The Effect of Relative Sunspot Numbers,Solar Flare Numbers and Variable Component of 10.7 cm Solar Flux on The Seasonal Variation of 6300 Å Line Intensity at Calcutta     

Midya  S. K.  Chattopadhyay  R.  Pal  C. M. 《Earth, Moon, and Planets》1997,77(2):93-97

The paper presents the seasonal variation of 6300 Å line intensity at Calcutta with relative sunspot number, solar flare number and variable component of 10.7 cm solar flux. A study has been made and important results have been obtained which are as follows. (i) Intensity of 6300 Å line shows periodic variation with relative sunspot number, solar flare number and variable component of 10.7 cm solar flux during the period 1984–1986 which is the secondary peak of the descending phase of 21st solar cycle. (ii) 6300 Å line intensity at Cachoeira Paulista station, taken by Sahai et al. (1988), also shows periodic variation with solar parameters during the period 1978–1980 which is the peak phase of the solar cycle. (iii) A possible explanation of such a type of variation is also presented.  相似文献   

A search for a consistent model for the electromagnetic spectrum of the Crab nebula     

Cowsik  R.  Pal  Yash  Rengarajan  T. N. 《Astrophysics and Space Science》1970,6(3):390-395

An attempt is made to search for a consistent model to explain the electromagnetic spectrum of the Crab nebula (Tau A). It is assumed that there is a continuous injection of electrons at the centre of the nebula with an energy spectrumE ^–1.54 as evidenced by radio data. This spectrum must steepen to a slope larger than 2 at some energyE _i in order to ensure that the energy input into electrons remains finite. The spectrum must also steepen beyond an energyE _c depending on the magnetic field because of synchrotron energy losses. Two types of models are considered: Class I, in which the whole nebula is characterised by a uniform magnetic field, and Class II, in which besides the general fieldH ₀, small filamentary regions of strong fieldH _s are postulated.In models of Class I, the best fit to the observed data is obtained whenE _t >E _c andH ₀5×10^–4 gauss. However, this predicts a decrease in X-ray source size beyond 40 KeV. There are two possibilities of Class II model depending on the residence time of electrons in strong field regions being small or large. The former case explains the flattening in the optical spectrum.Experiments to distinguish between the various models are indicated.Presented at the International Conference on Cosmic Rays, Budapest, 1969.  相似文献   

Correction of Gravimetric Geoid Using Symbolic Regression     

B. Paláncz  J. L. Awange  L. Völgyesi 《Mathematical Geosciences》2015,47(7):867-883

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Comparison of Kalpana-1 atmospheric motion vectors with other observations     

S. K. Deb  Inderpreet Kaur  C. M. Kishtawal  P. K. Pal 《Theoretical and Applied Climatology》2014,115(3-4):693-702

The operational derivation of atmospheric motion vectors (AMVs) using infrared (10.5–12.5 μm) and water vapor (6.3–7.1 μm) channels of successive geostationary satellite images started in the 1980s. Subsequently, AMVs have become an important component for operational numerical weather prediction throughout the globe for the last decade or so. In India, at the Space Applications Centre, Indian Space Research Organisation, the operational derivation of AMVs (infrared winds and water vapor winds) from the Indian geostationary satellite Kalpana-1 has been initiated a few years back. Recently, an L-band radar lower atmosphere wind profiler (LAWP) has been installed at the National Atmospheric Research Laboratory, Gadanki located at (13.58°N, 79.28°E) for continuous high-resolution wind measurements in the lower atmosphere. In this study, a comparison of Kalpana-1 AMVs with wind measurements from LAWP and radiosonde has been carried out for a period of one and a half years. The performances of Kalpana-1 AMVs are also assessed by a separate comparison of Meteosat-7 AMVs, derived at the European Organisation for the Exploitation of Meteorological Satellites, with wind measurements from LAWP and radiosonde. Both sets of comparison show that AMVs from Kalpana-1 and Meteosat-7 are comparable over the Indian Ocean region.  相似文献   

Height Assignment Improvement in Kalpana-1 Atmospheric Motion Vectors   总被引：1，自引：0，他引：1  

S. K. Deb  Steve Wanzong  C. S. Velden  Inderpreet Kaur  C. M. Kishtawal  P. K. Pal  W. P. Menzel 《Journal of the Indian Society of Remote Sensing》2014,42(4):679-687

The real-time operational use of atmospheric motion vectors (AMVs) at numerical weather prediction (NWP) centers in India are being adversely affected due to inaccurate height assignment of cloud tracers, especially in thin semi-transparent clouds. In India, the operational derivation of AMVs from the Indian geostationary satellite Kalpana-1 began few years ago. A statistical empirical method (SEM) of height assignment, based on a genetic algorithm, is currently used to estimate the height of the retrieved vectors from Kalpana-1. This method has many limitations. In this paper, attempts have been made to implement the widely used and well tested height assignment methods such as the infrared window (WIN) technique, the H₂O intercept, and the cloud base method in the Kalpana-1 AMV retrieval algorithm. The new height assignment algorithm significantly improves the statistics of the retrieved winds when compared to radiosondes, especially in high and mid levels winds.  相似文献   

Monsoon rainfall extreme indices and tendencies from 1954–2003 in Kerala,India     

Indrani Pal  Abir Al-Tabbaa 《Climatic change》2011,106(3):407-419

Climate change has the potential ability to alter the occurrence and severity of extreme events. Though predicting changes of such extreme events is difficult, understanding them is important to determine the impacts of climate change in various sectors. This paper presents the change in rainfall extremes in the monsoon season in south-west Indian peninsula. Daily rainfall data were analysed for the entire Kerala state in India to determine if the extreme rainfall had changed over the 50-year period. Several indices were derived from the data to identify the extreme rainfalls. The trends of all the extreme indices were assessed by parametric ordinary least square regression technique, which were tested for significance at 95% level. Results showed significant decrease in monsoon rainfall extremes in Kerala that would affect the tendency of change in seasonal total rainfall. This study provides a comprehensive knowledge on extreme monsoon precipitation in Kerala, which could also be employed to study changing climate at local scale in other regions.  相似文献   

Characteristics of aerosol optical depth and Ångström parameters over Mohal in the Kullu Valley of Northwest Himalayan Region,India     

Nand Lal Sharma  Jagdish Chand Kuniyal  Mahavir Singh  Manum Sharma  Raj Pal Guleria 《Acta Geophysica》2011,59(2):334-360

The measurements using a ground based multi wavelength radiometer (MWR) at Mohal (31°54′N, 77°07′E, 1154 m AMSL) in the Kullu valley of Northwestern Himalayan region show that the spectral aerosol optical depth (AOD) and turbidity coefficient, β, are high in summer, moderate in monsoon season, low in winter and lowest in autumn, while wavelength exponent, α, has an opposite trend. Average annual value of AOD at 500 nm is 0.24±0.01, 0.43±0.02, and 0.28±0.02; that of β is 0.14±0.01, 0.22±0.02, and 0.17±0.03; and that of α is 1.06±0.09, 1.16±0.10, and 0.86±0.13, respectively, for clear, hazy and partially clear sky days. The considerably greater value of β on hazy days indicates more coarse particles in mountain haze. The fractional asymmetry factor (AF) is more negative in summer and autumn months. The AOD and β have significantly positive correlation with temperature and wind speed, suggesting high AODs and turbidity on hot and windy days.  相似文献   

Formation of gold and silver sulfides from melts in the Ag-Au-S system: Experimental data     

G. A. Pal’yanova  Yu. V. Seryotkin  K. A. Kokh 《Doklady Earth Sciences》2011,436(1):42-46

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Lidar observations of subvisual atmospheric phenomena: Research note     

S.R. Pal  R.W. Bell  A.I. Carswell 《大气与海洋》2013,51(2):226-230

Abstract

The systematic error of a large ensemble of 72 ‐h forecasts, as produced by the Canadian Meteorological Centre's spectral model, is studied with particular emphasis on its seasonal and spatial character. By decomposing the error into wavenumber space, we show that most of the error manifests itself in the long planetary waves. We find that the model displays a large systematic error in zonal wavenumber one, which systematically moves westward during each integration.  相似文献   

Support vector machines‐based modelling of seismic liquefaction potential     

Mahesh Pal 《国际地质力学数值与分析法杂志》2006,30(10):983-996

This paper investigates the potential of support vector machines (SVM)‐based classification approach to assess the liquefaction potential from actual standard penetration test (SPT) and cone penetration test (CPT) field data. SVMs are based on statistical learning theory and found to work well in comparison to neural networks in several other applications. Both CPT and SPT field data sets is used with SVMs for predicting the occurrence and non‐occurrence of liquefaction based on different input parameter combination. With SPT and CPT test data sets, highest accuracy of 96 and 97%, respectively, was achieved with SVMs. This suggests that SVMs can effectively be used to model the complex relationship between different soil parameter and the liquefaction potential. Several other combinations of input variable were used to assess the influence of different input parameters on liquefaction potential. Proposed approach suggest that neither normalized cone resistance value with CPT data nor the calculation of standardized SPT value is required with SPT data. Further, SVMs required few user‐defined parameters and provide better performance in comparison to neural network approach. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献