State Key Laboratory of Hydroscience and Engineering
State Key Laboratory of Hydroscience and Engineering
Tang G.,State Key Laboratory of Hydroscience and Engineering |
Wen Y.,Jet Propulsion LaboratoryCalifornia Institute of TechnologyPasadena |
Gao J.,State Key Laboratory of Hydroscience and Engineering |
Long D.,State Key Laboratory of Hydroscience and Engineering |
And 2 more authors.
Water Resources Research | Year: 2017
Precipitation is one of the most important components in the water and energy cycles. Radars are considered the best available technology for observing the spatial distribution of precipitation either from the ground since the 1980s or from space since 1998. This study, for the first time ever, compares and evaluates the only three existing spaceborne precipitation radars, i.e., the Ku-band precipitation radar (PR), the W-band Cloud Profiling Radar (CPR), and the Ku/Ka-band Dual-frequency Precipitation Radar (DPR). The three radars are matched up globally and intercompared in the only period which they coexist: 2014-2015. In addition, for the first time ever, TRMM PR and GPM DPR are evaluated against hourly rain gauge data in Mainland China. Results show that DPR and PR agree with each other and correlate very well with gauges in Mainland China. However, both show limited performance in the Tibetan Plateau (TP) known as the Earth's third pole. DPR improves light precipitation detectability, when compared with PR, whereas CPR performs best for light precipitation and snowfall. DPR snowfall has the advantage of higher sampling rates than CPR; however, its accuracy needs to be improved further. The future development of spaceborne radars is also discussed in two complementary categories: (1) multifrequency radar instruments on a single platform and (2) constellations of many small cube radar satellites, for improving global precipitation estimation. This comprehensive intercomparison of PR, CPR, and DPR sheds light on spaceborne radar precipitation retrieval and future radar design. © 2017. American Geophysical Union. All Rights Reserved.
Li H.-Y.,Hydrology Technical Group |
Sivapalan M.,University of Illinois at Urbana - Champaign |
Tian F.,State Key Laboratory of Hydroscience and Engineering
Water Resources Research | Year: 2014
Inspired by the Dunne diagram, the climatic and landscape controls on the partitioning of annual runoff into its various components (Hortonian and Dunne overland flow and subsurface stormflow) are assessed quantitatively, from a purely theoretical perspective. A simple distributed hydrologic model has been built sufficient to simulate the effects of different combinations of climate, soil, and topography on the runoff generation processes. The model is driven by a sequence of simple hypothetical precipitation events, for a large combination of climate and landscape properties, and hydrologic responses at the catchment scale are obtained through aggregation of grid-scale responses. It is found, first, that the water balance responses, including relative contributions of different runoff generation mechanisms, could be related to a small set of dimensionless similarity parameters. These capture the competition between the wetting, drying, storage, and drainage functions underlying the catchment responses, and in this way, provide a quantitative approximation of the conceptual Dunne diagram. Second, only a subset of all hypothetical catchment/climate combinations is found to be “behavioral,“ in terms of falling sufficiently close to the Budyko curve, describing mean annual runoff as a function of climate aridity. Furthermore, these behavioral combinations are mostly consistent with the qualitative picture presented in the Dunne diagram, indicating clearly the commonality between the Budyko curve and the Dunne diagram. These analyses also suggest clear interrelationships amongst the “behavioral“ climate, soil, and topography parameter combinations, implying these catchment properties may be constrained to be codependent in order to satisfy the Budyko curve. © 2014. American Geophysical Union. All Rights Reserved.
Zhou S.,State Key Laboratory of Hydroscience and Engineering |
Wang G.,State Key Laboratory of Hydroscience and Engineering
Water Resources Research | Year: 2016
Evapotranspiration (ET) is dominated by transpiration (T) in the terrestrial water cycle. However, continuous measurement of transpiration is still difficult, and the effect of vegetation on ET partitioning is unclear. The concept of underlying water use efficiency (uWUE) was used to develop a new method for ET partitioning by assuming that the maximum, or the potential uWUE is related to T while the averaged or apparent uWUE is related to ET. T/ET was thus estimated as the ratio of the apparent over the potential uWUE using half-hourly flux data from 17 AmeriFlux sites. The estimated potential uWUE was shown to be essentially constant for 14 of the 17 sites, and was broadly consistent with the uWUE evaluated at the leaf scale. The annual T/ET was the highest for croplands, i.e., 0.69 for corn and 0.62 for soybean, followed by grasslands (0.60) and evergreen needle leaf forests (0.56), and was the lowest for deciduous broadleaf forests (0.52). The enhanced vegetation index (EVI) was shown to be significantly correlated with T/ET and could explain about 75% of the variation in T/ET among the 71 site-years. The coefficients of determination between EVI and T/ET were 0.84 and 0.82 for corn and soybean, respectively, and 0.77 for deciduous broadleaf forests and grasslands, but only 0.37 for evergreen needle leaf forests. This ET partitioning method is sound in principle and simple to apply in practice, and would enhance the value and role of global FLUXNET in estimating T/ET variations and monitoring ecosystem dynamics. © 2016. American Geophysical Union. All Rights Reserved.
Chen Y.,State Key Laboratory of Hydroscience and Engineering |
Yu X.,State Key Laboratory of Hydroscience and Engineering
Journal of Advances in Modeling Earth Systems | Year: 2017
The application of the wave boundary layer model (WBLM) for wind stress evaluation to storm wave modeling is studied using Hurricane Katrina (2005) as an example, which is chosen due to its great intensity and good availability of field data. The WBLM is based on the momentum and energy conservation equations and takes into account the physical details of air-sea interaction processes as well as energy dissipation due to the presence of sea spray. Four widely-used bulk-type formulas are also used for comparison. Simulated significant wave heights with WBLM are shown to agree well with the observed data over deep water. The WBLM yields a smaller wind stress coefficient on the left hand side of the hurricane track, which is reasonable considering the effect of the sea state on momentum transfer. Quantitative results show that large differences of the significant wave height are observed in the hurricane core among five wind stress evaluation methods and the differences are up to 12 m, which is in agreement with the general knowlege that the ocean dynamic processes under storm conditions are very sensitive to the amount of momentum exchange at the air-sea interface. However, it is the depth-induced energy dissipation, rather than the wind energy input, that dominates the wave height in the shallow water region. A larger value of depth-induced breaking parameter in the wave model results in better agreement with the measurements over shallow water. © 2017. The Authors.
Zhao S.,State Key Laboratory of Hydroscience and Engineering |
Yang D.,State Key Laboratory of Hydroscience and Engineering
Shuili Fadian Xuebao/Journal of Hydroelectric Engineering | Year: 2011
Neural network is one of the popular and effective models used for hydrological forecasting. One of the major problems of this method is the selection of input variables. This study focuses on this problem and uses the mutual information (MI) to select neural network input variables. Application to the daily discharge forecasting at the Yichang hydrological station before the Three Gorges project shows that MI is an effective technique for selecting the input variables and thus for improving the runoff forecasting accuracy. © Copyright.
Zhou J.,State key Laboratory of Hydroscience and Engineering |
Zhang M.,State key Laboratory of Hydroscience and Engineering |
Lin B.,State key Laboratory of Hydroscience and Engineering |
Lu P.,Water Environment Monitoring Center for the Upper Reach of Yangtze River
Water Resources Research | Year: 2015
Dams affect ecosystems, but their physical link to the variations in fluvial fluxes and downstream ecological consequences are inadequately understood. After estimating the current effects of the Three Gorges project and other reservoirs upstream on the Yangtze River on the fluvial phosphorus (P) in the middle and lower Yangtze River, we further investigated the long-term effects of dams on the fluvial regimes of P and P-enriched sediment (PES). Simultaneously measured P distributions with sediment size (PDSS) from the Three Gorges Reservoir (TGR) proved that the areal density of particulate P (PP) bound on graded sediment can be measured using the surface area concentration of the total sediment. A PDSS relationship is obtained and the selective transport and long-term sedimentation of P are simulated using a nonuniform suspended sediment model, which incorporates the PDSS formula. The computations revealed that a reservoir would significantly lower the downstream availability of P in the dry season and promote high pulses of P in summer when the reservoir is flushed as sedimentation accumulates. As a result, the P buffering and replenishing mechanism in the pristine ecosystem from upstream supplies and local re-suspension are permanently eliminated when a regulating reservoir is built upstream. This change is irreversible if reservoir regulation continues. Changes could potentially aggravate the existing P-limitation, decrease the water's ability to adjust nutrient/pollutant fluctuations, accumulate a greater surplus of carbon and nitrogen, and even exacerbate blooms in favorable conditions. © 2015. American Geophysical Union. All Rights Reserved.
Li H.-Z.,Central Research Institute of Building and Construction |
Hu L.-M.,Tsinghua University |
Hu L.-M.,State Key Laboratory of Hydroscience and Engineering |
Xin H.-B.,Central Research Institute of Building and Construction
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2015
The groundwater pollution by organic contaminants is becoming more and more severe, making groundwater remediation be imperative. The researches on the remediation technology are of theoretical and practical importance. Based on the review of in-situ groundwater remediation technology for organic contaminants and micro-nano bubble MNBs technology, MNB technology is proposed for groundwater remediation. The scheme using MNB for in-situ groundwater remediation is introduced. The contaminants can be removed by biodegradation enhanced by MNB. The numerical simulation results of in-situ application show a great enhancement on dissolved oxygen and a significant influence zone for contaminant removal. The MNB technology is effective, energy-efficient and environment-friendly to clean up contaminants, which has great potential in groundwater remediation. ©, 2015, Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering. All right reserved.
Feng D.-K.,State Key Laboratory of Hydroscience and Engineering |
Feng D.-K.,Tsinghua University |
Hou W.-J.,Ministry of Housing and Urban Rural Development of the Peoples Republic of China |
Zhang J.-M.,State Key Laboratory of Hydroscience and Engineering |
Zhang J.-M.,Tsinghua University
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2011
A new apparatus is developed to investigate the stress-controlled behavior of the interface between structure and gravelly soil under constant normal stiffness condition. The test results indicate that: (1) the volumetric change is induced by cyclic shear and can be divided into reversible and irreversible parts. The reversible part is governed by tangential displacement amplitude, and the irreversible part is significantly affected by shear distance; (2) the anisotropy of interface volumetric change is obviously observed and has great concern with shear paths and control modes; (3) the tangential displacement accumulates and migrates gradually with shear cycles. The shear paths and control modes have influences on the relationship between shear stress, stress ratio, normal displacement versus tangential displacement; (4) the interface shear strength is gradually mobilized after the first few shear cycles under stress control, and its friction angle is independent of the control modes.
Niu X.,State Key Laboratory of Hydroscience and Engineering |
Yu X.,Tsinghua University
Wave Motion | Year: 2011
An analytical solution of the mild-slope wave equation is derived to describe long wave propagating over the idealized dredge excavation pit. The pit is assumed to be axisymmetrical and composed of a flat bottom and a convex slope. The convex slope is expressed by a simple power function. The problem is solved in the polar coordination system by the separation of variables. By the obtained solution, the characteristics of the wave refraction and reflection over the dredge excavation pit are discussed. The results show that wave amplitude is attenuated within and in the lee side of the pit and amplified at the rear flank of the pit due to wave refraction. The effects of the incident wave length and the shape of the pit on wave refraction are also discussed. © 2010 Elsevier B.V.
PubMed | Nanjing Medical University, Qingdao Institute of Animal Science and Veterinary Medicine, Qingdao Agricultural University and State key Laboratory of Hydroscience and Engineering
Type: | Journal: BMC genetics | Year: 2015
Sheep are valuable resources for the animal fibre industry. Therefore, identifying genes which regulate wool growth would offer strategies for improving the quality of fine wool. In this study, we employed Agilent sheep gene expression microarray and proteomic technology to compare the gene expression patterns of the body side (hair-rich) and groin (hairless) skins of Aohan fine wool sheep (a Chinese indigenous breed).Comparing the body side to the groin skins (S/G) of Aohan fine wool sheep, the microarray study revealed that 1494 probes were differentially expressed, including 602 more highly expressed and 892 less highly expressed probes. The microarray results were verified by means of quantitative PCR. Cluster analysis could distinguish the body side skin and the groin skin. Based on the Database for Annotation, Visualization and Integrated Discovery (DAVID), 38 of the differentially expressed genes were classified into four categories, namely regulation of receptor binding, multicellular organismal process, protein binding and macromolecular complex. Proteomic study revealed that 187 protein spots showed significant (p < 0.05) differences in their respective expression levels. Among them, 46 protein entries were further identified by MALDI-TOF/MS analyses.Microarray analysis revealed thousands of differentially expressed genes, many of which were possibly associated with wool growth. Several potential gene families might participate in hair growth regulation. Proteomic analysis also indentified hundreds of differentially expressed proteins.