Stage‐discharge uncertainty derived with a non‐stationary rating curve in the Choluteca River,Honduras     

I. Westerberg  J.‐L. Guerrero  J. Seibert  K. J. Beven  S. Halldin 《水文研究》2011,25(4):603-613

Uncertainty in discharge data must be critically assessed before data can be used in, e.g. water resources estimation or hydrological modelling. In the alluvial Choluteca River in Honduras, the river‐bed characteristics change over time as fill, scour and other processes occur in the channel, leading to a non‐stationary stage‐discharge relationship and difficulties in deriving consistent rating curves. Few studies have investigated the uncertainties related to non‐stationarity in the stage‐discharge relationship. We calculated discharge and the associated uncertainty with a weighted fuzzy regression of rating curves applied within a moving time window, based on estimated uncertainties in the observed rating data. An 18‐year‐long dataset with unusually frequent ratings (1268 in total) was the basis of this study. A large temporal variability in the stage‐discharge relationship was found especially for low flows. The time‐variable rating curve resulted in discharge estimate differences of ? 60 to + 90% for low flows and ± 20% for medium to high flows when compared to a constant rating curve. The final estimated uncertainty in discharge was substantial and the uncertainty limits varied between ? 43 to + 73% of the best discharge estimate. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Deep seismic reflectivity patterns in specific tectonic units of Western and Central Europe   总被引：2，自引：0，他引：2  

Petra Sadowiak  Thomas Wever  Rolf Meissner 《Geophysical Journal International》1991,105(1):45-54

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Freshwater geographies: Experimenting with knowing and doing geography differently   总被引：1，自引：0，他引：1  

Brendon Blue  Claire Gregory  Kiely McFarlane  Marc Tadaki  Petra van Limburg‐Meijer  Nick Lewis 《New Zealand geographer》2012,68(1):62-66

The fair and effective governance of freshwater is an increasingly prominent issue in New Zealand. Emerging from a complex of cultural, economic and biophysical narratives, freshwater geographies are multiple, varied and increasingly acknowledged as worthy of interdisciplinary scrutiny. In this commentary, we reflect on a series of generative spaces that we – as group of postgraduate geographers (plus supporting staff) – created to engage with the multiplicity of freshwater meanings both within and beyond the academy. Through this evolving epistemic‐political project, we significantly reframed our own understandings about what freshwater ‘is’ and how it ought to be governed. By pursuing a deeper understanding of how the world gets made, we expand our ability to know and make it differently.  相似文献   

Changes in ice-season characteristics of a European Arctic lake from 1964 to 2008     

Ruibo Lei  Matti Lepp?ranta  Bin Cheng  Petra Heil  Zhijun Li 《Climatic change》2012,115(3-4):725-739

The long-term ice record (from 1964 to 2008) of an Arctic lake in northern Europe (Lake Kilpisj?rvi) reveals the response of lake ice to climate change at local and regional scales. Average freeze-up and ice breakup occurred on 9 November and 19 June, respectively. The freeze-up has been significantly delayed at a rate of 2.3 d per decade from 1964 onward (P?<?0.05). No significant change has taken place in ice breakup. Annual average ice thickness has become smaller since the mid-1980s (P?<?0.05). Air temperature during the early ice season significantly affected the ice thickness. The freeze-up date exhibits the highest correlation with the 2-month average daily minimum air temperature centered at the end of October, while the ice breakup date exhibits the highest correlation with the 2-month average daily maximal air temperature centered in mid May. A 1°C increase in the surface air temperature corresponds to a freeze-up later by 3.4?days and an ice breakup earlier by 3.6?days. Snow cover is a critical factor in lake-ice climatology. For cumulative November to March precipitation of less than 0.13?m, the insulating effect of the snow dominated, while higher rates of precipitation favored thicker ice due to the formation of snow ice. Variations in ice records of Lake Kilpisj?rvi can serve as an indicator of climate variations across the northern Europe. The North Atlantic Oscillation (NAO) does not significantly affect the ice season there, although both the local air temperatures and winter precipitation contain a strong NAO signal.  相似文献   

Floods in the Sahel: an analysis of anomalies, memory, and anticipatory learning     

Petra Tschakert  Regina Sagoe  Gifty Ofori-Darko  Samuel Nii Codjoe 《Climatic change》2010,103(3-4):471-502

This study explores the implications of recent extreme rainfall and flood events in the Sahel and the wider West African region for climate change adaptation. Are these events merely a temporal nuisance as suggested by the lingering desertification discourse or will more climatic extremes characterize the region over the next century? After reviewing incidences of severe rainfall and projected future climate variability, the paper examines local flood knowledge and decision-making, drawing upon a case study in Ghana. The data demonstrate that a variety of response strategies to flooding exist; yet, knowledge of and access to climate forecasts and other learning tools are essentially absent. So far, floods have not triggered mass displacement although cumulative environmental deterioration is likely to cause environmental refugees. The paper recommends to lay to rest the desertification narrative, consider the possibility of both floods and droughts, and mobilize local memory for anticipatory learning and practical adaptation.  相似文献   

Uncertainties in climate change prediction: El Niño-Southern Oscillation and monsoons     

Heiko Paeth  Anja Scholten  Petra Friederichs  Andreas Hense 《Global and Planetary Change》2008,60(3-4):265-288

The sensitivity of climate phenomena in the low latitudes to enhanced greenhouse conditions is a scientific issue of high relevance to billions of people in the poorest countries of the globe. So far, most studies dealt with individual model results. In the present analysis, we refer to 79 coupled ocean–atmosphere simulations from 12 different climate models under 6 different IPCC scenarios. The basic question is as to what extent various state-of-the-art climate models agree in predicting changes in the main features of El Niño-Southern Oscillation (ENSO) and the monsoon climates in South Asia and West Africa. The individual model runs are compared with observational data in order to judge whether the spatio-temporal characteristics of ENSO are well reproduced. The model experiments can be grouped into multi-model ensembles. Thus, climate change signals in the classical index time series, in the principal components and in the time series of interannual variability can be evaluated against the background of internal variability and model uncertainty.There are large differences between the individual model predictions until the end of the 21st century, especially in terms of monsoon rainfall and the Southern Oscillation index (SOI). The majority of the models tends to project La Niña-like anomalies in the SOI and an intensification of the summer monsoon precipitation in India and West Africa. However, the response barely exceeds the level of natural variability and the systematic intermodel variations are larger than the impact of different IPCC scenarios. Nonetheless, there is one prominent climate change signal, which stands out from model variations and internal noise: All forced model experiments agree in predicting a substantial warming in the eastern tropical Pacific. This oceanic heating does not necessarily lead to a modification of ENSO towards more frequent El Niño and/or La Niña events. It simply represents a change in the background state of ENSO. Indeed, we did not find convincing multi-model evidence for a modification of the wavelet spectra in terms of ENSO or the monsoons. Some models suggest an intensification of the annual cycle but this signal is fairly model-dependent. Thus, large model uncertainty still exists with respect to the future behaviour of climate in the low latitudes. This has to be taken into account when addressing climate change signals in individual model experiments and ensembles.  相似文献   

Quality and timing of crowd-based water level class observations     

Simon Etter  Barbara Strobl  Ilja van Meerveld  Jan Seibert 《水文研究》2020,34(22):4365-4378

Crowd-based hydrological observations can supplement existing monitoring networks and allow data collection in regions where otherwise no data would be available. In the citizen science project CrowdWater, repeated water level observations using a virtual staff gauge approach result in time series of water level classes (WL-classes). To investigate the quality of these observations, we compared the WL-class data with “real” (i.e., measured) water levels from the same stream at a nearby gauging station. We did this for nine locations where citizen scientists reported multiple observations using a smartphone app and at 12 locations where signposts were set up to ask citizens to record observations on a paper form that could be left in a letterbox. The results indicate that the quality of the data collected with the app was better than for the forms. A possible explanation is that for each app location, a single person submitted the vast majority of the observations, whereas at the locations of the forms almost every observation was made by a different person. On average, there were more contributions between May and September than during the other months. Observations were submitted for a range of flow conditions, with a higher fraction of high flow observations for the locations were data were collected with the app. Overall, the results are encouraging for citizen science approaches in hydrology and demonstrate that the smartphone application and the virtual staff gauge are a promising approach for crowd-based water level class observations.  相似文献   

Geophysical evidence of the Eastern Marginal Fault of the Cheb Basin (Czech Republic)     

Vratislav Blecha  Tomáš Fischer  Petr Tábořík  Jan Vilhem  Radek Klanica  Jan Valenta  Petra Štěpančíková 《Studia Geophysica et Geodaetica》2018,62(4):660-680

The western part of the Bohemian Massif hosts an intersection of two regional fault zones, the SW-NE trending Oh?e/Eger Graben and the NNW-SSE trending Mariánské Lázně Fault, which has been reactivated several times in the geological history and controlled the formation of the Tertiary Cheb Basin. The broader area of the Cheb Basin is also related to permanent seismic activity of M_L 3+ earthquake swarms. The Eastern Marginal Fault of the Cheb Basin (northern segment of the Mariánské Lázně Fault) separates the basin sediments and underlying granites in the SW from the Kru?né Hory/Erzgebirge Mts. crystalline unit in the NE. We describe a detailed geophysical survey targeted to locating the Eastern Marginal Fault and determining its geometry in the depth. The survey was conducted at the Kopanina site near the Nový Kostel focal zone, which shows the strongest seismic activity of the whole Western Bohemia earthquake swarm region. Complex geophysical survey included gravimetry, electrical resistivity tomography, audiomagnetotellurics and seismic refraction. We found that the rocks within the Eastern Marginal Fault show low resistivity, low seismic velocity and density, which indicates their deep fracturing, weathering and higher water content. The dip of the fault in shallow depths is about 60° towards SW. At greater depths, the slope turns to subvertical with dip angle of about 80°. Results of geoelectrical methods show blocky fabric of the Cheb Basin and deep weathering of the granite bedrock, which is consistent with geologic models based on borehole surveys.  相似文献   

Magic components—why quantifying rain,snowmelt, and icemelt in river discharge is not easy          下载免费PDF全文

Markus Weiler  Jan Seibert  Kerstin Stahl 《水文研究》2018,32(1):160-166

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Seismic behaviour of masonry buildings built of low compressive strength units     

Petra Triller  Miha Tomaževič  Matija Gams 《Bulletin of Earthquake Engineering》2018,16(12):6191-6219

Seismic behaviour of masonry buildings, built of low compressive strength units, is discussed. Although such materials have already been tested and approved for use from mechanical and thermal insulation point of view, the knowledge regarding their structural behaviour is still lacking. In order to investigate the resistance and deformation capacity of this particular type of masonry construction in seismic conditions, a series of eight walls and model of a two-storey full scale confined masonry building have been tested by subjecting the specimens to cyclic shear loads. All tests were conducted under a combination of constant vertical load and quasi static, cyclically imposed horizontal load. The behaviour of tested specimens was of typical shear type. Compared with the behaviour of plain masonry walls, the presence of tie-columns resulted into higher resistance and displacement capacity, as well as smaller lateral resistance degradation. The response of the model was determined by storey mechanism with predominant shear behaviour of the walls and failure mechanism of the same type as in the case of individual confined masonry walls. Adequate seismic behaviour of this particular masonry structural type can be expected under the condition that the buildings are built as confined masonry system with limited number of stories.  相似文献