with respect to a reference surface derived from classical surveying techniques. The overall analysis has shown that the best results stem from 35° to 50° incident angles, whereas for angles higher than 65° measurements are not acceptable, although for the same angle in front and close to the instrument accuracy is considered acceptable due to the high laser power. Also, high resolution micro-topography, shallower than 1?m water depth, was managed to be captured. Systematic experimental approaches are expected to improve the GWTLS technique to detect bathymetry, which is anticipated to assist in mapping very shallow foreshore, tidal, and deltaic environments, to contribute conceptual into developing hybrid observation systems for coastal monitoring, and also to be applied in various maritime applications.  相似文献   

High resolution simulations of January and July climate over the western Alpine region with a nested Regional Modeling system   总被引：1，自引：0，他引：1  

M. R. Marinucci  F. Giorgi  M. Beniston  M. Wild  P. Tschuck  A. Ohmura  A. Bernasconi 《Theoretical and Applied Climatology》1995,51(3):119-138

Summary High resolution January and July present day climatologies over the central-western Alpine region are simulated with a Regional Climate Model (RegCM) nested within a General Circulation Model (GCM). The RegCM was developed at the National Center for Atmospheric Research (NCAR) and is run at 20 km grid point spacing. The model is driven by output from a present day climate simulation performed with the GCM ECHAM3 of the Max Planck Institute for Meteorology (MPI) at T106 resolution (~ 120 km). Five January and July simulations are conducted with the nested RegCM and the results for surface air temperature and precipitation are compared with a gridded observed dataset and a dataset from 99 observing stations throughout the Swiss territory. The driving ECHAM3 simulation reproduces well the position of the northeastern Atlantic jet, but underestimates the jet intensity over the Mediterranean. Precipitation over the Alpine region in the ECHAM3 simulation is close to observed in January but lower than observed in July. Compared to the driving GCM, the nested RegCM produces more precipitation in both seasons, mostly as a result of the stronger model orographic forcing. Average RegCM temperature over the Swiss region is 2–3 degrees higher than observed, while average precipitation is within 30% of observed values. The spatial distribution of precipitation is in general agreement with available gridded observations and the model reproduces the observed elevation dependency of precipitation in the summer. In the winter the simulated elevation of maximum precipitation amounts is lower than observed. Precipitation frequencies are overestimated, while precipitation intensities show a reasonable agreement with observations, especially in the winter. Sensitivity experiments with different cumulus parameterizations, soil moisture initialization and model topography are discussed. Overall, the model performance at the high resolution used here did not deteriorate compared to previous lower resolution experiments.The National Center for Atmospheric Research is sponsored by the National Science Foundation.With 11 Figures  相似文献   

Global high resolution versus Limited Area Model climate change projections over Europe: quantifying confidence level from PRUDENCE results     

M. Déqué  R. G. Jones  M. Wild  F. Giorgi  J. H. Christensen  D. C. Hassell  P. L. Vidale  B. Rockel  D. Jacob  E. Kjellström  M. de. Castro  F. Kucharski  B. van den Hurk 《Climate Dynamics》2005,25(6):653-670

Four high resolution atmospheric general circulation models (GCMs) have been integrated with the standard forcings of the PRUDENCE experiment: IPCC-SRES A2 radiative forcing and Hadley Centre sea surface temperature and sea-ice extent. The response over Europe, calculated as the difference between the 2071–2100 and the 1961–1990 means is compared with the same diagnostic obtained with nine Regional Climate Models (RCM) all driven by the Hadley Centre atmospheric GCM. The seasonal mean response for 2m temperature and precipitation is investigated. For temperature, GCMs and RCMs behave similarly, except that GCMs exhibit a larger spread. However, during summer, the spread of the RCMs—in particular in terms of precipitation—is larger than that of the GCMs. This indicates that the European summer climate is strongly controlled by parameterized physics and/or high-resolution processes. The temperature response is larger than the systematic error. The situation is different for precipitation. The model bias is twice as large as the climate response. The confidence in PRUDENCE results comes from the fact that the models have a similar response to the IPCC-SRES A2 forcing, whereas their systematic errors are more spread. In addition, GCM precipitation response is slightly but significantly different from that of the RCMs.  相似文献   

温室效应对青藏高原及青藏铁路沿线气候影响的数值模拟   总被引：25，自引：12，他引：13  

高学杰  李栋梁  赵宗慈  Filippo Giorgi 《高原气象》2003,22(5):458-463

在一个全球模式中嵌套了RegCM2区域气候模式,进行了CO2加倍对中国区域气候影响的数值试验,对青藏高原及青藏铁路沿线地区进行了重点分析。结果表明,在CO2加倍的情况下,这里的气温将明显升高,升高值一般在2．6～2．8℃以上,高于全国平均值。同时降水在青藏高原大部分地区也将明显增加;其中青藏铁路沿线的增加率一般在25％以上,远高于全国平均值水平。温室效应同时会使得青藏铁路沿线的日平均最高气温升高。  相似文献   

An intercomparison of regional climate simulations for Europe: assessing uncertainties in model projections   总被引：2，自引：0，他引：2  

M. Déqué  D. P. Rowell  D. Lüthi  F. Giorgi  J. H. Christensen  B. Rockel  D. Jacob  E. Kjellström  M. de Castro  B. van den Hurk 《Climatic change》2007,81(1):53-70

Ten regional climate models (RCM) have been integrated with the standard forcings of the PRUDENCE experiment: IPCC-SRES A2 radiative forcing and Hadley Centre boundary conditions. The response over Europe, calculated as the difference between the 2071–2100 and the 1961–1990 means can be viewed as an expected value about which various uncertainties exist. Uncertainties are measured here by variance in eight sub-European boxes. Four sources of uncertainty can be evaluated with the material provided by the PRUDENCE project. Sampling uncertainty is due to the fact that the model climate is estimated as an average over a finite number of years (30). Model uncertainty is due to the fact that the models use different techniques to discretize the equations and to represent sub-grid effects. Radiative uncertainty is due to the fact that IPCC-SRES A2 is merely one hypothesis. Some RCMs have been run with another scenario of greenhouse gas concentration (IPCC-SRES B2). Boundary uncertainty is due to the fact that the regional models have been run under the constraint of the same global model. Some RCMs have been run with other boundary forcings. The contribution of the different sources varies according to the field, the region and the season, but the role of boundary forcing is generally greater than the role of the RCM, in particular for temperature. Maps of minimum expected 2m temperature and precipitation responses for the IPCC-A2 scenario show that, despite the above mentioned uncertainties, the signal from the PRUDENCE ensemble is significant.  相似文献   

中国当代土地利用对区域气候影响的数值模拟   总被引：20，自引：0，他引：20  

高学杰  张冬峰  陈仲新  Jeremy S.Pal  Filippo Giorgi 《中国科学D辑》2007,37(3):397-404

使用RegCM3区域气候模式，嵌套欧洲数值预报中心(ECMWF)ERA40再分析资料，分别进行了中国区域在实际植被和理想植被分布情况下各15年时间长度（1987-2001）的积分试验，以研究我国土地利用状况对气候的影响。通过两个试验结果的对比，研究了我国土地利用状况对气候的影响。分析主要集中于气温、降水等的变化上，并对结果进行了统计显著性检验。结果表明，当代土地利用/植被覆盖变化加强了中国地区冬、夏季的季风环流，同时改变了地表能量平衡状况，从而对各气候要素产生重要影响。冬季，植被改变引起长江以南降水减少、气温降低，长江以北降水增加。夏季，植被改变显著影响了南方地区的气候，使得这里降水增多，黄淮、江淮气温降低，华南气温上升；同时引起中国北方降水减少，气温在西北部分植被退化地区升高。植被变化对日最低、最高气温的影响更大。总体来说，土地利用引起了年平均降水在南方增加、北方减少，年平均气温在南方显著降低。  相似文献   

Simulating future Caspian sea level changes using regional climate model outputs     

N. Elguindi  F. Giorgi 《Climate Dynamics》2007,28(4):365-379

We report on simulations of present-day climate (1961–1990) and future climate conditions (2071–2100, Special Report on Emissions Scenario A2) over the Caspian sea basin with a regional climate model (RCM) nested in time-slice general circulation model (GCM) simulations. We also calculate changes (A2 scenario minus present-day) in Caspian sea level (CSL) in response to changes in the simulated hydrologic budget of the basin. For the present-day run, both the GCM and RCM show a good performance in reproducing the water budget of the basin and the magnitude of multi-decadal changes in CSL. Compared to present-day climate, in the A2 scenario experiment we find an increase in cold season precipitation and an increase in temperature and evaporation, both over land and over the Caspian sea. We also find a large decrease of CSL in the A2 scenario run compared to the present-day run. This is due to increased evaporation loss from the basin (particularly over the sea) exceeding increased cold season precipitation over the basin. Our results suggest that the CSL might undergo large changes under future climate change, leading to potentially devastating consequences for the economy and environment of the region.  相似文献   

Assessment of RegCM4 simulated inter-annual variability and daily-scale statistics of temperature and precipitation over Mexico     

Ramón Fuentes-Franco  Erika Coppola  Filippo Giorgi  Federico Graef  Edgar G. Pavia 《Climate Dynamics》2014,42(3-4):629-647

The skill of a regional climate model (RegCM4) in capturing the mean patterns, interannual variability and extreme statistics of daily-scale temperature and precipitation events over Mexico is assessed through a comparison of observations and a 27-year long simulation driven by reanalyses of observations covering the Central America CORDEX domain. The analysis also includes the simulation of tropical cyclones. It is found that RegCM4 reproduces adequately the mean spatial patterns of seasonal precipitation and temperature, along with the associated interannual variability characteristics. The main model bias is an overestimation of precipitation in mountainous regions. The 5 and 95 percentiles of daily temperature, as well as the maximum dry spell length are realistically simulated. The simulated distribution of precipitation events as well as the 95 percentile of precipitation shows a wet bias in topographically complex regions. Based on a simple detection method, the model produces realistic tropical cyclone distributions even at its relatively coarse resolution (dx = 50 km), although the number of cyclone days is underestimated over the Pacific and somewhat overestimated over the Atlantic and Caribbean basins. Overall, it is assessed that the performance of RegCM4 over Mexico is of sufficient quality to study not only mean precipitation and temperature patterns, but also higher order climate statistics.  相似文献   

Seasonal and intraseasonal changes of African monsoon climates in 21st century CORDEX projections   总被引：1，自引：0，他引：1  

L. Mariotti  I. Diallo  E. Coppola  F. Giorgi 《Climatic change》2014,125(1):53-65

We analyze a mini ensemble of regional climate projections over the CORDEX Africa domain carried out with RegCM4 model as part of the Phase I CREMA experiment (Giorgi 2013). RegCM4 is driven by the HadGEM2-ES and MPI-ESM global models for the RCP8.5 and RCP4.5 greenhouse gas and aerosol concentration scenarios. The focus of the analysis is on seasonal and intraseasonal monsoon characteristics. We find two prominent change signals. Over West Africa and the Sahel MPI produces a forward shift in the monsoon season in line with previous findings, and this shift is also simulated by the RegCM4. Furthermore, the regional model produces a widespread decrease of monsoon precipitation (when driven by both MPI and HadGEM) associated with decreased easterly wave activity in the 6–9 days regime and with soil moisture-precipitation interactions. South of the equator we find an extension of the dry season with delayed onset and anticipated recession of the monsoon and a narrowing and strengthening of the ITCZ precipitation band. This signal is consistent in all global and regional model projections, although with different spatial detail. We plan to enlarge this mini-ensemble as a further contribution to the CORDEX project to better assess the robustness of the signals found in this paper.  相似文献