Recession of Milam Glacier,Kumaun Himalaya,Observed via Lichenometric Dating of Moraines     

Kapil Bisht  Yogesh Joshi  Shashi Upadhyay  Poonam Metha 《Journal of the Geological Society of India》2018,92(2):173-176

Glaciers being very sensitive to climate change have been identified as one of the best indicators of climate change and evidences have proved that most of the Himalayan glaciers have receded with an increased rate during the recent past under the influence of global warming. Lichenometric study was carried out on the moraines of Milam glacier (located in Pithoragarh district of Uttarakhand) with the help of lichen species Dimelaena oreina having an average annual growth rate of 1.31 mm. The study revealed that Milam glacier has receded 1450 m in last 69.37 years with an average recession rate of 20.90 m/year. Since lichenometric studies are cost effective and ecofriendly in comparison to carbon dating, satellite and remote sensing based studies and also reliable, hence, it should be promoted in Himalaya which is an abode of glaciers.  相似文献   

Carbon dioxide,water vapor and sensible heat fluxes over a tallgrass prairie     

Shashi B. Verma  Joon Kim  Robert J. Clement 《Boundary-Layer Meteorology》1989,46(1-2):53-67

Fluxes of CO₂, water vapor and sensible heat were measured in a grassland ecosystem near Manhattan, Kansas, employing the eddy correlation technique. The vegetation at this site is dominated by big bluestem (Andropogon gerardii), switchgrass (Panicum virgatum), and indiangrass (Sorghastrum nutans). Diurnal patterns of the energy budget components and CO₂ fluxes are evaluated on a few selected days. Influence of high atmospheric evaporative demand and low availability of soil water are examined on (a) energy partitioning, and (b) the magnitudes and patterns of atmospheric carbon dioxide exchange.Published as Paper No. 8470, Journal Series, Nebraska Agricultural Research Division.  相似文献   

Kolmogorov constants for CO2, wind velocity,air temperature,and humidity fluctuations over a crop surface     

Shashi B. Verma  Dean E. Anderson 《Boundary-Layer Meteorology》1984,28(1-2):161-167

The Kolmogorov constants for CO₂, wind velocity, air temperature, and humidity fluctuations were evaluated from measurements made over soybean and grain sorghum fields and found to be 0.78 ± 0.11, 0.49 ± 0.08, 0.70 ± 0.15, and 0.99 ± 0.16, respectively. These results are consistent with recent observations reported in the literature.Published as Paper No. 7255, Journal Series, Nebraska Agricultural Experiment Station. The work reported here was conducted under Regional Research Project 11-33 and Nebraska Agricultural Experiment Station Project 27-003.Associate Professor and Post Doctoral Research Associate, respectively, Center for Agricultural Meteorology and Climatology, Institute of Agriculture and Natural Resources, University of Nebraska, Lincoln, NE, U.S.A., 68583-0728.  相似文献   

Characteristics of air flow above and within soybean canopies     

Dennis D. Baldocchi  Shashi B. Verma  Norman J. Rosenberg 《Boundary-Layer Meteorology》1983,25(1):43-54

Air flow was observed above and within canopies of a number of kinds of soybeans. The Clark cultivar and two isolines of the Harosoy cultivar were studied in 1979 and 1980, respectively. Wind speed above the canopy was measured with cup anemometers. Heated thermistor anemometers were used to measure air flow within the canopy. Above-canopy air flow was characterized in terms of the zero-plane displacement (d), roughness parameter (z _o) and drag coefficient (C _d). d and z _o were dependent on canopy height but were independent of friction velocity in the range 0.55 to 0.75 m s^?1 · C _d for the various canopies ranged from 0.027 to 0.035. Greater C _d values were measured over an erectophile canopy than over a planophile canopy. C _d was not measurably affected by differences in leaf pubescence. Within-canopy wind profiles were measured at two locations: within and between rows. The wind profile was characterized by a region of great wind shear in the upper canopy and by a region of relatively weak wind shear in the middle canopy. Considerable spatial variability in wind speed was evident, however. This result has significant implications for canopy flow modeling efforts aimed at evaluating transport in the canopy. In the lower canopy, wind speed within a row increased with depth whereas wind speed between two rows decreased with depth. The wind speeds at the two locations tended to converge to a common value at a height near 0.10 m. The attenuation of within-canopy air flow was stronger in canopies with greater foliage density. Canopy flow attenuation seemed to decrease with increasing wind speed, suggesting that high winds distorted the shape of the canopy in such a manner that the penetration of wind into the canopy increased.  相似文献   

Eddy correlation measurements of methane flux in a northern peatland ecosystem   总被引：1，自引：0，他引：1  

Shashi B. Verma  Frank G. Ullman  David Billesbach  Robert J. Clement  Joon Kim  E. S. Verry 《Boundary-Layer Meteorology》1992,58(3):289-304

A pilot study to measure methane flux using eddy correlation sensors was conducted in a peatland ecosystem in north central Minnesota. A prototype tunable diode laser spectrometer system was employed to measure the fluctuations in methane concentration.The logarithmic cospectrum of methane concentration and vertical wind velocity fluctuations under moderately unstable conditions had a peak nearf = 0.10 (wheref is the nondimensional frequency) and was quite similar to the cospectra of water vapor and sensible heat. Daytime methane flux during the first two weeks of August ranged from 120 to 270 mg m^-2 day^-1. The temporal variation in methane fluxes was consistent with changes in peat temperature and water table elevation. Our results compared well with the range of values obtained in previous studies in Minnesota peatlands.These field observations demonstrate the utility of the micrometeorological eddy correlation technique for measuring surface fluxes of methane. The current state-of-the-art in tunable diode laser spectroscopy makes this approach practical for use in key ecosystems.Published as Paper No. 9556, Journal Series, Nebraska Agricultural Research Division.  相似文献   

Econometric analysis of the ship demolition market     

Sabine Knapp  Shashi N. Kumar  Anna Bobo Remijn   《Marine Policy》2008,32(6):1023-1036

The topic of ship recycling has obtained considerable attention during the last two decades for a variety of reasons with the likelihood of the adoption of a new international convention under the auspices of the International Maritime Organization (IMO). This study applies econometric modeling to a unique data set to provide insight into the dynamics of the ship recycling market. The data set contains information on 51,112 ships over 100 gt and includes 748,621 events over a period of 29 years. The analysis confirms a negative relationship of earnings and a positive relationship of scrap prices for all locations while Bangladesh seems to be more sensitive to changes in earnings than the other locations and more likely demolishes larger and older vessels. The results for flag and ownership vary across scrapping locations with Malta and Cyprus indicating potential importance from a registry perspective. The overall safety profile of a vessel seems to be less important towards the probability of a ship being scrapped. Possible implementation of the convention at EU level will mostly likely affect Turkey while non-ratification of one of the major flags will most likely affect China or Bangladesh.  相似文献   

Period–colour and amplitude–colour relations in classical Cepheid variables – II. The Galactic Cepheid models     

Shashi M. Kanbur  Chow-Choong Ngeow  J. Robert Buchler 《Monthly notices of the Royal Astronomical Society》2004,354(1):212-224

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A multiwavelength view of a classical T Tauri star CV Cha     

Jeewan Chandra Pandey  Subhajeet Karmakar  Arti Joshi  Saurabh Sharma  Shashi Bhushan Pandey  Anil Kumar Pandey 《天文和天体物理学研究(英文版)》2019,(1)

Using long-term optical, ultraviolet(UV) and X-ray data, we present a study of a classical T Tauri star CV Cha. The V-band light curve obtained from the All Sky Automated Survey(ASAS) shows short as well as long-term variability. The short-term variability could be due to rotational modulation of CV Cha. We derive the rotational period of 3.714 ± 0.001 d for CV Cha. UV light curves obtained from Swift also show the variations. X-ray light curves from XMM-Newton and Swift do not show any significant short as well as long-term variability. However, the light curve from Chandra appears to be variable, which could be due to the emergence of flaring activities. X-ray spectra from all observations are explained well by the single temperature plasma of 0.95 keV with X-ray luminosity of 1030.4erg s-1in the 0.5–7.5 keV energy band. It appears that variability in optical and UV bands could be due to the presence of both hot and cool spots on the surface, while X-ray emission is dominated by magnetic processes.  相似文献   

Geophysical anomalies associated with uranium mineralization from Beldih mine, South Purulia Shear Zone, India     

Animesh Mandal  Arkoprovo Biswas  Saurabh Mittal  William K. Mohanty  Shashi Prakash Sharma  Debashish Sengupta  Joydip Sen  A. K. Bhatt 《Journal of the Geological Society of India》2013,82(6):601-606

Beldih mine at the central part of the South Purulia Shear Zone (SPSZ) has been reported with low grade uranium-bearing formation within quartz-magnetite-apatite host in kaolinized formation. Therefore, the present integrated geophysical study with gravity, magnetic, radiometric, very low frequency electromagnetic (VLF) and gradient resistivity profiling methods around the known mineralized zones aimed at identifying the exact geophysical signatures and lateral extent of these uranium mineralization bands. The closely spaced gravity-magnetic contours over the low to high anomaly transition zones of Bouguer, reduced-to-pole magnetic, and trend surface separated residual gravity-magnetic anomaly maps indicate the possibility of high altered zone(s) along NW-SE direction at the central part of the study area. High current density plots of VLF method and the low resistive zones in gradient resistivity study depict the coincidence with low gravity, moderately high magnetic and low resistivity anomalies at the same locations. Moderate high radioactive zones have also been observed over these locations. This also suggests the existence of radioactive mineralization over this region. Along profile P2, drilled borehole data revealed the presence of uranium mineralization at a depth of ～100 m. The vertical projection of this mineralization band also identified as low gravity, low resistivity and high magnetic anomaly zone. Thus, the application of integrated geophysical techniques supported by geological information successfully recognized the nature of geophysical signatures associated with the uranium mineralization of this region. This enhances the scope of further integrated geophysical investigations in the unexplored regions of SPSZ.  相似文献   

Data-based modelling approach for variable density flow and solute transport simulation in a coastal aquifer   总被引：1，自引：1，他引：0  

Basant Yadav  Shashi Mathur  Sudheer Ch  Brijesh Kumar Yadav 《水文科学杂志》2018,63(2):210-226

Data-based models, namely artificial neural network (ANN), support vector machine (SVM), genetic programming (GP) and extreme learning machine (ELM), were developed to approximate three-dimensional, density-dependent flow and transport processes in a coastal aquifer. A simulation model, SEAWAT, was used to generate data required for the training and testing of the data-based models. Statistical analysis of the simulation results obtained by the four models show that the data-based models could simulate the complex salt water intrusion process successfully. The selected models were also compared based on their computational ability, and the results show that the ELM is the fastest technique, taking just 0.5 s to simulate the dataset; however, the SVM is the most accurate, with a Nash-Sutcliffe efficiency (NSE) ≥ 0.95 and correlation coefficient R ≥ 0.92 for all the wells. The root mean square error (RMSE) for the SVM is also significantly less, ranging from 12.28 to 77.61 mg/L.  相似文献