Hysteresis‐based analysis of overland metal transport     

Surendra Kumar Mishra  J. J. Sansalone  Vijay P. Singh 《水文研究》2003,17(8):1579-1606

Introducing a concept of equivalent mass depth of flow, this study describes the phenomenon of non‐point source pollutant (metal) transport for pavement (or overland) flow in analogy with wave propagation in wide open channels. Hysteretic and normal mass rating curves are developed for runoff rate and mass of 12 dissolved and particulate‐bound metal elements (pollutants) using the rainfall‐runoff and water quality data of the 15 × 20 m² instrumented pavement in Cincinnati, USA. Normal mass rating curves developed for easy computation of pollutant load are found to be of a form similar to Manning's, which is valid for open channel flows. Based on the hysteresis analysis, wave types for dissolution and mixing of particulate‐bound metals are identified. The analysis finds that the second‐order partial‐differential equation normally used for metal transport does not have the efficacy to describe fully the strong non‐linear phenomena such as is described for various metal elements by dynamic waves. In addition, the proportionality concept of the popular SCS‐CN concept is extended for determining the potential maximum metal mass M_p of all the 12 elements transported by a rain storm and related to the antecedent dry period (ADP). For the primary metal zinc element, M_p is found to increase with the ADP and vice versa. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

Impact of Satellite Altimetry on Simulations of Sea Level Variability by an Indian Ocean Model     

S. K. Singh  Sujit Basu  Raj Kumar  Vijay K. Agarwal 《Marine Geodesy》2001,24(1):53-63

This article describes the impact of satellite altimeter data on the simulations of sea level variability (SLV) by a nonlinear reduced gravity model of the entire Indian Ocean. The model has been forced by 6-hourly analyzed wind stress data containing SSM/I observations and has been able to produce realistic circulation features. However, SLV values observed by Topex/Poseidon altimeter do not fit these simulations because of imperfect initial data. Hence an attempt has been made to initialize the model using altimeter data. The initialized model-generated SLVvalues have been compared with SLV derived by altimeter for monsoon as well as nonmonsoon months of 1996. Experimental runs have been performed for 10 days, 20 days, and one month. It has been found that the initialized model results on the final day of these experiments are in very good agreement with altimeter data of the same day. It is thus possible, in principle, to hindcast and forecast sea level variations in the time scale of 10 days to one month with the availability of good quality wind data for forcing the model and altimeter observations of sea level for initializing it.  相似文献   

Estimating Deep Seafloor Interface and Volume Roughness Parameters Using the Multibeam-Hydrosweep System     

Bishwajit Chakraborty  Hans Werner Schenke  Vijay Kodagali  Rick Hagen 《Marine Geodesy》2002,25(1):19-26

Utilizing a hull-mounted, multinarrow beam echosounder onboard RV Polarstern, we measured variation of acoustic backscatter with incidence angles at two different sites in the Southern Oceans (Agulhas Plateau and the Riiser Larsen Sea). We modeled the data, using a composite roughness model, including water-sediment interface roughness and sediment volume roughness parameters. The model effectively uses the near normal incidence angle backscatter to determine the seafloor interface roughness parameters employing Helmholtz-Kirchhoff theory. Beyond 20° incidence angles, an application of Rayleigh-Rice theory is made by using a necessary splicing technique (combining both of the theories at 20° incidence angle). The estimated interface and volume roughness parameters are found to be in accordance with the known area geology.  相似文献   

Recent changes in the winter distribution and movements of northern Atlantic cod (Gadus morhua Linnaeus, 1758) on the Newfoundland-Labrador Shelf     

Kulka  David W.; Wroblewski  J. S.; Narayanan  Savi 《ICES Journal of Marine Science》1995,52(6):889-902

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Bioaccumulation of heavy metals in organs of fresh water fish Cyprinus carpio (Common carp)   总被引：3，自引：2，他引：1  

R. Vinodhini M.Sc.  M.Phil.  M. Narayanan M.Sc.  Ph.D. 《International Journal of Environmental Science and Technology》2008,5(2):179-182

The objective of the present study is to determine the bioaccumulation of heavy metals in various organs of the fresh water fish exposed to heavy metal contaminated water system. The experimental fish was exposed to Cr, Ni, Cd and Pb at sublethal concentrations for periods of 32 days. The elements Cd, Pb, Ni and Cr were assayed using Shimadzu AA 6200 atomic absorption spectrophotometery and the results were given as μ/g dry wt. The accumulation of heavy metal gradually increases in liver during the heavy metal exposure period. All the results were statistically significant at p < 0.001. The order of heavy metal accumulation in the gills and liver was Cd > Pb > Ni > Cr and Pb > Cd > Ni > Cr. Similarly, in case of kidney and flesh tissues, the order was Pb > Cd > Cr > Ni and Pb > Cr > Cd > Ni. In all heavy metals, the bioaccumulation of lead and cadmium proportion was significantly increased in the tissues of Cyprinus carpio (Common carp).  相似文献   

Variability of surface roughness and turbulence intensities at a coastal site in India   总被引：4，自引：0，他引：4  

Radhika Ramachandran  J. Winston Jeeva Prakash  K. Sen Gupta  K. Narayanan Nair  P. K. Kunhikrishnan 《Boundary-Layer Meteorology》1994,70(4):385-400

Surface-layer features with different prevailing wind directions for two distinct seasons (Southwest Monsoon and Northeast Monsoon) on the west coast of India are studied using data obtained from tower-based sensors at a site located about 500 m from the coast. Only daytime runs have been used for the present analysis. The surface boundary-layer fluxes have been estimated using the eddy correlation method. The surface roughnessz ₀ obtained using the stability-corrected wind profiles (Paulson, 1970) has been found to be low for the Southwest monsson season. For the other season,z ₀ is relatively high. The drag coefficientC _D varies with height in the NE monsoon season but not in the season with lowz ₀. This aspect is reflected in the wind profiles for the two seasons and is discussed in detail. The scaling behaviour of friction velocityu _* and the turbulence intensity of longitudinal, lateral and vertical winds _u, _v and _w, respectively) are further examined to study their dependence on fetch. Our study shows that for the non-dimensional case, _u/u_* and _v/u_* do not show any surface roughness dependence in either season. On the other hand, for _w/u_* for the season with lowz ₀, the values are seen to agree well with that of Panofskyet al. (1977) for homogeneous terrain whereas for the other season with highz ₀, the results seem to conform more to the values observed by Smedman and Högström (1983) for coastal terrain. The results are discussed in the light of observations by other investigators.  相似文献   

Period of delta Ceti     

Vijay Mohan 《Astrophysics and Space Science》1981,76(1):83-85

A period analysis of Ceti has been carried out and it has been found that the period of Ceti is increasing at a rate of 0.86 s per century. It is concluded that in its post-Main-Sequence evolution Ceti is in the early shell hydrogen-burning phase.  相似文献   

Formation of a shelfbreak front by freshwater discharge     

Chandrasekher Narayanan  Richard W. Garvine   《Dynamics of Atmospheres and Oceans》2002,36(1-3)

The circulation and transport of freshwater generated by an idealized buoyant source is studied using a three-dimensional primitive equation model. Freshwater enters the continental shelf, turns anticyclonically and moves downstream in the direction of Kelvin wave propagation. In the region close to the source, the flow reaches an equilibrium in the bottom boundary layer so that freshwater does not spread offshore any further. This offshore equilibrium distance increases as we move downstream until the freshwater is able to feel the presence of the shelfbreak. A shelfbreak front forms and the shelfbreak prevents any further offshore spreading of freshwater in the bottom boundary layer.Two complimentary mechanisms are responsible for the slow cross-shelf migration of freshwater and subsequent trapping of shelfbreak fronts: bottom stress and topographic changes. The shelfbreak creates an active, dynamic process preventing leakage from the continental shelf region to the slope region. However, the dynamical process that traps the front to the shelfbreak is still unclear.The location of the shelfbreak front depends on four dimensionless parameters: scaled inlet volume transport, scaled breadth, scaled “diffusivity” and scaled shelf width. We develop empirical relations for predicting the location of the frontal bottom intersection, given these parameters.  相似文献   

Intercomparison of IRS-P4-MSMR derived geophysical products with DMSP-SSM/I and TRMM-TMI finished products     

A. K. Varma  R. M. Gairola  A. K. Mathur  B. S. Gohil  Vijay K. Agarwal 《Journal of Earth System Science》2002,111(3):247-256

In this paper, MSMR geophysical products like Integrated Water Vapour (IWV), Ocean Surface Wind Speed (OWS) and Cloud Liquid Water (CLW) in different grids of 50, 75 and 150 kms are compared with similar products available from other satellites like DMSP-SSM/I and TRMMTMI. MSMR derived IWV, OWS and CLW compare well with SSM/I and TMI finished products. Comparison of MSMR derived CLW with that derived from TMI and SSM/I is relatively in less agreement. This is possibly due to the use of 37 GHz in SSM/I and TMI that is highly sensitive to CLW, while 37 GHz channels are not available on MSMR. Monthly comparison of MSMR geophysical products with those from TMI is all carried out for climatological purpose. The monthly comparisons were much better compared to instantaneous comparisons. In this paper, details of the data analysis and comparison results are presented. The usefulness of the MSMR vis-à-vis other sensors is also discussed.  相似文献   

Modeling hydrodynamics and aquaculture waste transport in coastal maine     

Vijay Panchang  G. Cheng  Carter Newell 《Estuaries and Coasts》1997,20(1):14-41

Net-pen aquaculture results in the introduction of excess fish food and fecal matter in coastal waters. These wastes may modify the benthic environment. Mathematical models are developed in this study to simulate tidal and wind-driven currents, waves, and the resulting dispersion of fish food and fecal matter in coastal Maine, a region where limited modelling studies have been performed. Cobscook Bay and Toothacher Bay in Maine are studied in detail through the use of mathematical models and field data. We find that a systematic, site-specific, step-by-step modeling strategy involving the use of numerical models to simulate the overall hydrodynamic environment in combination with a waste-particle transport model can be an extremely powerful method of determining a priori whether aquaculture operations will cause high rates of net-pen waste accumulation at a particular site.  相似文献