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Trend in Observed and Projected Maximum and Minimum Temperature over N-W Himalayan Basin

Journal of Mountain Science 2015年第2期12卷 417-433页

作者： Dharmaveer SINGH Sanjay K JAIN Rajan Dev GUPTA GIS Cell Motilal Nehru National Institute of Technology Allahabad Water Resources Systems Division National Institute of Hydrology department of Civil Engineering Motilal Nehru National Institute of Technology Allahabad

Recently, study in past trends of climate variables gained significant consideration because of its contribution in adaptions and mitigation strategies for potential future changes in climate, primarily in the area of water resource management. Future interannual and inter-seasonal variations in maximum and minimum temperature may bring significant changes in hydrological systems and affect regional water resources. The present study has been performed to observe past(1970-2010) as well as future(2011-2100)spatial and temporal variability in temperature(maximum and minimum) over selected stations of Sutlej basin located in North-Western Himalayan region in India. The generation of future time series of temperature data at different stations is done using statistical downscaling technique. The nonparametric test methods, modified Mann-Kendall test and Cumulative Sum chart are used for detecting monotonic trend and sequential shift in time series of maximum and minimum temperature. Sen's slope estimator test is used to detect the magnitude of change over a period of time on annual and seasonal basis. The cooling experienced in annual TMax and TMin at Kasol in past(1970-2010) would be replaced by warming in future as increasing trends are detected in TMax during 2020 s and 2050 s and in TMin during 2020 s, 2050 s and 2080 s under A1 B and A2 scenarios. Similar results of warming are also predicted at Sunnifor annual TMin in future under both scenarios which witnessed cooling during 1970-2010. The rise in TMin at Rampur is predicted to be continued in future as increasing trends are obtained under both the scenarios. Seasonal trend analysis reveals large variability in trends of TMax and TMin over these stations for the future periods.

关键词： Statistical downscaling model Canadian Coupled Global Climate Model Temperature MannKendall test Sen’s slope estimator

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Preface to the Special Issue:Aerosols,Clouds,Radiation,Precipitation,and Their Interactions

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Advances in Atmospheric Sciences 2018年第2期35卷 133-134页

作者： Xiquan DONG Institute of Heavy Rain China Meteorological AdministrationHubei Key Laboratory for Heavy Rain Monitoring and Warning Research department of hydrology and Atmospheric Sciences University of Arizona

The treatment of aerosols, clouds, radiation, and precipitation in climate models, in addition to their interactions and as- sociated feedbacks, has long been one of the largest sources of uncertainty in predicting any potential future climate changes. Although many improvements have been made in CMIP5, aerosols, clouds, radiation, and their feedbacks are still a problem in climate models, as concluded in IPCC AR5 and published papers. Many studies have shown that modeled aerosols, clouds, radiation, and precipitation agree with observations within a certain range on a global scale; however, large biases occur at the regional scale. Characterizing the effects of aerosols and clouds on energy and the hydrological cycle and understanding the interactions among aerosols, clouds, radiation, and precipitation, are critical for weather forecasting and climate models. Significant improvements are needed, which require advanced observations and modeling at a range of spatial and temporal scales.

关键词： Preface to the Special Issue Aerosols Clouds Radiation Precipitation

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Statistical description of depth-dependent turbulent velocity measured in Taihu Lake, China

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Water Science and Engineering 2018年第3期11卷 243-249页

作者： Lin Yuan Hong-guang Sun Yong Zhang Yi-ping Li Bing-qing Lu State Key Laboratory of hydrology-Water Resources and Hydraulic Engineering Hohai University College of Mechanics and Materials Hohai University department of Geological Sciences University of Alabama College of Environment Hohai University

Quantitative description of turbulence using simple physical/mathematical models remains a challenge in classical physics and hydrologic dynamics. This study monitored the turbulence velocity field at the surface and bottom of Taihu Lake, in China, a large shallow lake with a heterogeneous complex system, and conducted a statistical analysis of the data for the local turbulent structure. Results show that the measured turbulent flows with finite Reynolds numbers exhibit properties of non-Gaussian distribution. Compared with the normal distribution, the Levy distribution with meaningful parameters can better characterize the tailing behavior of the measured turbulence. Exit-distance statistics and multiscaling extended self-similarity(ESS) were used to interpret turbulence dynamics with different scale structures. Results show that the probability density function of the reverse structure distance and the multiscaling ESS can effectively capture the turbulent flow dynamics varying with water depth. These results provide an approach for quantitatively analyzing multiscale turbulence in large natural lakes.

关键词： Finite Reynolds number turbulence Reverse structure function Levy distribution Probability density function Multiscaling extended self-similarity(ESS)

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Temporal variations of sediment and morphological characteristics at a large confluence accounting for the effects of floodplain submergence

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International Journal of Sediment Research 2022年第5期37卷 619-638页

作者： Kun Li Hongwu Tang Saiyu Yuan Lei Xu Yang Xiao Carlo Gualtieri State Key Laboratory of hydrology-Water Resources and Hydraulic Engineering Hohai University Yangtze Institute for Conservation and Development department of Structures for Engineering and Architecture University of Napoli Federico Ⅱ

The large confluence between the Yangtze River and the outflow channel of Poyang Lake is receiving attention due to its importance in flood control and ecological protection in the Yangtze River *** is a large floodplain along the outflow channel of Poyang Lake, which is submerged during high flow and dry during low flow. The effects of the submergence of this floodplain on sediment and morphological characteristics at this large confluence have not been known. Hence, a field investigation was done in March 2019(relatively high flow, Survey 3) to complement the previous field studies done in August(high flow, Survey 1) and December 2018(low flow, Survey 2) to identify the temporal variations of sediment and morphological characteristics considering the submergence of this large floodplain. The predominant sediment transport modes were wash load for Poyang Lake and confluence particles and mixed bedload/suspended load for the Yangtze River particles. The sediment transport processes were largely affected by both the secondary flows and the water density contrast between the tributaries with a lock-exchange sediment rich, denser flow moving across the inclined mixing interface in Surveys 1 and 2. The sediment flux across the mixing interface was weakened in Survey 3 when the density contrast was very small. The stagnation zone near the confluence apex had a low sediment concentration and played a role in preventing the sediment flux exchange between the two flows, and its size, and, thus, its importance as a barrier to sediment mixing were related to the submergence of the floodplain. The bed morphology with the local scour holes at the confluence was largely affected by the large-size helical cells, and this kind of effect was weakened as the secondary flows got restricted in Survey 3. The current results expand the database and knowledge on the sediment transport and morphological features of large river confluences.

关键词： River confluence Yangtze river Poyang lake Compound channel Sediment transport Morphodynamics

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Effect of Triisopropanolamine on the Compressive Strength and Early Hydration of Cement at Low Temperature

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Journal of Wuhan University of Technology(Materials Science) 2020年第3期35卷 611-619页

作者： ZHANG Feng BAI Yin CAI Yuebo CHEN Bo NING Fengwei State Key Laboratory of hydrology-Water Resources and Hydraulic Engineering Nanjing Hydraulic Research InstituteNanjing 210029China

Triisopropanolamine (TIPA) was used as an early strength component to study its effects on mortar strength, cement paste setting time and early hydration characteristic of cement. And the early strength mechanism of TIPA at low temperature of 5 ℃ was also discussed. The results showed that, at 5 ℃, the incorporation of TIPA promoted the condensation of cement paste, shortened the initial and final setting time, and accelerated the strength development of specimens at all ages, among which the strength after 3 d increased significantly. The 1, 3, 7, and 28 d compressive strength ratios of the mortars mixed with 1% TIPA could reach 196%, 179%, 160% and 110% respectively, and the mortar strength after 3 d exceeded that of the contrast sample cured at 20 ℃. Under low temperature condition, TIPA could promote the hydration reaction of cement, shorten the induction period and advance the acceleration period. Furthermore, the maximum heat release rate and cumulative heat release quantity would be all increased, and the cumulative heat release of the cement mixed with TIPA hydrated for 12 h and 7 d increased 73% and 38% respectively. TIPA could shorten the nucleation and crystal growth (NG) stage and increase its hydration degree significantly, so it promoted cement hydration reaction. Additionally, the hydration reaction rates in phase boundary reaction (I) phase and diffusion reaction (D) phase were increased, and the duration of I process was prolonged, thereby the development of specimen strength would be accelerated. TIPA did not obviously change the types of hydration products, but increased the content of Ca(OH)2 in the samples and the degree of cement hydration. After hydration to 7 d, large amounts of hydration products, whose surface was smooth, were formed and bonded into sheets, and the structural density of samples improved significantly.

关键词： low temperature triisopropanolamine compressive strength hydration mechanism

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Modeling the Water-Flushing Properties of the Yangtze Estuary and Adjacent Waters

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Journal of Ocean University of China 2019年第1期18卷 93-107页

作者： YANG Jie KONG Jun TAO Jianfeng College of Harbour Coastal and Offshore Engineering Hohai University department of Civil and Environmental Engineering National University of Singapore State Key Laboratory of hydrology-Water Resources and Hydraulic Engineering Hohai University

As a multi-branch estuary system, the Yangtze Estuary presents distinctive characteristics of hydrodynamic processes through co-action among river runoff, tides, wind-waves, and gravitational circulation. To study the pathways of flushing water along all of the estuary's branches and analyze their differences, especially those due to the influence of seawater intrusion and discharge variations, a free surface flow modeling suite TELEMAC-MASCARET involving passive tracers was applied to the Yangtze Estuary and the adjacent waters. The open boundary conditions were provided by the Nao.99 b model(Matsumoto et al., 2000), which was calibrated using observed velocity and salinity data obtained in March 2002. The water age, which was used as the diagnostic tool to study the flushing efficiency of the water body across the estuary, was solved by additional advection-diffusion-reaction equations implemented in the TELEMAC modeling system. The transport properties were investigated under different river discharge scenarios, which represented seasonal impacts; aspects relating to the influence of tide, surface wind stress, and density-induced circulation on age were also investigated. Model results showed that river runoff is one of the dominant factors influencing the spatial distribution of the mean age, while tidal force is another important factor. The horizontal freshwater age distribution demonstrated similarity compared with the salinity distribution; the vertical age distribution resembled the stratification pattern of salinity in all branches where stratification persists. An experimental numerical simulation of tracing saltwater age from the lower reaches of the estuary was conducted, and implicated the connectivity with transport processes of freshwater from upstream. Additionally, a particle tracking algorithm was used to analyze the dynamic characteristics of the four passages. The South Passage and South Channel were found to be significant as main water flow pa

关键词： water age seawater intrusion the Yangtze Estuary numerical modeling particle tracking algorithm

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Mapping of Freshwater Lake Wetlands Using Object-Relations and Rule-based Inference

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Chinese Geographical Science 2012年第4期22卷 462-471页

作者： RUAN Renzong Susan USTIN State Key Laboratory of hydrology-Water Resources and Hydraulic Engineering Hohai University Nanjing 210098 China department of Land Air and Water Resources University of California Davis CA 95616 the United States)

Inland freshwater lake wetlands play an important role in regional ecological balance. Hongze Lake is the fourth biggest freshwater lake in China. In the past three decades, there has been significant loss of freshwater wet- lands within the lake and at the mouths of neighboring rivers, due to disturbance, primarily from human activities. The main purpose of this paper was to explore a practical technology for differentiating wetlands effectively from upland types in close proximity to them. In the paper, an integrated method, which combined per-pixel and per-field classifi- cation, was used for mapping wetlands of Hongze Lake and their neighboring upland types. Firstly, Landsat ETM＋ imagery was segmented and classified by using spectral and textural features. Secondly, ETM＋ spectral bands, textural features derived from ETM＋ Pan imagery, relative relations between neighboring classes, shape fea^xes, and elevation were used in a decision tree classification. Thirdly, per-pixel classification results from the decision tree classifier were improved by using classification results from object-oriented classification as a context. The results show that the technology has not only overcome the salt-and-pepper effect commonly observed in the past studies, but also has im- proved the accuracy of identification by nearly 5%.

关键词： rule-based inferring object-based classification freshwater lake wetland relation feature Hongze Lake

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Evaluating methods to quantify sediment volumes trapped behind check dams,Saldana badlands(Spain)

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International Journal of Sediment Research 2017年第1期32卷 1-11页

作者： Iván Ramos-Diez Joaquín Navarro-Hevia Roberto San Martín Fernández Virginia Díaz-Gutiérrez Jorge Mongil-Manso department of Agricultural and Forestry Engineering University of Valladolid Sustainable Forest Management Research Institute department of Statistics and Operations Research.University of Valladolid hydrology and Conservation Research Group.Catholic University of vila

The determination of sediment yield in catchments based on the sediment trapped by check dams is becoming a subject of *** fact,several methods have been developed in recent years to estimate the sediment retained by check *** complexity,precision and accuracy of each method vary *** this study,we evaluate the sediment trapped by check dams comparing the Sections method respect to the Prism,Pyramid,DTMs and Trapezoid *** analyzed a sample of 25 check dams(α-1=90%;ε=10%) in the Saldana badlands(Spain).The results showed that the Sections method offered a volume of retained sediment between the others,which gave an absolute variation from 22%to40%.The high variability of the check dam and sediment wedge sizes made necessary to compare methods in groups combining both *** significant differences in sediment volumes could be found between the methods for very small(height(h):1.8-2.3 m;trapped volume(V):6-102 m3) or large check dams(h > 2.3 m;V:165-387 m3),while significant differences are found for small(h < 1.5 m;V:1-229 m3) or middle-sized check dams(h:2.2-3.2 m;V:65-235 m3).Nevertheless,volume differences between groups ranged up to + 25%.For these reason,the size of the check dam,the shape of the sediment wedge and the accuracy of the measure methods must considered when selecting an appropriate method to obtain the volume of retained sediment by check dams.A correct estimation of the sediment retention is needed to evaluate the role and efficiency of check dams in restoration projects or to estimate sediment yields.

关键词： Erosion Gullies Check dam construction Sediment retention Erosion models Topographic survey

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Numerical Study of A Round Buoyant Jet Under the Effect of JONSWAP Random Waves

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China Ocean Engineering 2012年第2期26卷 235-250页

作者：陈永平李志伟张长宽徐振山 State Key Laboratory of hydrology-Water Resources and Hydraulic Engineering Hohai University College of Harbor Coastal and Offshore EngineeringHohai University department of Civil and Structural Engineering The Hong Kong Polytechnic University

This paper presents a numerical study on the hydrodynamic behaviours of a round buoyant jet under the effect of JONSWAP random waves. A three-dimensional large eddy simulation （LES） model is developed to simulate the buoyant jet in a stagnant ambient and JONSWAP random waves. By comparison of velocity and concentration fields, it is found that the buoyant jet exhibits faster decay of centerline velocity, wider lateral spreading and larger initial dilution under the wave effect, indicating that wave dynamics improves the jet entrainment and mixing in the near field, and subsequently mitigate the jet impacts in the far field. The effect of buoyancy force on the jet behaviours in the random waves is also numerically investigated. The results show that the wave effect on the jet entrainment and mixing is considerably weakened under the existence of buoyancy force, resulting in a slower decay rate of centerline velocity and a narrower jet width for the jet with initial buoyancy.

关键词： numerical study large eddy simulation buoyant jet JONSWAP random waves

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Drought monitoring and reliability evaluation of the latest TMPA precipitation data in the Weihe River Basin, Northwest China

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Journal of Arid Land 2017年第2期9卷 256-269页

作者： JIANG Shanhu REN Liliang ZHOU Meng YONG Bin ZHANG Yu MA Mingwei State Key Laboratory of hydrology-Water Resources and Hydraulic Engineering Hohai University department of Civil and Environmental Engineering Princeton University School of Water Conservancy North China University of Water Resources and Electric Power

The high resolution satellite precipitation products bear great potential for large-scale drought monitoring, especially for those regions with sparsely or even without gauge coverage. This study focuses on utilizing the latest Version-7 TRMM Multi-satellite Precipitation Analysis （TMPA 3B42V7） data for drought condition monitoring in the Weihe River Basin （0.135×10^6 km2）. The accuracy of the monthly TMPA 3B42V7 satellite precipitation data was firstly evaluated against the ground rain gauge observations. The statistical characteristics between a short period data series （1998-2013） and a long period data series （1961-2013） were then compared. The TMPA 3B42V7-based SPI （Standardized Precipitation Index） sequences were finally validated and analyzed at various temporal scales for assessing the drought conditions. The results indicate that the monthly TMPA 3B42V7 precipitation is in a high agreement with the rain gauge observations and can accurately capture the temporal and spatial characteristics of rainfall within the Weihe River Basin. The short period data can present the characteristics of long period record, and it is thus acceptable to use the short period data series to estimate the cumulative probability function in the SPI calculation. The TMPA 3B42V7-based SPI matches well with that based on the rain gauge observations at multiple time scales （i.e., 1-, 3-, 6-, 9-, and 12-month） and can give an acceptable temporal distribution of drought conditions. It suggests that the TMPA 3B42V7 precipitation data can be used for monitoring the occurrence of drought in the Weihe River Basin.

关键词： TMPA satellite precipitation drought monitoring SPI Weihe River Basin

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