Simulating Solar Cycles in Northern and Southern Hemispheres by Assimilating Magnetic Data into a Calibrated Flux-Transport Dynamo     

Mausumi Dikpati  Peter A. Gilman  Giuliana de Toma  Siddhartha S. Ghosh 《Solar physics》2007,245(1):1-17

We use the flux-transport dynamo prediction scheme introduced by Dikpati, de Toma, and Gilman (Geophys. Res. Lett. 33, L05102, 2006) to make separate simulations and predictions of sunspot cycle peaks for northern and southern hemispheres. Despite the division of the data, the skill level achieved is only slightly lower than that achieved for the sum of both hemispheres. The model shows skill at simulating and predicting the difference in peaks between North and South, provided that difference is more than a few percent. The simulation and prediction skill is achieved without adjustment to any parameters of the model that were used when peaks for the sum of North and South sunspot areas was simulated. The results are also very insensitive to the averaging length applied to the input data, provided the simulations and predictions are for peaks defined by averaging the observations over at least 13 rotations. However, in its present form, the model is not capable of skillfully simulating or predicting short-time-scale features of individual solar cycles.  相似文献   

Geochemistry of some banded iron-formations of the Archean supracrustals,Jharkhand-Orissa region,India     

H. N. Bhattacharya  Indranil Chakraborty  Kaushik K. Ghosh 《Journal of Earth System Science》2007,116(3):245-259

Banded iron-formations (BIF) form an important part of the Archean supracrustal belts of the Jharkhand-Orissa region, India. Major, trace and REE chemistry of the banded iron-formation of the Gandhamardan, Deo Nala, Gorumahisani and Noamundi sections of the Jharkhand-Orissa region are utilized to explore the source of metals and to address the thermal regime of the basin floor and the redox conditions of the archean sea. Hydrothermal fluids of variable temperatures might have contributed the major part of the Fe and other trace elements to the studied banded iron-formations. Diagenetic fluids from the sea floor sediments and river water might have played a subdued role in supplying the Fe and other elements for the banded iron-formations.  相似文献   

Probes of cosmic star formation history     

Pranab Ghosh 《Journal of Astrophysics and Astronomy》2002,23(1-2):107-113

I summarize X-ray diagnostic studies of cosmic star formation history in terms of evolutionary schemes for X-ray binary evolution in normal galaxies with evolving star formation. Deep X-ray imaging studies byChandra andXMM-Newton are now beginning to constrain both the X-ray luminosity evolution of galaxies and the logN- logS diagnostics of the X-ray background. I discuss these in the above context, summarizing current understanding and future prospects.  相似文献   

C-O bonds in carbonate minerals: A new kind of paleothermometer     

Prosenjit Ghosh  Jess Adkins  Brian Balta  Edwin A. Schauble  John M. Eiler 《Geochimica et cosmochimica acta》2006,70(6):1439-1456

The abundance of the doubly substituted CO₂ isotopologue, ¹³C¹⁸O¹⁶O, in CO₂ produced by phosphoric acid digestion of synthetic, inorganic calcite and natural, biogenic aragonite is proportional to the concentration of ¹³C-¹⁸O bonds in reactant carbonate, and the concentration of these bonds is a function of the temperature of carbonate growth. This proportionality can be described between 1 and 50 °C by the function: Δ₄₇ = 0.0592 · 10⁶ · T⁻² − 0.02, where Δ₄₇ is the enrichment, in per mil, of ¹³C¹⁸O¹⁶O in CO₂ relative to the amount expected for a stochastic (random) distribution of isotopes among all CO₂ isotopologues, and T is the temperature in Kelvin. This relationship can be used for a new kind of carbonate paleothermometry, where the temperature-dependent property of interest is the state of ordering of ¹³C and ¹⁸O in the carbonate lattice (i.e., bound together vs. separated into different CO₃²⁻ units), and not the bulk δ¹⁸O or δ¹³C values. Current analytical methods limit precision of this thermometer to ca. ± 2 °C, 1σ. A key feature of this thermometer is that it is thermodynamically based, like the traditional carbonate-water paleothermometer, and so is suitable for interpolation and even modest extrapolation, yet is rigorously independent of the δ¹⁸O of water and δ¹³C of DIC from which carbonate grew. Thus, this technique can be applied to parts of the geological record where the stable isotope compositions of waters are unknown. Moreover, simultaneous determinations of Δ₄₇ and δ¹⁸O for carbonates will constrain the δ¹⁸O of water from which they grew.  相似文献   

Combined effects of water pH and alkalinity on the accumulation of lead, cadmium and chromium to Labeo rohita (Hamilton)     

S. Adhikari Ph.D.  L. Ghosh Ph.D.  S. Ayyappan Ph.D. 《International Journal of Environmental Science and Technology》2006,3(3):289-296

Influence of pH (5.5, 7.0 and 8.5) and alkalinity (40 to 200 mg/L as CaCO₃) on the accumulation of Pb (NO₃)₂ CdCl₂, H₂O and K₂Cr₂O₇ to Labeo rohita (Hamilton) was investigated in the laboratory. Highest accumulation of Pb and Cr in whole fish occurred at pH 5.5 and at alkalinity level of 40 to 46 mg/L as CaCO₃ compared to 7.0 and 8.5. In case of Cd maximum accumulation occurred at pH 7.0 and at alkalinity of 100 mg/L as CaCO₃ than that of pH 5.5 and 8.5 and alkalinity 42 and 156 mg/L as CaCO₃. Maximum accumulation of lead and chromium occurred at total alkalinity level of 40 and 46 mg/L as CaCO₃, respectively while maximum accumulation of cadmium occurred at an alkalinity level of 200 mg/L as CaCO₃. A significant (p<0.05) linear relationship was demonstrated between increasing pH/ alkalinity and decreasing accumulation in Pb and Cr treatment at all exposure period while for Cd there was no significant linear relationship established.  相似文献   

Far-infrared brightness temperature of Saturn's disk and rings     

R.R. Daniel  S.K. Ghosh  K.V.K. Iyengar  T.N. Rengarajan  S.N. Tandon  R.P. Verma 《Icarus》1982,49(2):205-212

We present far-infrared observations of Saturn in the wavelength band 76–116 μm, using a balloon-borne 75-cm telescope launched on 10 December 1980 from Hyderabad, India, when B′, the Saturnicentric latitude of the Sun, was 4°.3. Normalizing with respect to Jupiter, we find the average brightness temperature of the disk-ring system to be 90 ± 3° K. Correcting for the contribution from rings using experimental information on the brightness temperature of rings at 20 μm, we find T_D, the brightness temperature of the disk, to be 96.9 ± 3.5° K. The systematic errors and the correction for the ring contribution are small for our observations. We, therefore, make use of our estimate of T_D and earlier observations of Saturn when contribution from the rings was large and find that for wavelengths greater than 50 μm, there is a small reduction in the ring brightness temperature as compared to that at 20 μm.  相似文献   

Influence of fluvial‐tidal interactions on the nature of cross‐stratified packages in a deltaic setting: examples from the Barakar Coal Measure (Permian), Satpura Gondwana Basin,central India     

Sanjoy Kumar Ghosh  Chandan Chakraborty  Tapan Chakraborty 《Geological Journal》2005,40(1):65-81

Nine different types of cross‐stratified packages from the coal‐bearing, deltaic succession of the Barakar Formation (Permian) of the Satpura Gondwana Basin, central India, are described. The deposits are characterized by periodic mudstone drapes, reactivation surfaces including all other features suggestive of deposition from periodically unsteady, tidally‐influenced flows. The inferred flow patterns varied from purely bidirectional to pulsating unidirectional. The different types of cross‐stratified packages are interpreted to have resulted from superimposition of ebb‐oriented, steady, unidirectional fluvial currents of variable strength on the tidal flow in a deltaic setting. The study helps to distinguish cross‐strata that may develop in settings where fluvial and tidal currents interact. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

Identification of flood seasonality and drivers across Canada     

Jitendra Singh  Subimal Ghosh  Slobodan P. Simonovic  Subhankar Karmakar 《水文研究》2021,35(10):e14398

Floods are the most frequently occurring natural hazard in Canada. An in-depth understanding of flood seasonality and its drivers at a national scale is essential. Here, a circular, statistics-based approach is implemented to understand the seasonality of annual-maximum floods (streamflow) and to identify their responsible drivers across Canada. Nearly 80% and 70% of flood events were found to occur during spring and summer in eastern and western watersheds across Canada, respectively. Flooding in the eastern and western watersheds was primarily driven by snowmelt and extreme precipitation, respectively. This observation suggests that increases in temperature have led to early spring snowmelt-induced floods throughout eastern Canada. Our results indicate that precipitation (snowmelt) variability can exert large controls on the magnitude of flood peaks in western (eastern) watersheds in Canada. Further, the nonstationarity of flood peaks is modelled to account for impact of the dynamic behaviour of the identified flood drivers on extreme-flood magnitude by using a cluster of 74 generalized additive models for location scale and shape models, which can capture both the linear and nonlinear characteristics of flood-peak changes and can model its dependence on external covariates. Using nonstationary frequency analysis, we find that increasing precipitation and snowmelt magnitudes directly resulted in a significant increase in 50-year streamflow. Our results highlight an east–west asymmetry in flood seasonality, indicating the existence of a climate signal in flood observations. The understating of flood seasonality and flood responses under the dynamic characteristics of precipitation and snowmelt extremes may facilitate the predictability of such events, which can aid in predicting and managing their impacts.  相似文献   

Comprehensive evaluation of the changing drought characteristics in Bundelkhand region of Central India   总被引：1，自引：0，他引：1  

T. Thomas  R. K. Jaiswal  P. C. Nayak  N. C. Ghosh 《Meteorology and Atmospheric Physics》2015,127(2):163-182

  相似文献   

Temperature control,emission abatement and costs: key EMF 27 results from Environment Canada’s Integrated Assessment Model     

Yunfa Zhu  Madanmohan Ghosh 《Climatic change》2014,123(3-4):571-582

This paper investigates the potential impacts of alternative international climate change scenarios based on different policies and technological circumstances on future emission pathways and abatement costs. It also examines if these hypothetical scenarios could result in significant emission reductions required to control the global temperature from rising to no more than 2.5 °C above preindustrial level. Using an integrated assessment model, this paper examines these issues under 12 scenarios derived from four policy perspectives and three technology dimensions. Results show that the no-policy-change baseline scenarios lead to high global average temperatures in the future. To control the temperature efficiently, every global region will be required to undertake considerable abatement efforts. Current country pledges alone, even if fully implemented, cannot control the global temperature in the future to within a comfortable zone. There will still be large gap between the reductions needed to meet the 2.5 degree objective, associated with 550 ppm and the reductions associated with existing abatement efforts. Further stringent policies together with favourable technological conditions may lead to the desired level of temperature control. Participation by only a subset of nations not only makes achieving the temperature goal difficult but also costly. To achieve temperature control efficiently, global coordination and full participation by all regions are necessary and global participation may reduce global abatement costs. It is worth noting that abatement costs vary widely across regions under different policy and technology scenarios.  相似文献