Analytical solution of advection–diffusion equation in heterogeneous infinite medium using Green’s function method     

ABHISHEK SANSKRITYAYN  NAVEEN KUMAR 《Journal of Earth System Science》2016,125(8):1713-1723

Some analytical solutions of one-dimensional advection–diffusion equation (ADE) with variable dispersion coefficient and velocity are obtained using Green’s function method (GFM). The variability attributes to the heterogeneity of hydro-geological media like river bed or aquifer in more general ways than that in the previous works. Dispersion coefficient is considered temporally dependent, while velocity is considered spatially and temporally dependent. The spatial dependence is considered to be linear and temporal dependence is considered to be of linear, exponential and asymptotic. The spatio-temporal dependence of velocity is considered in three ways. Results of previous works are also derived validating the results of the present work. To use GFM, a moving coordinate transformation is developed through which this ADE is reduced into a form, whose analytical solution is already known. Analytical solutions are obtained for the pollutant’s mass dispersion from an instantaneous point source as well as from a continuous point source in a heterogeneous medium. The effect of such dependence on the mass transport is explained through the illustrations of the analytical solutions.  相似文献   

Relict magnesian calcite oolite and subsidence of the Amazon shelf     

NARESH KUMAR  JOHN E. DAMUTH  MARCUS A. GORINI 《Sedimentology》1977,24(1):143-148

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Tectonochemistry and p-t Conditions of Ramgarh and Almora Gneisses from Askot Klippe,Kumaun Lesser Himalaya     

Biraja P. DAS  Mallickarjun JOSHI  Ashutosh KUMAR 《《地质学报》英文版》2019,93(2):322-343

The chemical and petrological correlation of metamorphic nappes and klippes overlying the Proterozoic sedimentary units in the Kumaun Himalaya is still debated. The Ramgarh and Almora gneisses, not previously distinguished in the Askot Klippe, show distinct field, petrological and chemical signatures markedly similar to the tectonostratigraphic disposition of the Almora Nappe. A negative Eu anomaly in the Ramgarh granitic gneisses indicates lesser plagioclase fractionation while the Eu anomaly in the Almora pelitic gneisses is likely to have been controlled by feldspar crystallization in restites. During the anatexis at 776°C temperature and 6.6 kbar pressure, the melt moved slightly away to its crystallization sites. The Rb/Sr ratio ?0.54 and Nb ?10 ppm is consistent with the granodioritic composition. The negative Sr anomaly in the underlying Ramgarh granitic gneisses indicates a distinct mantle derived source/plagioclase fractionation with a notable correspondence to other late orogenic granites, particularly the basement Ulleri gneisses from the Nepal Himalaya. Ramgarh gneisses plot in the late-and post-COLG field. The Askot ensemble is likely to be the tectonometamorphically reworked basement, viz. the Ramgarh Group along with its metapelitic cover o f the Almora Group, together comprising southward thrust remnants of the leading edge of the Indian Plate that collided with Tibet during the Tertiary Himalayan orogeny.  相似文献   

Near shore waves,long-shore currents and sediment transport along micro-tidal beaches,central west coast of India     

Sajiv Philip CHEMPALAYIL  V Sanil KUMAR  G Udhaba DORA  Glejin JOHNSON 《国际泥沙研究》2014,29(3):402-413

Coastlines are undergoing constant geomorphologic changes with respect to the incident wave climate.Based on waves measured at 9 m water depth,simulation of near shore wave transformation is done using REFDIF-1numerical model and the near shore breaker parameters are estimated at two micro-tidal beaches along central west coast of India.Model results are validated with measured values.From the breaker parameters,long-shore current and long-shore sediment transport rates（LSTR） are computed by using semi-empirical equations.Estimated long-shore current and LSTR are showing dramatic variations with respect to seasons.Predominant direction of LSTR is observed towards north since the approach waves are from south-west direction during pre-monsoon and post monsoon.During monsoon season,waves are from west south-west and resulted in southerly transport.The estimated annual net and gross LSTR by Cambridge Environmental Research Consultants（CERC） at two locations are in the same order whereas LSTR estimated by Walton ＆ Bruno and Kamphuis equations are showing different estimations because of difference in surf-zone width and foreshore slope between the two locations.For micro-tidal beaches with length less than 6 km,Kamphuis equation is giving agreeable estimation of LSTR.Sensitivity analysis of LSTR estimate shows that coastal inclination is the prominent factor in determining LSTR than incident wave angle.  相似文献   

The future of mountain agriculture amidst continual farm-exit,livelihood diversification and outmigration in the Central Himalayan villages     

Niyati NAUDIYAL  Kusum ARUNACHALAM  Ujjwal KUMAR 《山地科学学报》2019,(4)

Agrarian patterns in mountain ecosystems have seen a considerable change in the past decades with a vast proportion of the population abandoning traditional agriculture and diversifying their livelihood options, primarily through out-migration. This trend is especially common amongst the subsistence based family-farming communities in developing countries. This study aims at assessing methods of livelihood diversification and factors influencing farm-exit in Central Himalayan villages of Uttarakhand, India, while trying to understand local perspectives on challenges in pursuing agriculture as a viable livelihood option. We collected qualitative and quantitative data from 951 households across 60 villages evenly distributed across six hill districts of Uttarakhand, using key-person interviews and household surveys. The results of the study highlight that farm-exit is significantly influenced by livelihood diversification, number of migrants, number of female family members, and availability of irrigation facilities. In general, perception of the respondents towards agriculture as a viable livelihood option is rather unenthusiastic, with 87% of the respondents citing human wildlife conflict as the main challenge in pursuing farming, amongst several other challenges. Diversification is an integral component of present rural economy with 80.13% of the total population dependent on more than one source of income, to maintain their livelihoods. However, there is no statistically significant influence of livelihood diversification on annual income of the household. If agro-based entrepreneurial ventures are to be promoted in the region there is an urgent need for timely introduction of radical policy, institutional, and land-reforms. Economic uplifting of the local population through such efforts can also be a possible solution to the growing trends of out-migration in the state.  相似文献   

SLURP model and GIS for estimation of runoff in a part of Satluj catchment,India     

SANJAY K. JAIN  NARESH KUMAR  TANVEAR AHMAD  G. W. KITE 《水文科学杂志》2013,58(6):875-884

Abstract

The snow and rain in the Himalayas are the main sources of supply for the rivers in the Indo-Gangetic plains. Irrigation, hydropower generation, and water supply are very much dependent on the availability of water in the Himalaya rivers. Mathematical models serve as important aids for the estimation of water availability in rivers. In the present study the SLURP watershed model is applied to a rainfed area of the Satluj catchment located in the western Himalayas, India. The SLURP model developed at NHRI, Canada, is a distributed conceptual model which simulates the behaviour of a watershed by carrying out vertical water balances for each element of a matrix of landcovers and subareas of a watershed and then routing the resulting runoff between subareas. The ILWIS geographic information system was used to prepare the input data required for SLURP and land use data were obtained from the IRS satellite LISS II visible and near infrared sensors. The simulated flows at the Bhakhra Dam outlet of the Satluj catchment were computed and found to compare well with the observed flows.  相似文献   

Doppler SODAR observations of the temperature structure parameter during monsoon season over a tropical rural station,Gadanki     

M SHRAVAN KUMAR  V K ANANDAN  AMIT KESARKAR  P NARASIMHA REDDY 《Journal of Earth System Science》2011,120(1):65-72

Doppler SODAR (Sound Detection and Ranging) measurements over a tropical Indian station at National Atmospheric Research Laboratory (NARL), Gadanki (13.5°N, 79.2°E) during two consecutive monsoon seasons, 2007 and 2008, are investigated to study the influence of mechanically generated turbulence on temperature structure parameter (C_T²)_{\rm T}^{2}) in the convective boundary layer. Increase in the C_T²_{\rm T}^{2} is observed after the arrival of monsoon for both seasons. Contribution of vertical wind shear in horizontal wind component to C_T²_{\rm T}^{2} due to zonal winds is responsible for the increase observed in the temperature structure parameter which is inferred from the results obtained. C_T²_{\rm T}^{2} is found to be increased by an order of 2 in both the lower and upper altitudes, respectively. Magnitude of wind speed is reported to be doubled with the arrival of monsoon. It is also observed that, southwest monsoon wind modulates the day-to-day variations of wind pattern over this station during the onset phase of monsoon season. The lower variability observed at lower height is attributed to the complex topography surrounding this region.  相似文献   

Impact of additional surface observation network on short range weather forecast during summer monsoon 2008 over Indian subcontinent   总被引：1，自引：0，他引：1  

PRASHANT KUMAR  RANDHIR SINGH  P C JOSHI  P K PAL 《Journal of Earth System Science》2011,120(1):53-64

The three dimensional variational data assimilation scheme (3D-Var) is employed in the recently developed Weather Research and Forecasting (WRF) model. Assimilation experiments have been conducted to assess the impact of Indian Space Research Organisation’s (ISRO) Automatic Weather Stations (AWS) surface observations (temperature and moisture) on the short range forecast over the Indian region. In this study, two experiments, CNT (without AWS observations) and EXP (with AWS observations) were made for 24-h forecast starting daily at 0000 UTC during July 2008. The impact of assimilation of AWS surface observations were assessed in comparison to the CNT experiment. The spatial distribution of the improvement parameter for temperature, relative humidity and wind speed from one month assimilation experiments demonstrated that for 24-h forecast, AWS observations provide valuable information. Assimilation of AWS observed temperature and relative humidity improved the analysis as well as 24-h forecast. The rainfall prediction has been improved due to the assimilation of AWS data, with the largest improvement seen over the Western Ghat and eastern India.  相似文献   

Development of regional wheat VI-LAI models using Resourcesat-1 AWiFS data     

SASMITA CHAURASIA  R NIGAM  B K BHATTACHARYA  V N SRIDHAR  K MALLICK  S P VYAS  N K PATEL  J MUKHERJEE  CHANDER SHEKHAR  DHIRAJ KUMAR  K R P SINGH  G D BAIRAGI  N L PUROHIT  J S PARIHAR 《Journal of Earth System Science》2011,120(6):1113-1125

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Simulations of Eurasian Winter Temperature Trends in Coupled and Uncoupled CFSv2     

Thomas W.COLLOW  Wanqiu WANG  Arun KUMAR 《大气科学进展》2018,35(1):14-26

Conflicting results have been presented regarding the link between Arctic sea-ice loss and midlatitude cooling, particularly over Eurasia. This study analyzes uncoupled(atmosphere-only) and coupled(ocean–atmosphere) simulations by the Climate Forecast System, version 2(CFSv2), to examine this linkage during the Northern Hemisphere winter, focusing on the simulation of the observed surface cooling trend over Eurasia during the last three decades. The uncoupled simulations are Atmospheric Model Intercomparison Project(AMIP) runs forced with mean seasonal cycles of sea surface temperature(SST)and sea ice, using combinations of SST and sea ice from different time periods to assess the role that each plays individually,and to assess the role of atmospheric internal variability. Coupled runs are used to further investigate the role of internal variability via the analysis of initialized predictions and the evolution of the forecast with lead time.The AMIP simulations show a mean warming response over Eurasia due to SST changes, but little response to changes in sea ice. Individual runs simulate cooler periods over Eurasia, and this is shown to be concurrent with a stronger Siberian high and warming over Greenland. No substantial differences in the variability of Eurasian surface temperatures are found between the different model configurations. In the coupled runs, the region of significant warming over Eurasia is small at short leads, but increases at longer leads. It is concluded that, although the models have some capability in highlighting the temperature variability over Eurasia, the observed cooling may still be a consequence of internal variability.  相似文献