A multiscaling‐based intensity–duration–frequency model for extreme precipitation          下载免费PDF全文

Hans Van de Vyver 《水文研究》2018,32(11):1635-1647

Rainfall intensity–duration–frequency (IDF) curves are a standard tool in urban water resources engineering and management. They express how return levels of extreme rainfall intensity vary with duration. The simple scaling property of extreme rainfall intensity, with respect to duration, determines the form of IDF relationships. It is supposed that the annual maximum intensity follows the generalized extreme value (GEV) distribution. As well known, for simple scaling processes, the location parameter and scale parameter of the GEV distribution obey a power law with the same exponent. Although, the simple scaling hypothesis is commonly used as a suitable working assumption, the multiscaling approach provides a more general framework. We present a new IDF relationship that has been formulated on the basis of the multiscaling property. It turns out that the GEV parameters (location and scale) have a different scaling exponent. Next, we apply a Bayesian framework to estimate the multiscaling GEV model and to choose the most appropriate model. It is shown that the model performance increases when using the multiscaling approach. The new model for IDF curves reproduces the data very well and has a reasonable degree of complexity without overfitting on the data.  相似文献   

代表性人口空间分布数据集的精度评价——以2010年广东省为例   总被引：1，自引：0，他引：1  

林丹淳  谭敏  刘凯  柳林  朱远辉 《热带地理》2020,40(2):346-356

以人口密度差异显著的广东省为研究区,比较Worldpop、GPW v4和2种中国公里网格人口分布数据集的空间分布一致性,并以第六次全国人口普查数据为真值,按人口密度分为高、中、低3组,从误差的数值分布和空间分布两方面定量评价4种数据集的精度,最后讨论估算误差的可能来源及数据适用性。结果表明,4种网格人口数据集中Worldpop整体精度最高,且在人口密集区的精度也是最高;GPW v4在低人口密度和中人口密度区域精度略高于Worldpop,但对镇街内人口分布细节刻画不够详细;2种中国公里网格人口分布数据集精度较前两者低,主要受空间化方法和模型变量的选择所限制。Worldpop适合用于人口密度中等及人口密度高区域的精细化研究,GPW v4适合用于长时序、最小研究单元大于镇街的研究,第一种中国公里网格人口分布数据集适合用于需要考虑镇街内人口分布和空间异质性的研究,第二种中国公里网格人口分布数据集适用于需要考虑人口分布细节和空间格局变化的长时序研究。  相似文献   

Changes in agricultural virtual water in Central Asia, 1992–2016     

Yan  Ziyan  Tan  Minghong 《地理学报(英文版)》2020,30(11):1909-1920

Journal of Geographical Sciences - In recent years, flows of many rivers and lakes have become reduced in arid and semi-arid regions around the world. The most typical examples of this phenomenon...  相似文献   

Waveform Characteristics of Earthquakes Induced by Hydraulic Fracturing and Mining Activities: Comparison with Those of Natural Earthquakes     

Li  Nan  Li  Baolin  Chen  Dong  Wang  Enyuan  Tan  Yuyang  Qian  Jiawei  Jia  Haishan 《Natural Resources Research》2020,29(6):3653-3674

Natural Resources Research - Some industrial activities, such as underground mining, hydraulic fracturing (HF), can cause microearthquakes and even damaging earthquakes. In recent years, with the...  相似文献   

Leak-off mechanism and pressure prediction for shallow sediments in deepwater drilling     

Qiang Tan  Jingen Deng  Jin Sun  Wei Liu  Baohua Yu 《中国海洋大学学报(英文版)》2018,17(1):65-71

Deepwater sediments are prone to loss circulation in drilling due to a low overburden gradient. How to predict the magnitude of leak-off pressure more accurately is an important issue in the protection of drilling safety and the reduction of drilling cost in deep water. Starting from the mechanical properties of a shallow formation and based on the basic theory of rock-soil mechanics, the stress distribution around a borehole was analyzed. It was found that the rock or soil on a borehole is in the plastic yield state before the effective tensile stress is generated, and the effective tangential and vertical stresses increase as the drilling fluid density increases; thus, tensile failure will not occur on the borehole wall. Based on the results of stress calculation, two mechanisms and leak-off pressure prediction models for shallow sediments in deepwater drilling were put forward, and the calculated values of these models were compared with the measured value of shallow leak-off pressure in actual drilling. The results show that the MHPS (minimum horizontal principle stress) model and the FIF (fracturing in formation) model can predict the lower and upper limits of leak-off pressure. The PLC (permeable lost circulation) model can comprehensively analyze the factors influencing permeable leakage and provide a theoretical basis for leak-off prevention and plugging in deepwater drilling.  相似文献   

发展GNSS基础设施，满足新的科学需求——美国国家科学基金会（NSF）地球科学十年战略规划解读     

王坦  李瑜 《地震地磁观测与研究》2020,41(4):266-269

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Full moment tensor inversion constrained by double-couple focal mechanism for induced seismicity*          下载免费PDF全文

Yuyang Tan  Haijiang Zhang  Junlun Li  Chen Yin  Furong Wu 《地震科学（英文版）》2020,33(4):177-193

In this study, we propose a new method to determine full moment tensor solution for induced seismicity. This method generalizes the full waveform matching algorithm we have developed to determine the double-couple (DC) focal mechanism based on the neighbourhood algorithm. One major difference between the new method and the former one is that we adopt a new misfit function to constrain the candidate moment tensor solutions with respect to a reference DC solution in addition to other misfit terms characterizing the waveform matching. Through synthetic tests using a real passive seismic survey geometry, the results show the new constraint can help better recover the DC components of inverted moment tensors. We further investigate how errors in the velocity model and source location affect the moment tensor solution. The synthetic test results indicate that the constrained inversion is robust in recovering both the DC and non-DC components. We also test the proposed method on several real induced events in an oil/gas field in Oman using the same observation system as synthetic tests. While it is found that the full moment tensor solutions without using the DC constraints have much larger non-DC components than solutions with the DC constraints, both solutions are able to fit the observed waveforms at similar levels. The synthetic and real test results suggest the proposed DC constrained inversion method can reliably retrieve full moment tensor solutions for the induced seismicity.  相似文献   

卡里马塔海峡水体交换的季节变化   总被引：2，自引：0，他引：2  

王研  徐腾飞  李淑江  Susanto R. Dwi  Agustiadi Teguh  Trenggono Mukti  谭伟  魏泽勋 《海洋学报(英文版)》2019,38(4):47-57

Four trawl-resistant bottom mounts, with acoustic Doppler current profilers(ADCPs) embedded, were deployed in the Karimata Strait from November 2008 to June 2015 as part of the South China Sea-Indonesian Seas Transport/Exchange and Impact on Seasonal Fish Migration(SITE) Program, to estimate the volume and property transport between the South China Sea and Indonesian seas via the strait. The observed current data reveal that the volume transport through the Karimata Strait exhibits significant seasonal variation. The winteraveraged(from December to February) transport is –1.99 Sv(1 Sv=1×10~6 m~3/s), while in the boreal summer(from June to August), the average transport is 0.69 Sv. Moreover, the average transport from January 2009 to December2014 is –0.74 Sv(the positive/negative value indicates northward/southward transport). May and September are the transition period. In May, the currents in the Karimata Strait turn northward, consistent with the local monsoon. In September, the southeasterly trade wind is still present over the strait, driving surface water northward, whereas the bottom flow reverses direction, possibly because of the pressure gradient across the strait from north to south.  相似文献   

Monitoring soil surface roughness under growing winter wheat with low-altitude UAV sensing: Potential and limitations     

Nils Onnen  Anette Eltner  Goswin Heckrath  Kristof Van Oost 《地球表面变化过程与地形》2020,45(14):3747-3759

Soil surface roughness (SSR) is an important factor in controlling sediment and runoff generation, influencing directly a wide spectrum of erosion parameters. SSR is highly variable in time and space under natural conditions, and characterizing SSR to improve the parameterization of hydrological and erosion models has proved challenging. Our study uses recent technological and algorithmic developments in capturing and processing close aerial sensing data to evaluate how high-resolution imagery can assist the temporally and spatially explicit monitoring of SSR. We evaluated the evolution of SSR under natural rainfall and growing vegetation conditions on two arable fields in Denmark. Unmanned aerial vehicle (UAV) photogrammetry was used to monitor small field plots over 7 months after seeding of winter wheat following conventional and reduced tillage treatments. Field campaigns were conducted at least once a month from October until April, resulting in nine time steps of data acquisition. Structure from motion photogrammetry was used to derive high-resolution point clouds with an average ground sampling distance of 2.7 mm and a mean ground control point accuracy of 1.8 mm. A comprehensive workflow was developed to process the point clouds, including the detection of vegetation and the removal of vegetation-induced point cloud noise. Rasterized and filtered point clouds were then used to determine SSR geostatistically as the standard deviation of height, applying different kernel sizes and using semivariograms. The results showed an influence of kernel size on roughness, with a value range of 0.2–1 cm of average height deviation during the monitoring period. Semivariograms showed a measurable decrease in sill variance and an increase in range over time. This research demonstrated multiple challenges to measuring SSR with UAV under natural conditions with increasing vegetation cover. The proposed workflow represents a step forward in tackling those challenges and provides a knowledge base for future research. © 2020 John Wiley & Sons, Ltd.  相似文献   

An Application of HFE-D for Evaluating Sea Water Intrusion in Coastal Aquifers of Southern Vietnam     

Thi Thuy Van Le  Rungruang Lertsirivorakul  Tran Vuong Bui  Marcia K. Schulmeister 《Ground water》2020,58(6):1012-1022

The coastal aquifers and inland waters of the Long Xuyen Quadrangle and Ca Mau Peninsula of southern Vietnam have been significantly impacted by sea water intrusion (SI) as a result of recent anthropogenic activities. This study identified the evolution and spatial distribution of hydrochemical conditions in coastal aquifers at this region using Hydrochemical Facies Evolution Diagram (HFE-D) and Geographical Information System mapping. Hydraulic heads and water chemistry were measured at 31 observation wells in four layered aquifers during dry and rainy seasons in early (2005), and more recent (2016), stages of agricultural development. Hydrochemical facies associated with intrusion or freshening stages were mapped in each aquifer after assigning mixing index values to each facies. The position of groundwater freshening and SI phases differed in Holocene, Upper Pleistocene, Middle Pleistocene, and Lower Pleistocene aquifers. The geographic position of freshening and intrusion fronts differ in dry and rainy seasons, and shifted after 11 years of groundwater abstraction in all four aquifers. The spatial and temporal differences in hydrochemical facies distributions according to HFE-D reflect the relative impact of SI in the four aquifers. The study results provide a better understanding of the evolution of groundwater quality associated with SI in a peninsular coastal aquifer system, and highlight the need for improving groundwater quality and management in similar coastal regions.  相似文献