A geomorphologic kinematic‐wave (GKW) model for estimation of floods from small alpine watersheds     

Dominique D. Brod  Vijay P. Singh  Andre Musy 《水文研究》1999,13(9):1391-1416

A geomorphologic kinematic‐wave (GKW) model was developed for simulation of extreme floods from small alpine catchments. The GKW model couples the kinematic‐wave theory and the geomorphologic representation of the catchment based on the Horton–Strahler ordering scheme. The model was tested on two small alpine catchments in Switzerland, and the agreement between simulated and observed floods was good. Care must however be taken with the computation of slope and roughness parameters. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   

Recent Trends of Arctic and Antarctic Summer Sea-Ice Cover Observed from Space-Borne Scatterometer     

Sandip R. Oza  R. K. K. Singh  N. K. Vyas  Abhijit Sarkar 《Journal of the Indian Society of Remote Sensing》2010,38(4):611-616

Long term variations in Sea ice distribution strongly influence the atmosphere and ocean in the polar regions. In the recent period significant variations in sea ice cover have been observed in both the hemispheres. In the past, studies have been carried out that report the trends either at the Arctic/Antarctic level or at sector level. However, only a few studies have concentrated on the investigation of trends at grid level using scatterometer data. The present study focuses on the investigations of the sea ice trend at 1 × 1 degree grid level over the period 2000–2007 using QuickSCAT 0.2-degree resolution Scatterometer data. It was observed that in the Arctic overall monthly trend is negative in all the sectors, with the Arctic level decline of 3.26% per year. In the Antarctic, region-wise different trends have been observed. Negative trend is observed in the Amundsen- Bellingshausen Seas and also in the Indian Ocean sector near the continental Ice shelves. It was highlighted that significant trends exists within the pockets of marginal seas.  相似文献   

Fluid Institutions: Commons in Transition in the Periurban Interface     

Aditya Kumar Singh  Vishal Narain 《社会与自然资源》2019,32(5):606-615

Amidst growing concern about the decline of the commons, this case underscores the importance of understanding how the commons are refashioned and remade to address emerging challenges in periurban spaces. This article describes how institutions surrounding the use of common property resources get transformed and evolve in periurban contexts. What were once johads – common property village ponds – undergo a change in their usage from storing rainwater to storing waste water of the city for irrigation. This emerges as a collective response to the uncertainty attached to the availability of waste water. New institutions evolve with regard to contributions to waste water infrastructure, as well as the appropriation of waste water. Further research should document the changing use of village commons and the emergence of new institutions governing them.  相似文献   

Hyper-spectral data based investigations for snow wetness mapping     

Chander Shekhar  Sunita Srivastava  Harendra Singh Negi  Manish Dwivedi 《国际地球制图》2019,34(6):664-687

Spatial information on snow wetness content (SWC) is important for hydrology, climatology applications. Limited work is available on estimation of SWC using optical sensors. In present work, spectral signature characteristics of snow (~145 samples) acquired in winters of three years, using field spectral-radiometer (350–2500 nm) were correlated with synchronized SWC measurements. Correlation is found stronger in Near-Infra-Red (NIR) and Short-Wave-Infrared (SWIR) regions than Visible (VIS). Spectral peak width at 905 and 1240 nm is found negatively correlated with SWC, while positively correlated at 1025 nm. Asymmetry tends towards right as SWC increases and has stable positive correlations as compared to other characteristics. Sensitivity of widely used snow-related indices to SWC is also analyzed. Based on analysis, new ratio method at selected wavelengths is proposed to discriminate dry and wet snow zones using air/ground borne sensors. Proposed methodology is evaluated on air-borne hyper-spectral (AVIRIS-NG) data and 88% overall accuracy with kappa coefficient 77.6 observed after validation with reference observations.  相似文献   

Assessment of glacier stored water in Karakoram Himalaya using satellite remote sensing and field investigation     

Kamal Kant SINGH  Harendra Singh NEGI  Dhiraj Kumar SINGH 《山地科学学报》2019,(4)

Karakoram Himalaya(KH) has continental climatic conditions and possesses largest concentration of glaciers outside the polar regions. The melt water from these glaciers is a major contributor to the Indus river. In this study, various methods have been used to estimate the ice volume in the Karakoram Range of glaciers such as Coregistration of Optically Sensed Images and Correlation(COSI-Corr) method and Area-Volume relations. Landsat 8 satellite data has been used to generate the ice displacement, velocity and thickness map. Our study for 558 Karakoram glaciers revealed that the average ice thickness in Karakoram is 90 m. Ground Penetrating Radar(GPR) survey has been conducted in one of the KH glacier i.e. Saser La glacier and the collected GPR data is used for the validation of satellite derived thickness map. GPR measured glacier thickness values are found comparable with satellite estimated values with RMSE of 4.3 m. The total ice volume of the Karakoram glaciers is estimated to be 1607±19 km3(1473±17 Gt), which is equivalent to 1473±17 km3 of water equivalent. Present study also covers the analysis of glacier surface displacement, velocity and ice thickness values with reference to glacier mean slope.  相似文献   

Shock‐thermal history of the Agoudal (IIAB) iron meteorite from microstructural studies     

D. Ray  S. Ghosh  H. Chennaoui Aoudjehane  S. Das 《Meteoritics & planetary science》2019,54(12):3082-3088

The Agoudal IIAB iron meteorite exhibits only kamacite grains (~6 mm across) without any taenite. The kamacite is homogeneously enriched with numerous rhabdite inclusions of different size, shape, and composition. In some kamacite domains, this appears frosty due to micron‐scale rhabdite inclusions (~5 to 100 μm) of moderate to high Ni content (~26 to 40 wt%). In addition, all the kamacite grains in matrix are marked with a prominent linear crack formed during an atmospheric break‐up event and subsequently oxidized. This feature, also defined by trails of lowest Ni‐bearing (mean Ni: 23 wt%) mm‐scale rhabdite plates (fractured and oxidized) could be a trace of a pre‐existing γ–α interface. Agoudal experienced a very slow rate of primary cooling ~4 °C Ma^?1 estimated from the binary plots of true rhabdite width against corresponding Ni wt% and the computed cooling rate curves after Randich and Goldstein (1978). Chemically, Agoudal iron (Ga: 54 ppm; Ge: 140 ppm; Ir: 0.03 ppm) resembles the Ainsworth iron, the coarsest octahedrite of the IIAB group. Agoudal contains multiple sets of Neumann bands that are formed in space and time at different scales and densities due to multiple impacts with shock magnitude up to 130 kb. Signatures of recrystallization due to postshock low temperature mild reheating at about 400 °C are also locally present.  相似文献   

Assessing the spatiotemporal distributions of evapotranspiration in the Three Gorges Reservoir Region of China using remote sensing data     

Ze-zhong Ma  Ram L Ray  Yi-ping He 《山地科学学报》2018,15(12):2676-2692

Evapotranspiration (ET) is a critical component of the global hydrological cycle, and it has a large impact on water resource management as it affects the availability of freshwater resources. It is important to understand the hydrological cycle for the water resources planning and management. This study used Moderate Resolution Imaging Spectroradiometer (MODIS) satellite derived ET, and potential evapotranspiration (PET) and Tropical Rainfall Measuring Mission (TRMM) satellite derived precipitation datasets to assess the spatial and temporal distributions of ET, PET, and precipitation during the study period at Three Gorges Reservoir (TGR) region. Based on the topographic variations and land-use/land-cover distributions, the study region which includes five counties of Hubei Province and nineteen counties of Chongqing Municipality was divided into four study zones. The ET and precipitation data were evaluated using in situ observations. The ET, PET, and precipitation data were compared to analyze the spatial and long-term (2001-2016) temporal distributions of average annual ET, PET, and precipitation, and to understand the relationships between them in the study region. The results showed that each selected zone had highest ET at the counties with the Yangtze River passing through whereas lowest at the counties which were located away from the river. Results also showed increasing trends in ET and PET from south-west to north-east in the study region. Analysis showed TGR had a significant impact on spatial and temporal distributions of ET and PET in the study region. Therefore, this study helps to understand the impact of TGR on spatial and temporal distributions of ET and PET during and after the construction.  相似文献   

Mapping of rock types using a joint approach by combining the multivariate statistics,self-organizing map and Bayesian neural networks: an example from IODP 323 site     

Mampi Karmakar  Saumen Maiti  Amrita Singh  Maheswar Ojha  Bhabani Sankar Maity 《Marine Geophysical Researches》2018,39(3):407-419

Modeling and classification of the subsurface lithology is very important to understand the evolution of the earth system. However, precise classification and mapping of lithology using a single framework are difficult due to the complexity and the nonlinearity of the problem driven by limited core sample information. Here, we implement a joint approach by combining the unsupervised and the supervised methods in a single framework for better classification and mapping of rock types. In the unsupervised method, we use the principal component analysis (PCA), K-means cluster analysis (K-means), dendrogram analysis, Fuzzy C-means (FCM) cluster analysis and self-organizing map (SOM). In the supervised method, we use the Bayesian neural networks (BNN) optimized by the Hybrid Monte Carlo (HMC) (BNN-HMC) and the scaled conjugate gradient (SCG) (BNN-SCG) techniques. We use P-wave velocity, density, neutron porosity, resistivity and gamma ray logs of the well U1343E of the Integrated Ocean Drilling Program (IODP) Expedition 323 in the Bering Sea slope region. While the SOM algorithm allows us to visualize the clustering results in spatial domain, the combined classification schemes (supervised and unsupervised) uncover the different patterns of lithology such of as clayey-silt, diatom-silt and silty-clay from an un-cored section of the drilled hole. In addition, the BNN approach is capable of estimating uncertainty in the predictive modeling of three types of rocks over the entire lithology section at site U1343. Alternate succession of clayey-silt, diatom-silt and silty-clay may be representative of crustal inhomogeneity in general and thus could be a basis for detail study related to the productivity of methane gas in the oceans worldwide. Moreover, at the 530 m depth down below seafloor (DSF), the transition from Pliocene to Pleistocene could be linked to lithological alternation between the clayey-silt and the diatom-silt. The present results could provide the basis for the detailed study to get deeper insight into the Bering Sea’ sediment deposition and sequence.  相似文献   

Three-dimensional velocity measurements around bridge piers in gravel bed     

Manish Pandey  P. K. Sharma  Z. Ahmad  Umesh Kumar Singh  Nilav Karna 《Marine Georesources & Geotechnology》2018,36(6):663-676

The experimental results of time average velocity components measured around circular pier models during transient scour stage using acoustic Doppler velocimeter are shown for flow pattern and turbulence characteristics. Totally, four experiments were performed under clear water scour conditions in a model of gravel bed stream. Four circular pier models of diameter 6.6, 8.4, 11.5, and 13.5?cm were used for this study. Detailed controlled measurements on velocity components, and turbulence intensities near the pier and in scour hole at 0° and 180° plane are shown. Flow structure around a pier model in the presence of a scoured region was compared with the flow structure similarly noticed around all pier model runs by utilizing the observations taken at 0° and 180° plane from flow axis. Size of the primary vortex at 0° plane with largest diameter pier model in place (R4 run) is found to be maximum and was approximately 61% larger than that for smallest diameter pier model in place (R1 run). The time-averaged velocity components of turbulence intensities plots at 0° and 180° planes are also presented around each pier.  相似文献   

A quantum chemical study on the formation of ethanimine (CH<Subscript>3</Subscript>CHNH) in the interstellar ice     

Keshav Kumar Singh  Shivani  Poonam Tandan  Alka Misra 《Astrophysics and Space Science》2018,363(10):213

Ethanimine (CH₃CHNH) is an important prebiotic molecule since it is a precursor of amino acid \(\alpha \)-alanine in Strecker synthesis. Two isomers (E and Z) of ethanimine were detected in the molecular cloud Sagittarius B2 north during GBT-PRIMOS survey. A possible radical-molecule reaction pathway has been proposed for the formation of ethanimine in the interstellar medium (ISM) from some previously detected interstellar molecules like methylene (both triplet CH₂ (³B₁) and singlet CH₂ (¹A₁)) and methyenimine (CH₂NH). The mechanism has been studied in the gas phase and in water ice with the help of density functional theory at B2PLYPD/6-311++G (2d, p) level of theory. It is observed that E-ethanimine forms efficiently in gas phase but ice reactions are favorable only in the hot core of molecular clouds. Same is true for the formation of Z-ethanimine which forms only at the surface of water cluster as the height of entrance barrier for formation of Z-ethanimine is similar to that of E-ethanimine. Isomerization from E to Z form is also studied and found to be forbidden due to large entrance barrier. Out of the two reaction system CH₂ (³B₁) + CH₂NH and CH₂ (¹A₁) + CH₂NH, later is more favorable then the former one due to the small entrance barrier. Still, much of the detected abundance of ethanimine comes from the reaction of CH₂ (³B₁) with CH₂NH as since CH₂ (¹A₁) has very low abundance compared to the CH₂ (³B₁) in ISM. The proposed pathway seems to be a promising candidate for the ethanimine formation in ISM.  相似文献