Switch in chemical weathering caused by the mass balance variability in a Himalayan glacierized basin: a case of Chhota Shigri Glacier     

Naveen Kumar  Martyn Tranter  Parmanand Sharma  Manish Pandey  Prabhat Ranjan 《水文科学杂志》2019,64(2):179-189

Long-term data (2003–2015) on meltwater chemistry, mass balance and discharge of a benchmark glacier (Chhota Shigri Glacier, India) were studied to determine any association between these variables. To infer the factors governing the alteration of chemical weathering processes in glacierized basins, multi-annual records of the hydrochemical indices (Ca²⁺+Mg²⁺/Na⁺+K⁺) and the C-ratio were also examined. A succession of negative mass balance years has resulted in a decline in solute concentrations in the runoff, as discharge has increased. The (Ca²⁺+Mg²⁺/Na⁺+K⁺) and C-ratio are highest during periods of negative annual mass balance, when the spatial extent of the channelized drainage system increases. Conversely, these ratios are lowest in positive mass balance years, when the spatial extent of the channelized drainage system decreases, and chemical weathering in the distributed drainage system becomes more dominant. This paper is the first to show the inter-annual linkages between meltwater chemistry, mass balance and discharge for a valley glacier.  相似文献   

First Observations from the Multi-Application Solar Telescope (MAST) Narrow-Band Imager     

Shibu K. Mathew  Ankala Raja Bayanna  Alok Ranjan Tiwary  Ramya Bireddy  Parameswaran Venkatakrishnan 《Solar physics》2017,292(8):106

The Multi-Application Solar Telescope is a 50 cm off-axis Gregorian telescope recently installed at the Udaipur Solar Observatory, India. In order to obtain near-simultaneous observations at photospheric and chromospheric heights, an imager optimized for two or more wavelengths is being integrated with the telescope. Two voltage-tuneable lithium-niobate Fabry–Perot etalons along with a set of interference blocking filters have been used for developing the imager. Both of the etalons are used in tandem for photospheric observations in Fe i 6173 Å and chromospheric observation in H\(\alpha\) 6563 Å spectral lines, whereas only one of the etalons is used for the chromospheric Ca II line at 8542 Å. The imager is also being used for spectropolarimetric observations. We discuss the characterization of the etalons at the above wavelengths, detail the integration of the imager with the telescope, and present a few sets of observations taken with the imager set-up.  相似文献   

Scanning sky monitor (SSM) onboard AstroSat     

M. C. Ramadevi  S. Seetha  Dipankar Bhattacharya  B. T. Ravishankar  N. Sitaramamurthy  G. Meena  M. Ramakrishna Sharma  Ravi Kulkarni  V. Chandra Babu  Kumar  Brajpal Singh  Anand Jain  Reena Yadav  S. Vaishali  B. N. Ashoka  Anil Agarwal  K. Balaji  G. Nagesh  Manoj Kumar  Dhruti Ranjan Gaan  Prashanth Kulshresta  Pankaj Agarwal  Mathew Sebastian  A. Rajarajan  D. Radhika  Anuj Nandi  V. Girish  Vivek Kumar Agarwal  Ankur Kushwaha  Nirmal Kumar Iyer 《Experimental Astronomy》2017,44(1):11-23

Scanning Sky Monitor (SSM) onboard AstroSat is an Xray sky monitor in the soft X-ray band designed with a large field of view to detect and locate transient X-ray sources and alert the astronomical community about interesting phenomena in the X-ray sky. SSM comprises position sensitive proportional counters with 1D coded mask for imaging. There are three detector units mounted on a platform capable of rotation which helps covering about 50% of the sky in one full rotation. This paper discusses the elaborate details of the instrument and few immediate results from the instrument after launch.  相似文献   

A multi-layered backpropagation artificial neural network algorithm for UV spectral classification     

Soma Mukherjee  Ujjwal Bhattacharya  S. K. Parui  Ranjan Gupta  Ravi K. Gulati 《Astrophysics and Space Science》1996,239(2):361-373

In this paper we present an application of an artificial neural network model based on a multi-layered backpropagation algorithm for spectral classification of UV data from the International Ultraviolet Explorer (IUE) low dispersion spectra reference atlas. The model used is similar to that of von Hippel et al. (1994), and is found to reduce the classification error as compared to the recently reported results on the same data set (Gulati et al. 1994b). The improved version of the network is much simpler in structure and the training time is reduced by a factor of almost 20. Such networks will prove very useful in efficient classification of large databases Subject headings: neural networks, stellar spectra, classification  相似文献   

Estimating snow distribution over a large area and its application for water resources     

So Kazama  Hirokazu Izumi  Priyantha Ranjan Sarukkalige  Takayuki Nasu  Masaki Sawamoto 《水文研究》2008,22(13):2315-2324

The spatial and temporal distribution of the snow water equivalent (SWE), snow density and snow depth were estimated by a method combining remote sensing technology and degree‐day techniques over a study area of 370 000 km². The advantages of this simulation model are its simplicity and the availability of degree‐day parameters, which can be successively evaluated by referring to snow area maps created from satellite images. This simulation worked very well for estimating SWE and helped to separate the areas of thin snow cover from heavier snowfall. However, shallow snow in warm regions led to some misjudgments in the snow area maps because of the time lag between when the satellite image was acquired and the simulation itself. Vulnerable areas, where a large variation in the amount of snow affects people's life, could be identified from the differences between heavy and light snow years. This vulnerability stems from a predicted lack of irrigation water for rice production caused by future climate change. The model developed in this study has the potential to contribute to water management activities and decision‐making processes when considering necessary adaptations to future climate change. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Temporal variations in Sr and 87Sr/86Sr of the Ganga headwaters: estimates of dissolved Sr flux to the mainstream     

Gyana Ranjan Tripathy  Vineet Goswami  Sunil Kumar Singh  G. J. Chakrapani 《水文研究》2010,24(9):1159-1171

The headwaters of the Ganga (the Alaknanda, Bhagirathi and the Ganga) were analysed for their dissolved major ions, Sr and ⁸⁷Sr/⁸⁶Sr on a biweekly to monthly basis over a period of one year to determine their temporal variations and the factors contributing to them. The concentrations of major ions and Sr show significant seasonal variation with lower values during monsoon period in all the three rivers. A similar trend is also observed for ⁸⁷Sr/⁸⁶Sr and Na*/Ca (Na* = Na_r? Cl_r) suggesting relatively lower contribution of Sr and Na from silicates (which are more radiogenic in Sr) during monsoon. Budget calculations show that silicate derived dissolved Sr (Sr_s) in the river Ganga, Alaknanda and the Bhagirathi varied from 10 ± 4 to 27 ± 11, 7 ± 3 to 30 ± 12, 16 ± 6 to 57 ± 23% of measured Sr respectively with lower values during monsoon. The relative decrease in silicate erosion compared to carbonate during monsoon can result from several factors, these include higher dissolution kinetics of the carbonates, lower water–rock interaction time and availability of larger area for weathering. The annual discharge weighted Sr flux derived from the time series data is higher by ～20% from that based on peak flow Sr, and lower by ～40% compared to that derived from lean flow Sr concentration. The area‐normalized annual flux of dissolved Sr from the Ganga at Rishikesh is about five times its flux at Rajshahi (Bangladesh) and a few other major global rivers, such as the Amazon, indicating higher erosion rate over the Himalaya. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Tracer-based estimation of temporal variation of water sources: an insight from supra- and subglacial environments     

Naveen Kumar  Tirumalesh Keesari  S. Chidambaram  Shyam Ranjan  Mohd Soheb 《水文科学杂志》2013,58(11):1717-1732

ABSTRACT

The temporal variations in electrical conductivity and the stable isotopes of water, δD and δ¹⁸O, were examined at Chhota Shigri Glacier, India, to understand water sources and flow paths to discharge. Discharge is highly influenced by supraglacially derived meltwater during peak ablation, and subglacial meltwaters are more prominent at the end of the melt season. The slope of the best fit linear regression line for δD versus δ¹⁸O, for both supraglacial and runoff water, is lower than that for precipitation (snow and rain) and surface ice, indicating strong isotopic fractionation associated with the melting processes. The slope of the local meteoric water line (LMWL) is close to that of the global meteoric water line (GMWL), reflecting that the moisture source is predominantly oceanic. The d-excess variation in rainwater confirms that the southwest monsoon is the main contributor during summer while the remainder including winter is mostly influenced by westerlies.  相似文献   

Economic impacts of Pink Hibiscus Mealybug in Florida and the United States     

Ram Ranjan 《Stochastic Environmental Research and Risk Assessment (SERRA)》2006,20(5):353-362

This paper estimates the expected annual impacts of the Pink Hibiscus Mealybug infestation on the economies of Florida and the rest of the United States. The approach involves a Markov chain analysis wherein both short run and long run expected damages from infestation are calculated. Use is made of the CLIMEX model that predicts the potential pest-establishment regions in the US. While predictions based upon the CLIMEX model extend the scope of damages beyond Florida, the damages are significantly dependent upon the rate of arrival and detection of species in those regions. Damages are significantly higher when a longer time horizon is considered. When nursery owners bear the full cost of quarantines in the form of loss of sales and treatment costs of infected plants, the cost-effectiveness of quarantines as a regulatory tool is diminished. The long run propensity of the system, in terms of the fraction of time spent in the possible ‘states’ of infestation and control, determines the extent of damages, and not the annual value of crops that could be potential hosts to the pest.

Ram RanjanEmail: Phone: +1-352-3921881Fax: +1-352-3929898

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Riparian influence on hyporheic‐zone formation downstream of a small dam in the Blackland Prairie region of Texas     

Jacquelyn R. Duke  Joseph D. White  Peter M. Allen  Ranjan S. Muttiah 《水文研究》2007,21(2):141-150

Small‐order streams have highly variable flows that can result in large temporal and spatial variation of the hyporheic zone. Dam construction along these intermittent headwater streams alters downstream flow and influences the hydrologic balance between stream water and the adjacent riparian zone. A 3‐year site study was conducted along an impounded second‐order stream to determine the water balance between stream, unsaturated zone, groundwater and riparian vegetation. The presence of the upstream impoundment provided near‐perennial water flow in the stream channel. The observed woody plant transpiration accounted for 71% of average annual water loss in the site. The overall contribution of stream water via the hyporheic zone to site water balance was 73 cm, or 44% of total inputs. This exceeded both rainfall and upland subsurface contribution to the site. A highly dynamic hyporheic zone was indicated by high water use from woody plants that fluctuated seasonally with stream water levels. We found leaf area development in the canopy layer to be closely coupled with stream and groundwater fluctuations, indicating its usefulness as a potential indicator of site water balance for small dam systems. The net result of upstream impoundment increased riparian vegetation productivity by influencing movement of stream water to storage in the groundwater system. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Composite interstellar grains   总被引：2，自引：0，他引：2  

D. B. Vaidya  Ranjan Gupta  T. P. Snow 《Monthly notices of the Royal Astronomical Society》2007,379(2):791-800

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