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Sanjay Gosain Sanjiv Tiwari Jayant Joshi P. Venkatakrishnan 《Journal of Astrophysics and Astronomy》2008,29(1-2):107-111
The Solar Vector Magnetograph (SVM) at Udaipur Solar Observatory saw its first light in April 2005. The retrieval of vector fields from the imaging spectro-polarimetric observational data requires a substantial amount of computer post-processing. The GUI-based data reduction and analysis software have been developed to make the data processing pipeline user-friendly and less time-consuming. In this paper we describe these software packages. 相似文献
2.
P. N. Shukla N. Bhandari V. N. Nijampurkar D. Kameswara Rao V. M. K. Puri Sanjiv Sharma 《Journal of Earth System Science》1983,92(3):255-260
Vertical profiles of137Cs and210Pb have been determined in a 9 m column of ice from accumulation zone of Changme-Khangpu glacier in north Sikkim valley.137Cs activity varies from 4 to 22 dpm/ L. In many samples210Pb occurs at a level of 20 to 65 dpm/ L which is much higher than the expected fallout value.137Cs and210Pb activities correlate well with each other but not with the dust content. Possibility of210Pb production in the nuclear explosions is discussed. Several peaks appear in the depth profile of137Cs and210Pb which can be matched with Chinese atmospheric nuclear explosions with some phase difference if a uniform ice accumulation
rate of 0.7 m per year is assumed since 1969. 相似文献
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We perform large-eddy simulation (LES) of a moderately convective atmospheric boundary layer (ABL) using a prognostic subfilter-scale
(SFS) model obtained by truncating the full conservation equations for the SFS stresses and fluxes. The truncated conservation
equations contain production mechanisms that are absent in eddy-diffusivity closures and, thus, have the potential to better
parametrize the SFS stresses and fluxes. To study the performance of the conservation-equation-based SFS closure, we compare
LES results from the surface layer with observations from the Horizontal Array Turbulence Study (HATS) experiment. For comparison,
we also show LES results obtained using an eddy-diffusivity closure. Following past studies, we plot various statistics versus
the non-dimensional parameter, Λ
w
/Δ, where Λ
w
is the wavelength corresponding to the peak in the vertical velocity spectrum and Δ is the filter width. The LES runs are
designed using different domain sizes, filter widths and surface fluxes, in order to replicate partly the conditions in the
HATS experiment. Our results show that statistics from the different LES runs collapse reasonably and exhibit clear trends
when plotted against Λ
w
/Δ. The trends exhibited by the production terms in the modelled SFS conservation equations are qualitatively similar to those
seen in the HATS data with the exception of SFS buoyant production, which is underpredicted. The dominant production terms
in the modelled SFS stress and flux budgets obtained from LES are found to approach asymptotically constant values at low
Λ
w
/Δ. For the SFS stress budgets, we show that several of these asymptotes are in good agreement with their corresponding theoretical
values in the limit Λ
w
/Δ → 0. The modelled SFS conservation equations yield trends in the mean values and fluctuations of the SFS stresses and fluxes
that agree better with the HATS data than do those obtained using an eddy-diffusivity closure. They, however, underpredict
considerably the level of SFS anisotropy near the wall when compared to observations, which could be a consequence of the
shortcomings in the model used for the pressure destruction terms. Finally, we address the computational cost incurred due
to the use of additional prognostic equations. 相似文献
4.
Estimation of Hydraulic Conductivity Values In a Coastal Aquifer 总被引：3，自引：0，他引：3
5.
Hussaini Mohammad Salem Farahmand Asadullah Shrestha Sangam Neupane Sanjiv Abrunhosa Manuel 《Hydrogeology Journal》2022,30(1):59-78
Hydrogeology Journal - While the success and sustainability of managed aquifer recharge (MAR) strongly depends on many characteristics of the site, it is necessary to integrate the site... 相似文献
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7.
Sanjiv Kumar 《地球物理与天体物理流体动力学》2013,107(1-4):191-202
Abstract The growth rates of instabilities in these shear flows are bounded by the rate of shear and the relativistic y factor. It is also shown that (i) the Howard Semi-Circle theorem is still valid, and (ii) the critical layer lies in the flow. Beaming effects are taken into account. 相似文献
8.
This paper describes the integration of results from different feature extraction algorithms using spectral and spatial attributes to detect specific urban features. Methodology includes segmentation of IKONOS data, computing attributes for creating image objects and classifying the objects with fuzzy logic and rule-based algorithms. Previous research reported low class accuracies for two specific classes – dark and grey roofs. A modified per-field approach was employed to extract urban features. New rule-sets were used on image objects having similar or near-similar spectral and spatial characteristics. Different algorithms using spectral and spatial attributes were developed to extract specific urban features from a time-series of Multi-Spectral Scanner (MSS) (4 m × 4 m) IKONOS data. The modified approach resulted in a remarkable improvement in the accuracy of classes that registered low spectral seperability and therefore low accuracy. The spectral and spatial based classification model may be useful in mapping heterogeneous and spectrally similar urban features. 相似文献
9.
The central United States experienced a cooling trend during the twentieth century, called the “warming hole,” most notably in the last quarter of the century when global warming accelerated. The coupled simulations of the models that participated in the Coupled Model Intercomparison Project, Phases 3 and 5 (CMIP3/5), have been unable to reproduce this abnormal cooling phenomenon satisfactorily. An unrealistic representation of the observed phasing of the Pacific Decadal Oscillation (PDO)—one of the proposed forcing mechanisms for the warming hole—in the models is considered to be one of the main causes of this effect. The CMIP5’s uncoupled Atmospheric Model Intercomparison Project (AMIP) experiment, whose duration approximately coincides with the peak warming hole cooling period, provides an opportunity, when compared with the coupled historical experiment, to examine the role of the variation in Pacific Ocean sea surface temperature (SST) in the warming hole’s formation and also to assess the skill of the models in simulating the teleconnection between Pacific SST and the continental climate in North America. Accordingly, this study compared AMIP and historical runs in the CMIP5 suite thereby isolating the role of SST forcing in the formation of the warming hole and its maintenance mechanisms. It was found that, even when SST forcing in the AMIP run was “perfectly” prescribed in the models, the skill of the models in simulating the warming hole cooling in the central United States showed little improvement over the historical run, in which SST is calculated interactively, even though the AMIP run overestimated the anti-correlation between temperature in the central United States and the PDO index. The fact that better simulation of the PDO phasing in the AMIP run did not translate into an improved summer cooling trend in the central United States suggests that the inability of the coupled CMIP5 models to reproduce the warming hole under the historical run is not mainly a result of the mismatch between simulated and observed PDO phasing, as believed. 相似文献
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