Nitrate contamination of groundwater in the western Po Plain (Italy): the effects of groundwater and surface water interactions     

Manuela Lasagna  Domenico Antonio De Luca  Elisa Franchino 《Environmental Earth Sciences》2016,75(3):240

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Combination of GNSS and SLR observations using satellite co-locations   总被引：6，自引：6，他引：0  

Daniela Thaller  Rolf Dach  Manuela Seitz  Gerhard Beutler  Maria Mareyen  Bernd Richter 《Journal of Geodesy》2011,85(5):257-272

Satellite Laser Ranging (SLR) observations to Global Navigation Satellite System (GNSS) satellites may be used for several purposes. On one hand, the range measurement may be used as an independent validation for satellite orbits derived solely from GNSS microwave observations. On the other hand, both observation types may be analyzed together to generate a combined orbit. The latter procedure implies that one common set of orbit parameters is estimated from GNSS and SLR data. We performed such a combined processing of GNSS and SLR using the data of the year 2008. During this period, two GPS and four GLONASS satellites could be used as satellite co-locations. We focus on the general procedure for this type of combined processing and the impact on the terrestrial reference frame (including scale and geocenter), the GNSS satellite antenna offsets (SAO) and the SLR range biases. We show that the combination using only satellite co-locations as connection between GNSS and SLR is possible and allows the estimation of SLR station coordinates at the level of 1–2 cm. The SLR observations to GNSS satellites provide the scale allowing the estimation of GNSS SAO without relying on the scale of any a priori terrestrial reference frame. We show that the necessity to estimate SLR range biases does not prohibit the estimation of GNSS SAO. A good distribution of SLR observations allows a common estimation of the two parameter types. The estimated corrections for the GNSS SAO are 119 mm and −13 mm on average for the GPS and GLONASS satellites, respectively. The resulting SLR range biases suggest that it might be sufficient to estimate one parameter per station representing a range bias common to all GNSS satellites. The estimated biases are in the range of a few centimeters up to 5 cm. Scale differences of 0.9 ppb are seen between GNSS and SLR.  相似文献   

GEOALGAR项目:地震活动性和断层面解的初步结果     

F.Carrilho　P.Teves-Costa　I.Morais　J.Pagarete　R.Dias 《国际地震动态》2004,(10):27-36

2000年5月发起的GEOALGAR项目旨在致力于阿尔加维地区的地球动力学监测和地震区划. 本文简单介绍一下该项目的目标和有关1999-2000年地震记录分析的初步结果. 经过地震记录和速度模型参数的同步反演, 对两个选定区域的震源位置进行了重新定位. 区域1使用了25个1999-2000年间发生的ML≥2.0的地震, 区域2使用了125个. 结果表明, 主要有两个地区的地震较多 一个是蒙希克地区(在内陆), 另一个是瓜达尔基维尔浅滩(范围从36.4°N, 8°W～36.8°N, 7.2°W). 区域1, 震源校正的幅度相对较小, 震源比原先定位的深度稍微深一些; 而对于区域范围内其他更多的地震, 震源校正的幅度较大, 震源的位置变得更浅.对于近期发生的地震也做了断层面解的估计, 结果表明, 最优解受到走滑运动的控制, 这与NW-SE至NNW-SSE方向的水平挤压控制的应力一致, 有两个地震例外, 它们呈现的是逆冲机制, 最大水平挤压应力方向稍微转向N-S. 这与其他作者先前研究的结果也是一致的.重新定位后的震中位置在空间分布上显得更加有条理, 表明它与一些已知的构造特征可能相关. 然而, 断层面解的结果与新构造特征很难相关起来.  相似文献   

Spring drought prediction based on winter NAO and global SST in Portugal          下载免费PDF全文

João Filipe Santos  Maria Manuela Portela  Inmaculada Pulido‐Calvo 《水文研究》2014,28(3):1009-1024

The aim of this paper is to test the ability of neural network approaches to hindcast the spring standardized precipitation index on a 6‐month time scale (SPI6) in Portugal, based on winter large‐scale climatic indices. For this purpose, the linkage of the spring SPI time series with the winter North Atlantic Oscillation (NAO) and the sea surface temperature (SST) was investigated by means of maps of the correlation coefficient for the period from October 1910 to September 2004. The results indicate that the winter NAO is a good predictor for the SPI6 of the spring (SPI6 finishing in April, May and June, SPI6_April, SPI6_May and SPI6_June, respectively) for the northern, central and southern regions of Portugal. The winter SST1 (area of the Mediterranean Sea) must only be considered for the northern region, and the winter SST3 (area of the North Atlantic between Iberia and North America) only for the southern region. Spatial maps of predictive SPI6 for April, May and June were created and validated. The neural models explained more than 81% of the total variance for the SPI6_April and SPI6_May and more than 64% of the total variance for the SPI6_June. Probability maps were also developed considering the values predicted by the neural methods for the spring months and all drought categories (moderate, severe and extreme). These maps indicating the probability of droughts can provide valuable support for the integrated planning and management of water resources throughout Portugal. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Anomalous far‐field geodetic signature related to the 2009 L'Aquila (central Italy) earthquake     

Simone Atzori  Claudio Chiarabba  Roberto Devoti  Manuela Bonano  Riccardo Lanari 《地学学报》2013,25(5):343-351

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Quantitative methods for estimating flood fatalities: towards the introduction of loss-of-life estimation in the assessment of flood risk   总被引：1，自引：0，他引：1  

Manuela Di Mauro  Karin M. De Bruijn  Matteo Meloni 《Natural Hazards》2012,63(2):1083-1113

Risk, including flood risk, can be defined as ??the combination of the probability of an event and its consequences??. Assessing and managing the risk from flooding should explicitly include the estimation of impacts to people. Extensive research is currently ongoing looking at both quantitative and qualitative approaches for assessing flood impacts on people. Although there is some literature available on such approaches, examples of methodological and routinely applications of these methodologies as part of flood risk assessments are rare. This paper focuses on quantitative approaches for estimating impacts of flooding to people, notably on methods for assessing fatality numbers associated with flooding. Three methods for assessing losses of life are discussed in detail. The methods discussed here constitute the forefront of research in Canada, UK and The Netherlands. These methods provide an assessment of the physical consequences of flooding on people and can be used to introduce the impacts to people as quantitative metric for the assessment of flood risk. In this paper, the three methodologies are discussed and applied in a UK case study reproducing the 1953 East Coast flood event. This study aims to provide a comprehensive comparison on both the reliability and the applicability of the methods. We analyse possible added values on using of these methods in systematic analyses, aiming to provide guidelines for applying these methods for flood fatality risk assessment.  相似文献   

Mars mesospheric zonal wind around northern spring equinox from infrared heterodyne observations of CO2     

Guido Sonnabend  Manuela Sornig  Peter Kroetz  Dusan Stupar 《Icarus》2012,217(1):315-321

We present direct observations of Mars zonal wind velocities around northern spring equinox (L_S = 336°, L_S = 355°, L_S = 42°) during martian year 27 and 29. Data was acquired by means of infrared heterodyne spectroscopy of CO₂ features at 959.3917 cm^?1 (10.4232 μm) and 957.8005 cm^?1 (10.4405 μm) using the Cologne Tuneable Heterodyne Infrared Spectrometer (THIS) at the McMath–Pierce telescope of the National Solar Observatory on Kitt Peak in Arizona and the NASA Infrared Telescope Facility on Mauna Kea, Hawaii between 2005 and 2008. Winds were measured on the dayside of Mars with an unprecedented spatial resolution allowing sampling of up to nine independent latitudes over the martian disk. Retrieved wind velocities depend strongly on latitude and season with values ranging from 180 m/s prograde to ?94 m/s retrograde. A comparison of the observational results to predicted values from the Mars Climate Database yield a reasonable agreement between modeling and observation.  相似文献   

Inverse modeling of coastal aquifers using tidal response and hydraulic tests   总被引：3，自引：0，他引：3  

Alcolea A  Castro E  Barbieri M  Carrera J  Bea S 《Ground water》2007,45(6):711-722

Remediation of contaminated aquifers demands a reliable characterization of hydraulic connectivity patterns. Hydraulic diffusivity is possibly the best indicator of connectivity. It can be derived using the tidal response method (TRM), which is based on fitting observations to a closed-form solution. Unfortunately, the conventional TRM assumes homogeneity. The objective of this study was to overcome this limitation and use tidal response to identify preferential flowpaths. Additionally, the procedure requires joint inversion with hydraulic test data. These provide further information on connectivity and are needed to resolve diffusivity into transmissivity and storage coefficient. Spatial variability is characterized using the regularized pilot points method. Actual application may be complicated by the need to filter tidal effects from the response to pumping and by the need to deal with different types of data, which we have addressed using maximum likelihood methods. Application to a contaminated artificial coastal fill leads to flowpaths that are consistent with the materials used during construction and to solute transport predictions that compare well with observations. We conclude that tidal response can be used to identify connectivity patterns. As such, it should be useful when designing measures to control sea water intrusion.  相似文献   

The cenozoic aquifer system of the Lower Tagus Basin: a description of the hydrogeological situation in the Almada region (Portugal)   总被引：1，自引：0，他引：1  

Maria Manuela Malhado Simões Ribeiro 《Hydrogeology Journal》2009,17(4):999-1009

A conceptual hydrogeological model of the Mio-Pleistocene deposits in the Almada region, located in the Cenozoic aquifer system of the Lower Tagus Basin (Portugal), has been developed. Though numerous studies have been conducted on its geological features, there have not been enough hydrogeological investigations to define the origin, flow path and the groundwater quality and to understand the coexistence of overlapped interacting aquifers. Therefore, a study is presented here on the occurrences and features of groundwater resources in the Almada region based on an inventory in the field (wells, springs and boreholes), physical and chemical analyses, geologic setting, and tectonic and geomorphologic observations. This aquifer system has long been a source of concern because of the high level of extraction over the last few decades, as well as the progressive degradation of the water quality. Available groundwater resources have been affected by intensive agricultural and industrial activity, as a consequence of incorrect or non-existent hydrogeological knowledge.  相似文献   

Hydraulic failure of diaphragm walls: a possible methodology for safety improvement     

Vincenzo Pane  Diego Bellavita  Manuela Cecconi  Alessia Vecchietti 《Geotechnical and Geological Engineering》2017,35(2):765-780

The paper presents a methodology aimed at reducing—or even avoiding—the risk of heave and uplift failures of reinforced concrete diaphragm walls. The method is based on the simple concept of increasing the drainage capacity of the embedded portion of the retaining walls. The behaviour of a strutted excavation in a cohesionless soil below groundwater is examined by means of two distinct series of numerical analyses, respectively focused on the hydraulic and mechanical behaviour of the retaining system. It is shown that, for some frequent cases, such methodology is capable to improve the safety of the retaining system with respect to both hydraulic and geotechnical limit states.  相似文献