Glacier surface characteristics derivation and monitoring using Hyperspectral datasets: a case study of Gepang Gath glacier,Western Himalaya     

Akshay Gore  Sneh Mani  HariRam R.P.  Chander Shekhar  Ashwagosha Ganju 《国际地球制图》2019,34(1):23-42

Mountain Glaciers are natural resources of fresh water and these affect the stream flow of the rivers, regional climate and further global climate. Observed trends and projected future evolutions of climate and Cryospheric variables clearly suggest a need to monitor these changes. Accordingly, the article presents the glacier features mapping using Hyperspectral remote sensing imagery. A freely available Hyperion satellite imagery acquired over Gepang Gath glacier in Himachal Pradesh, India is used for the study. Each class is identified based on their surface characteristics of spectral reflectance properties. Identification is simplified by demarcating the study glacier into accumulation and ablation areas through snowline. Accumulation area is characterized with high reflectance clean snow/ice and reduced moderate reflectance Snow/firn. The identification of classes in Hyperion imagery is validated using the spectral library from USGS and ASTER, and field spectra obtained from literature.  相似文献   

Dynamical friction and the escape of a compact supermassive object shot from the center of a galaxy     

Ramesh Chander Kapoor 《Astrophysics and Space Science》1985,117(2):363-373

A numerical study has been made of the motion of a compact object consisting of a supermassive black hole with a dense cluster of stars around through a galaxy which has recoiled from the center of the latter as a result of anisotropic emission of gravitational radiation or asymmetrical plasma emission. We find that the effect of dynamical friction on its motion through the galaxy (mass10¹¹ M ) estimated using the impulsive approximation technique, is minimal for an object mass 10⁹ M and for recoil taking place at a velocity larger than that of escape. A velocity 1.1 times the escape velocity is needed for the object to escape from the galaxy, whereas for velocities of recoil less than this critical velocity, damped oscillatory motion ensures. The energy exchange of the object with the galaxy is not large enough to cause appreciable change in the internal energy of the latter.  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   

Geospatial modelling for sub-watershed prioritization in Western Himalayan Basin using morphometric parameters     

Shivhare  Vikash  Gupta  Chanchal  Mallick  Javed  Singh  Chander Kumar 《Natural Hazards》2022,110(1):545-561

Natural Hazards - Geographical information system and remote sensing are proven to be an efficient tool for locating water harvesting and recharge structures, groundwater potential, runoff,...  相似文献   

Ice Height and Backscattering Coefficient Variability over Greenland Ice Sheets Using SARAL Radar Altimeter     

S. Chander  S. K. Mishra  Prakash Chauhan  Ajai 《Marine Geodesy》2015,38(3):466-476

Ice sheets investigation is important with regard to climate change and contribution to the sea level rise or fall. Radar altimetry in complement with laser altimetry can serve as a suitable candidate for precise monitoring of ice sheet evaluations. SARAL due to higher observation into the polar region (up to 82.5°N) can cover nearly 100% of the Greenland ice sheet. Continuous ice tracking mode retracker can provide useful information about ice surfaces, that is, determining the snow coverage, ice sheet transaction margin, and the evolution of snow depth during winter more accurately. This study present the results obtained with SARAL satellite Altika radar altimeter over the Greenland ice sheet region. The altimeter high rate waveforms products are used for utilizing the full capability of the instrument. High resolution DEM (1 km) generated using ICESAT/GLAS altimeter has been used for selecting the good quality data over the study region. Four different retrackers—Ocean, ICE-1, ICE-2, and Sea-Ice—were tested on the SARAL altimeter data set and compared with the DEM extracted ice sheet elevations. Three different data analysis—region of interest (ROI), track analysis, and cross-over analysis—were performed for in-depth analysis of the ice height changes and back scattering coefficient variability. ROI's (1° × 0.5°) were selected based on accumulation dry snow zone, percolation zone, wet snow zone, and ablation zone. Finally to observe the effect of Ka band, SARAL results has been compared with the Envisat altimeter in terms of back scatter and error in the height retrieval due to penetration problem within the ice sheet layer. The new SARAL data set confirms the potential of ice altimetry and provides a new opportunity to monitor the ice sheet surface topography evolution.  相似文献   

On the aftershock sequence of a 4.6 mb earthquake of the Garhwal Himalaya     

Irene Sarkar  Ramesh Chander  Dalia Chatterjee 《Journal of Earth System Science》1995,104(4):683-691

Locally recorded data for eighteen aftershocks of a magnitude(m_b) 4.6 earthquake occurring near Ukhimath in the Garhwal Himalaya were analysed. A master event technique was adopted to locate seventeen individual aftershock hypocentres relative to the hypocentre of the eighteenth aftershock chosen as the master event. The aftershock epicentres define an approximately 30 km² rupture zone commensurate with the magnitude of the earthquake. The distribution of epicentres within this zone and the limited amount of first motion data support the view that a group of parallel, sub-vertical, sinistral strike-slip faults oriented N46°, transverse to the regional NW-SE trend of the Garhwal Himalaya, was involved in this seismic episode. Since the estimated focal depth range for aftershocks of this sequence is 3–14 km, we infer that this transverse fault zone extends through the upper crustal layer to a depth of 14 km at least.  相似文献   

Fine structure of seismotectonics in western Shillong massif,north east India     

S Mukhopadhyay  R Chander  K N Khattri 《Journal of Earth System Science》1993,102(2):383-398

The epicentral tract of the great Assam earthquake of 1897 of magnitude 8·7 was monitored for about 6 months using an array of portable seismographs. The observed seismicity pattern shows several diversely-oriented linear trends, some of which either encompass or parallel known geological faults. A vast majority of the recorded micro-earthquakes had estimated focal depths between 8–14 km. The maximum estimated depth was 45 km. On the basis of a seismic velocity model for the region reported recently and these depth estimates we suggest that the rupture zone of the great 1897 earthquake had a depth of 11–12 km under the western half of the Shillong massif. Four composite fault plane solutions define the nature of dislocation in three of the seismic zones. Three of them show oblique thrusting while one shows pure dip slip reverse faulting. The fault plane solutions fit into a regional pattern of a belt of earthquakes extending in NW-SE direction across the north eastern corner of the Bengal basin. The maximum principle stress axis is approximately NS for all the solutions in conformity with the inferred direction of the Indian-EuroAsian plate convergence in the eastern Himalaya.  相似文献   

Electrochemical reaction control of contact angles on copper and synthetic chalcocite in aqueous potassium diethyldithiophosphate solutions     

S. Chander  D.W. Fuerstenau 《International Journal of Mineral Processing》1975,2(4):333-352

The contact angles on synthetic chalcocite in potassium diethyldithiophosphate (KDTP) solutions have been compared with those on copper to delineate physico-chemical factors which might contribute to the flotation response of copper sulfides. The influence of a number of variables such as KDTP concentration, solution pH, gaseous environment and electrochemical pretreatment has been investigated. The results are discussed in terms of the thermodynamic and kinetic aspects of the system.  相似文献   

Landslide zoning in a part of the Garhwal Himalayas   总被引：21，自引：1，他引：20  

A. K. Pachauri  P. V. Gupta  R. Chander 《Environmental Geology》1998,36(3-4):325-334

 The Himalayas are undergoing constant rupturing in the thrust belt zone in the Garhwal Himalayas, due to which earthquake and mass movement activity is triggered. These processes of mass movement and landslides have been constantly modifying the landscape. Landslides are one of the indicators of the geomorphological modifications taking place in this active and fragile terrain. This work is aimed at providing another example of landslide susceptibility mapping based on geological and geomorphological attributes. The data collected from aerial photographs, topographic sheets and the image suggests that there is a correlation between the distribution of landslides and some of the geological and geomorphological factors, for example, the distance from an active fault, relative relief and slope. Parameters like factor of safety, altitude, relief, slope and the distance from the fault lineament have been included in the study. A rating system has been applied to the factors for arriving at a quantitative estimate of landslide susceptibility for each physiographic unit. Since terrain classification forms the foundation of this work, the entire study can be grouped into two sequential activities: (1) the terrain classification and (2) landslide susceptibility mapping. The result is the landslide susceptibility zoning map presented. The landslides have not been classified with respect to time and may represent the final result of the on-going geological, geomorphological and seismic activity since the Holocene period or late Pleistocene time when the glaciers retreated. The area chosen for the study lies between Badri gad and Barni gad in Yamuna valley region of the Garhwal Himalaya where a very large scale investment is in the pipe line for Hydroelectric power generation. Received: 12 August 1993 · Accepted: 13 January 1998  相似文献   

Estimation of hypocentral parameters of local earthquakes when crustal layers have constantP-velocities and dipping interfaces     

Irene Sarkar  R. Chander  K. N. Khattri  V. K. Gaur 《Journal of Earth System Science》1987,96(3):229-238

The paper describes an algorithm for estimating the hypocentral coordinates and origin time of local earthquakes when the wave speed model to be employed is a layered one with dipping interfaces. A constrained least-squared error problem has been solved using the penalty function approach, in conjunction with the sequential unconstrained optimization technique of Fiacco and McCormick. Joint confidence intervals for the computed parameters are estimated using the approach of Bard for nonlinear problems. These results show that when a hypocentre lies outside the array of recording stations and head waves from a dipping interface are involved, then its inclination must be taken into account for dip angles exceeding 5°.  相似文献