Lithospheric structure beneath Laxmi Ridge and late Cretaceous geodynamic events     

O. P. Pandey  P. K. Agrawal  J. G. Negi 《Geo-Marine Letters》1995,15(2):85-91

The geophysically unusual Laxmi Ridge (eastern basin, Arabian Sea) is associated with a prominent elongated negative gravity anomaly. A seismically and geodynamically constrained detailed 2D gravity modeling suggests an 11-km-thick normal oceanic crust and an asthenospheric upwarp to a depth of 35 km. We attribute the apparent thickening of the crust to a possible emplacement of an anomalous subcrustal low-density layer between 11 and 19 km depth. We hypothesize that a K-T boundary bolide impact near the Bombay offshore led to several geological events, including eruption of Deccan flood basalts. The spreading Carlsberg Ridge in the Indian Ocean and rifting associated with Deccan volcanism generated the compressive regime, which perhaps originated the Laxmi Ridge.  相似文献   

New Runge-Kutta algorithms for numerical simulation in dynamical astronomy     

J. R. Dormand  P. J. Prince 《Celestial Mechanics and Dynamical Astronomy》1978,18(3):223-232

Some new Runge-Kutta and Runge-Kutta-Nystrom algorithms are presented for the solution of ordinary differential equations of the initial value type. The methods are compared with others in integrating the equations of motion of the two body problem and are shown to offer advantages in efficiency. It is also demonstrated that the new methods can be tuned to achieve some measure of global error control.  相似文献   

Topographic correction of ALOS-PALSAR images using InSAR-derived DEM     

Anup Das  Ritesh Agrawal  Shiv Mohan 《国际地球制图》2015,30(2):145-153

Topographic corrections of synthetic aperture radar (SAR) images over hilly regions are vital for retrieval of correct backscatter values associated with natural targets. The coarse resolution external digital elevation models (DEM) available for topographic corrections of high resolution SAR images often result into degradation of spatial resolution or improper estimation of backscatter values in SAR images. Also, many a times the external DEMs do not spatially co-register well with the SAR data. The present study showcases the methodology and results of topographic correction of ALOS-PALSAR image using high resolution DEM generated from the same data. High resolution DEMs of Jaipur region, India were generated using multiple pair SAR images acquired from ALOS-PALSAR using interferometric (InSAR) techniques. The DEMs were validated using differential global positioning system measured elevation values as ground control points and were compared with photogrammetric DEM (advanced spaceborne thermal emission and reflection radiometer – ASTER) and SRTM (Shuttle Radar Topography Mission) DEM. It was observed that ALOS-PALSAR images with optimum baseline parameters produced high resolution DEM with better height accuracy. Finally, the validated DEM was used for topographic correction of ALOS-PALSAR images of the same region and were found to produce better result as compared with ASTER and SRTM-DEM.  相似文献   

Mass Balance Reconstruction Since 1963 and Mass Balance Model for East Rathong Glacier,Eastern Himalaya,Using Remote Sensing Methods          下载免费PDF全文

Anubha Agrawal  Shresth Tayal 《Geografiska Annaler: Series A, Physical Geography》2015,97(4):695-707

In this study mass balance, accumulation, ablation, runoff and temperature lapse rate for the East Rathong glacier are estimated for the time period 1963–2011 using remote sensing methods and climate data. A mass balance model is proposed for the glacier that computes mass balance as difference of volumes of consecutive years. Volume estimates of glacier are based on application of volume–area scaling law to glacier area computed from satellite images. It is observed that the glacier is summer‐accumulation type. Time series analysis is applied to the annual mass balance series. The annual mass balance of the glacier is showing a statistically significant negative trend. It is also showing a statistically significant shift in the year 1985. Change in the mean of mass balance before and after the shift year is 0.19 m w.e. Cumulative mass balance suggests that the glacier has lost ～11 m w.e. or 0.047 km³ during the last 48 years.  相似文献   

Environmentally sustainable use of sandstone slurry in self-compacting concrete     

Basu  Prarthita  Gupta  Ramesh Chandra  Agrawal  Vinay 《Natural Hazards》2021,109(3):2399-2421

Natural Hazards - Dried sandstone slurry (DSS) is generated during mining and processing of stone and is accounted as man-made hazardous waste material, contaminating the environment in nearby...  相似文献   

Mapping land degradation by comparison of vegetation production to spatially derived estimates of potential production   总被引：4，自引：0，他引：4  

K.J. Wessels  S.D. Prince  I. Reshef 《Journal of Arid Environments》2008,72(10):1940-1949

There is an urgent need for quantitative methods by which actual, as opposed to potential degradation can be mapped using spatially consistent criteria for large regions. This study tested the Local NPP Scaling (LNS) method, where the growth season sum NDVI (∑NDVI), a surrogate for productivity, of each pixel was expressed relative to the highest values (90th percentile) of ∑NDVI observed in all pixels falling within the same land capability unit (LCU). The objective of this study was to determine if the LNS approach can be used to map degraded areas: (i) by determining if areas with low LNS values co-occur with degraded areas mapped with Landsat TM and (ii) testing the persistence of these areas over multiple years. Most of the areas with low LNS values did coincide with degraded areas, with the exception of four LCUs, which either contained steep precipitation gradients or landscape variability, which probably obscured the human impacts. The performance of the LNS method is therefore largely determined by the level of detail of the stratification data (e.g. LCUs) used. The conclusion is that the LNS method is a valuable tool for mapping land degradation at a regional scale.  相似文献   

Effect of simultaneous state–parameter estimation and forcing uncertainties on root-zone soil moisture for dynamic vegetation using EnKF     

Alejandro Monsivais-Huertero  Wendy D. Graham  Jasmeet Judge  Divya Agrawal 《Advances in water resources》2010

In this study, an EnKF-based assimilation algorithm was implemented to estimate root-zone soil moisture (RZSM) using the coupled LSP–DSSAT model during a growing season of corn. Experiments using both synthetic and field observations were conducted to understand effects of simultaneous state–parameter estimation, spatial and temporal update frequency, and forcing uncertainties on RZSM estimates. Estimating the state–parameters simultaneously with every 3-day assimilation of volumetric soil moisture (VSM) observations at 5 depths lowered the average standard deviation (ASD) and the root mean square error (RMSE) for RZSM by approximately 1.77% VSM (78%) and 2.18% VSM (93%), respectively, compared to the open-loop ASD where as estimating only states lowered the ASD by approximately 1.26% VSM (56%) and the RMSE by 1.66% VSM (71%). The synthetic case obtained RZSM estimates closer to the observations than the MicroWEX-2 case, particularly after precipitation/irrigation events. The differences in EnKF performance between MicroWEX-2 and synthetic observations may indicate other sources of errors in addition to those in parameters and forcings, such as errors in model biophysics.  相似文献   

Pn wave velocity and Moho geometry in north eastern India     

S. S. Rai  K. S. Prakasam  N. Agrawal 《Journal of Earth System Science》1999,108(4):297-304

Pn velocity has been computed across the NE India and Moho geometry constrained, using regional earthquake travel times recorded by a network of 30 seismological stations operated during February-May 1993. Using an appropriate velocity model and the arrival times at the network stations, preliminary hypocentres of 16 regional earthquakes provided by NEIC were also improved. The average Pn wave velocity in NE India has been found to be 8.5 ±0.2 km/s. It varies from 8.3 to 8.5 km/s beneath the Shillong Plateau, Mikhir hills and Assam valley, which is significantly higher than those in other parts of India. The crustal thickness in NE India is also high, varying from 45–49 km under the Shillong plateau and the adjoining region to 55–65 km in the convergence zone. The presence of a thick crust and high Pn velocity suggests that the lithosphere in NE India is colder, as also indicated by the observed deeper level (45-51 km) seismicity of the region.  相似文献   

Ecological risk assessment of trace metal accumulation in sediments of Veraval Harbor,Gujarat, Arabian Sea   总被引：1，自引：0，他引：1  

S. Sundararajan  Mukunda Kesari Khadanga  J. Prince Prakash Jeba Kumar  S. Raghumaran  R. Vijaya  Basanta Kumar Jena 《Marine pollution bulletin》2017,114(1):592-601

In this study, different types of indices were used to assess the ecological risk of trace metal contamination in sediments on the basis of sediment quality guidelines at Veraval Fishery Harbor. Sediment samples were collected from three sectors in pre-, post-, and monsoon seasons in 2006. Trace metal concentrations were higher in the inner sector during post-monsoon, and it showed the highest statistical significance (p < 0.01) among the stations. Pollution load index was higher than unity, indicating alternation by effluent discharge from industries. Enrichment factor and geo-accumulation index showed that Cd, Pb, and Zn were enriched in the northern part of the harbor and Pb had accumulated in the harbor sediment. The ecological risk assessment index revealed that Ni, Zn, and Pb were higher than the effect range median values, indicating their potential toxicity to the aquatic environment in the Veraval Harbor. Hence, the harbor is dominated by anthropogenic activities rather than natural process.  相似文献   

Multifaceted Role of Microalgae for Municipal Wastewater Treatment: A Futuristic Outlook toward Wastewater Management     

Rahul Kumar Goswami  Komal Agrawal  Pradeep Verma 《洁净——土壤、空气、水》2023,51(3):2100286

Municipal wastewater (MWW) or urban wastewater (UWW) is generated by the domestic consumption of freshwater, which contains a huge amount of nutrients. The release of unprocessed wastewater causes eutrophication and harms aquatic life. Moreover, ingestion of polluted MWW causes a severe negative impact on human health. Microalgae are unicellular, eukaryotic photosynthetic organisms and have the capability of nutrient assimilation in the presence of light. Moreover, the produced biomass can be used for the generation of value-added bioproducts such as bioenergy. However, conventional microalgae-based MWW treatment is not as sustainable on a commercial scale. Therefore, more advanced approaches using microalgae need to be integrated in wastewater cultivation systems to improve nutrient removal efficiency. Thus, the present review explores the use of microalgae for the removal of nutrients from MWW, provides an outlook of direct and indirect methods of nutrient uptake from wastewater and the effects of the influencing factors in biomass growth. Moreover, the review also gives insight into recent approaches used for MWW treatment and the applications of algal biomass resulting from treated wastewater. It is predicted that microalgae-based MWW treatment systems will be a significant green approach to help eliminate nutrient loads and implement circular economy.  相似文献