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Binquan?LiEmail authorView author&#;s OrcID profile Zhongmin?Liang Yingqing?He Lin?Hu Weimin?Zhao Kumud?Acharya 《Stochastic Environmental Research and Risk Assessment (SERRA)》2017,31(5):1045-1059
Parameter uncertainty in hydrologic modeling is crucial to the flood simulation and forecasting. The Bayesian approach allows one to estimate parameters according to prior expert knowledge as well as observational data about model parameter values. This study assesses the performance of two popular uncertainty analysis (UA) techniques, i.e., generalized likelihood uncertainty estimation (GLUE) and Bayesian method implemented with the Markov chain Monte Carlo sampling algorithm, in evaluating model parameter uncertainty in flood simulations. These two methods were applied to the semi-distributed Topographic hydrologic model (TOPMODEL) that includes five parameters. A case study was carried out for a small humid catchment in the southeastern China. The performance assessment of the GLUE and Bayesian methods were conducted with advanced tools suited for probabilistic simulations of continuous variables such as streamflow. Graphical tools and scalar metrics were used to test several attributes of the simulation quality of selected flood events: deterministic accuracy and the accuracy of 95 % prediction probability uncertainty band (95PPU). Sensitivity analysis was conducted to identify sensitive parameters that largely affect the model output results. Subsequently, the GLUE and Bayesian methods were used to analyze the uncertainty of sensitive parameters and further to produce their posterior distributions. Based on their posterior parameter samples, TOPMODEL’s simulations and the corresponding UA results were conducted. Results show that the form of exponential decline in conductivity and the overland flow routing velocity were sensitive parameters in TOPMODEL in our case. Small changes in these two parameters would lead to large differences in flood simulation results. Results also suggest that, for both UA techniques, most of streamflow observations were bracketed by 95PPU with the containing ratio value larger than 80 %. In comparison, GLUE gave narrower prediction uncertainty bands than the Bayesian method. It was found that the mode estimates of parameter posterior distributions are suitable to result in better performance of deterministic outputs than the 50 % percentiles for both the GLUE and Bayesian analyses. In addition, the simulation results calibrated with Rosenbrock optimization algorithm show a better agreement with the observations than the UA’s 50 % percentiles but slightly worse than the hydrographs from the mode estimates. The results clearly emphasize the importance of using model uncertainty diagnostic approaches in flood simulations. 相似文献
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Statistical downscaling of extremes of precipitation and temperature and construction of their future scenarios in an elevated and cold zone 总被引：5，自引：4，他引：1
Xiaoyan?Wang Tao?YangEmail author Quanxi?Shao Kumud?Acharya Weiguang?Wang Zhongbo?Yu 《Stochastic Environmental Research and Risk Assessment (SERRA)》2012,26(3):405-418
Reliable projections of extremes at finer spatial scales are important in assessing the potential impacts of climate change
on societal and natural systems, particularly for elevated and cold regions in the Tibetan Plateau. This paper presents future
projections of extremes of daily precipitation and temperature, under different future scenarios in the headwater catchment
of Yellow River basin over the 21st century, using the statistical downscaling model (SDSM). The results indicate that: (1)
although the mean temperature was simulated perfectly, followed by monthly pan evaporation, the skill scores in simulating
extreme indices of precipitation are inadequate; (2) The inter-annual variabilities for most extreme indices were underestimated,
although the model could reproduce the extreme temperatures well. In fact, the simulation of extreme indices for precipitation
and evaporation were not satisfactory in many cases. (3) In future period from 2011 to 2100, increases in the temperature
and evaporation indices are projected under a range of climate scenarios, although decreasing mean and maximum precipitation
are found in summer during 2020s. The findings of this work will contribute toward a better understanding of future climate
changes for this unique region. 相似文献
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Drought identification and drought severity characterization are crucial to understand water scarcity processes. Evolution of drought and wetness episodes in the upper Nen River (UNR) basin have been analyzed for the period of 1951–2012 using meteorological drought indices and for the period of 1898–2010 using hydrological drought indices. There were three meteorological indices: one based on precipitation [the Standardized Precipitation Index (SPI)] and the other two based on water balance with different formulations of potential evapotranspiration (PET) in the Standardized Precipitation Evapotranspiration Index (SPEI). Moreover, two hydrological indices, the Standardized Runoff Index and Standardized Streamflow Index, were also applied in the UNR basin. Based on the meteorological indices, the results showed that the main dry period of 1965–1980 and wet periods of 1951–1964 and 1981–2002 affected this cold region. It was also found that most areas of the UNR basin experienced near normal condition during the period of 1951–2012. As a whole, the UNR basin mainly had the drought episodes in the decades of 1910, 1920, 1970 and 2000 based on hydrological indices. Also, the severity of droughts decreased from the periods of 1898–1950 to 1951–2010, while the severity of floods increased oppositely during the same periods. A correlation analysis showed that hydrological system needs a time lag of one or more months to respond to meteorological conditions in this cold region. It was also found that although precipitation had a major role in explaining temporal variability of drought, the influence of PET was not negligible. However, the sole temperature driver of PET had an opposite effect in the UNR basin (i.e., misestimating the drought detection) and was inferior to the SPI, which suggests that the PET in the SPEI should be determined by using underlying physical principles. This finding is an important implication for the drought research in future. 相似文献
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选取国内外常用的水动力学模型(EFDC)和典型的浅水湖泊(太湖),采用拉丁超立方取样(LHS),研究湖泊水动力模块中常用的5个重要参数(风拖曳系数、床面粗糙高度、涡粘性系数、紊流扩散系数以及风遮挡系数)对湖体水位和流速的影响。结果表明:针对大型浅水湖泊,湖泊岸线形状和湖底地形、湖泊周围地形、湖泊水面风场对模拟结果产生决定性影响。尤其是在湖湾区和周边地形比较复杂的地区,风场参数对水动力模拟结果不确定性的贡献率最大。在垂向上,表层流速受到参数不确定性的影响最大,底层次之,中层最小。床面粗糙高度对水动力模拟结果不确定性贡献率较风场参数要小,水体涡粘滞系数和扩散系数影响则更小。故在选择大型浅水湖泊水动力模型参数时,要充分考虑湖泊岸线和周围地形,着重率定风场参数以及床面粗糙高度。 相似文献
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Wind-induced hydrodynamic changes impact on sediment resuspension for large,shallow Lake Taihu,China
Abdul Jalil Yiping Li Ke Zhang Xiaomeng Gao Wencai Wang Hafiz Osama Sarwar Khan Baozhu Pan Salar Ali Kumud Acharya 《国际泥沙研究》2019,34(3):205-215
The internal sediment release is a key factor controlling eutrophication processes in large, shallow lakes. Sediment resuspension is associated with the wave and current induced shear stress in large, shallow lakes. The current study investigated the wind field impacts on sediment resuspension from the bottom at Meiliang Bay of large, shallow Lake Taihu. The impacts of the wind field on the wave, current, and wave-current combined shear stresses were calculated. The critical wind speed range was 4–6?m/s after which wave and current shear stress started to increase abruptly, and onshore wind directions were found to be mainly responsible for greater shear stress at the bottom of Lake Taihu. A second order polynomial fitting correlation was found between wave (R2 0.4756) and current (R2 0.4466) shear stresses with wind speed. Wave shear stress accounted for 92.5% of the total shear stress at Meiliang Bay. The critical wave shear stress and critical total shear stress were 0.13?N/m2 for sediment resuspension whereas the current shear stress was 0.019?N/m2 after which suspended sediment concentrations (SSC) increased abruptly. A second order polynomial fitting correlation was found between wave (R2 0.739), current (R2 0.6264), and total shear stress (R2 0.7394) with SSC concentrations at Meiliang Bay of Lake Taihu. The sediment resuspension rate was 120 to 738?g/m2/d during 4–6?m/s onshore winds while offshore winds contributed ≥ 200?g/m2/d. The study results reveal the driving mechanism for understanding the role of the wind field in sediment resuspension while considering wind speed and direction as control parameters to define wave and current shear stresses. 相似文献
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Nishant Mittal Kumud Pandey Udit Narain S. S. Sharma 《Astrophysics and Space Science》2009,323(2):135-145
We have investigated properties such as speed, angular width, location, acceleration and occurrence rate of narrow CMEs (defined
as having angular width ≤20°) observed during 1996–2007 by SOHO/LASCO. The results obtained are compared with those of normal
CMEs (angular width >20°) from the same time interval to find whether there are any real differences between the two populations.
Our study of 3464 narrow CMEs from the online SOHO/LASCO, CME catalogue leads us to conclude that (1) the fraction of narrow
CMEs during solar minimum is 38% and during solar maximum 19%, (2) during solar maximum narrow CMEs are generally faster than
normal CMEs, (3) the maximum speed of narrow CMEs is much smaller than that of the normal CMEs, (4) during solar maximum narrow
CMEs appear at all latitudes similar to normal CMEs, (5) narrow and normal CMEs have unequal deceleration and (6) the occurrence
rate of narrow CMEs remain constant after 1998 until the beginning of 2006 while the normal CMEs occurrence rate seems to
follow solar cycle variation until 2004. Thus narrow CMEs and normal CMEs have some differences, in disagreement with previous
studies. 相似文献
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引调水是改善平原河网地区水环境的重要方法之一,通过构建太湖流域走马塘东南片平原河网区一维水动力水质数学模型,研究不同引调水方案对区域水环境改善效果,确定引调水过程中的异质性因子.从决策目标、水质指标、空间指标3个层面综合考虑,构建环境效益与经济效益结合的多目标函数及评价体系,对引调水方案进行评估优选.结果表明:引调水流量较大时,能够在一定程度上改善区域水环境状况,规划方案下引调水5 d后,高锰酸盐指数、氨氮、总磷的平均改善率分别为30.7%、22.2%、26.4%;引调水时,区域河网中不同空间点位、不同水质指标之间的水质改善过程与效果都存在一定异质性;引调水水量、调度模式及污染源分布都会对调水后的河网区水质产生差异性影响;本研究建立的多目标评价体系较现有方法能够有效涵盖引调水中存在的异质性因子,从多个目标层面优选引调水方案,实现水量水质综合优化调控,为平原河网地区水环境长效管理与科学决策提供理论参考. 相似文献
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