Prediction and monitoring of monsoon intraseasonal oscillations over Indian monsoon region in an ensemble prediction system using CFSv2   总被引：1，自引：0，他引：1  

S. Abhilash  A. K. Sahai  N. Borah  R. Chattopadhyay  S. Joseph  S. Sharmila  S. De  B. N. Goswami  Arun Kumar 《Climate Dynamics》2014,42(9-10):2801-2815

An ensemble prediction system (EPS) is devised for the extended range prediction (ERP) of monsoon intraseasonal oscillations (MISO) of Indian summer monsoon (ISM) using National Centers for Environmental Prediction Climate Forecast System model version 2 at T126 horizontal resolution. The EPS is formulated by generating 11 member ensembles through the perturbation of atmospheric initial conditions. The hindcast experiments were conducted at every 5-day interval for 45 days lead time starting from 16th May to 28th September during 2001–2012. The general simulation of ISM characteristics and the ERP skill of the proposed EPS at pentad mean scale are evaluated in the present study. Though the EPS underestimates both the mean and variability of ISM rainfall, it simulates the northward propagation of MISO reasonably well. It is found that the signal-to-noise ratio of the forecasted rainfall becomes unity by about 18 days. The potential predictability error of the forecasted rainfall saturates by about 25 days. Though useful deterministic forecasts could be generated up to 2nd pentad lead, significant correlations are found even up to 4th pentad lead. The skill in predicting large-scale MISO, which is assessed by comparing the predicted and observed MISO indices, is found to be ~17 days. It is noted that the prediction skill of actual rainfall is closely related to the prediction of large-scale MISO amplitude as well as the initial conditions related to the different phases of MISO. An analysis of categorical prediction skills reveals that break is more skillfully predicted, followed by active and then normal. The categorical probability skill scores suggest that useful probabilistic forecasts could be generated even up to 4th pentad lead.  相似文献   

Experimental studies on three potassium-rich ultramafic rocks from Damodar Valley, East India     

A. K. Gupta  B. Chattopadhyay  W. S. Fyfe  M. Powell 《Mineralogy and Petrology》2002,74(2-4):343-360

Summary An experimental study on the phase relationships of three potassium-rich ultramafic rocks from the Damodar Valley, Gondawana basins, has been performed under upper mantle P–T conditions (1.0–2.5 GPa, 700–1200 °C). The Mohanpur lamproite and Satyanarayanpur minette, both from the Raniganj basins, have been investigated with the addition of 15 wt% H₂O. No water was added in the experiments done on an olivine minette from the Jarangdih coal mine, Bokaro Basin, which originally contains 15 wt% CO₂ and 2.86 wt% H₂O. In all cases, olivine is the liquidus phase followed by phlogopite. The subsolidus assemblage for the three rocks is a phlogopite-bearing harzburgite, associated with apatite, Mg-ilmenite and carbonates for the Jarangdih rock; apatite, chromian spinel and carbonates and priderite (only between 1.0 and 1.2 GPa) in the case of the Mohanpur lamproite, and finally apatite, chromian spinel, rutile, and carbonate in the Satyanarayanpur sample. Although orthopyroxene is absent in the natural potassium-rich ultramafic rocks, its presence in the run products of the Jarangdih rock is possibly related to a reaction between olivine and a CO₂-bearing fluid phase. The presence of orthopyroxene in the run products of Mohanpur and Satyanarayanpur rocks may be due to a reaction between K-feldspar, olivine and a vapour phase to produce phlogopite and orthopyroxene. On the basis of present experimental investigation and isotopic studies made by previous investigators, it has been suggested that these K-rich rocks have crystallized from melts derived by vein-plus-wall-rock melting of a phlogopite-bearing harzburgite source rock. Received December 15, 1999; revised version accepted June 17, 2001  相似文献   

New holographic dark energy in modified f(R) Horava-Lifshitz gravity     

Abdul Jawad  Surajit Chattopadhyay 《Astrophysics and Space Science》2014,353(1):293-299

In this paper, we study the new holographic dark energy model in the framework of modified f(R) Horava-Lifshitz Gravity. We apply correspondence scheme to construct model the in underlying scenario using power-law form of scale factor. To explore accelerated expansion of the universe, some well-known cosmological parameters (equation of state parameter and squared speed of sound) and cosmological planes (ω _Λ – \(\omega'_{\varLambda}\) and statefinder) are discussed for reconstructed model. It is interesting to conclude that these parameters represent phantom behavior of the universe with stable configuration. also, the cosmological planes show compatible results with recent observations for accelerated expansion of the universe.  相似文献   

Some studies on solar microwave bursts in relation to the phases of the associated Hα-flares and their spectral nature     

S. K. Sarkar  T. Chattopadhyay  M. K. Das Gupta 《Solar physics》1975,40(2):411-415

Occurrences of the flare-associated microwave bursts as well as their peak flux and energy excess spectra have been examined in relation to the pre- and post-maximum phases of the respective flares during the period 1969–72. Results obtained are: (i) about 76% of the flare-associated bursts occur in the pre-maximum phase and the remaining 24% occurs in the post-maximum phase irrespective of the flare classification, intensity-wise or area-wise; (ii) ‘impulsive’ and ‘gradual rise and fall’ bursts are relatively more important in the pre-maximum phase while ‘post burst increase’ bursts show comparatively higher occurrences in the post-maximum phase; (iii) peak flux and energy excess spectra of the concurrent microwave bursts in the pre-maximum phase of the flare are mostly of ‘inverted U’ and ‘increasing with frequency’ spectral types. Of these, ‘impulsive’ bursts are predominantly of the ‘inverted U’ and the ‘grf’ bursts are of the ‘increasing with frequency’ spectral type.  相似文献   

Mann–Kendall trend analysis of tropospheric ozone and its modeling using ARIMA     

Goutami Chattopadhyay  Parthasarathi Chakraborthy  Surajit Chattopadhyay 《Theoretical and Applied Climatology》2012,110(3):321-328

The present work reports studies on the spatial distribution of tropospheric ozone extending over both southern and northern hemispheres. This study is based on a univariate approach to the spatial data series obtained at regular spatial intervals. Mann?CKendall's (MK) trend analysis has been carried out to discern the trend within the spatial distribution of the tropospheric ozone, and it has been observed that in all seasons, except monsoon (JJAS), there is a linear trend within the spatial distribution. Studying both monthly and seasonal behavior through autoregressive integrated moving average (ARIMA), it has been revealed that ARIMA (0,2,2) can be used as a representative of the spatially distributed tropospheric ozone over southern and northern hemispheres. The representative model has been confirmed through the study of Willmott's index and prediction yield.  相似文献   

Holographic dark energy scenario and variable modified Chaplygin gas     

Surajit Chattopadhyay  Ujjal Debnath 《Astrophysics and Space Science》2009,319(2-4):183-185

In this letter, we have considered that the universe is filled with normal matter and variable modified Chaplygin gas. Also we have considered the interaction between normal matter and variable modified Chaplygin gas in FRW universe. Then we have considered a correspondence between the holographic dark energy density and interacting variable modified Chaplygin gas energy density. Then we have reconstructed the potential of the scalar field which describes the variable modified Chaplygin cosmology.  相似文献   

Magnetoelastic shear wave propagation in pre-stressed anisotropic media under gravity     

Nirmala Kumari  Amares Chattopadhyay  Abhishek K. Singh  Sanjeev A. Sahu 《Acta Geophysica》2017,65(1):189-205

The present study investigates the propagation of shear wave (horizontally polarized) in two initially stressed heterogeneous anisotropic (magnetoelastic transversely isotropic) layers in the crust overlying a transversely isotropic gravitating semi-infinite medium. Heterogeneities in both the anisotropic layers are caused due to exponential variation (case-I) and linear variation (case-II) in the elastic constants with respect to the space variable pointing positively downwards. The dispersion relations have been established in closed form using Whittaker’s asymptotic expansion and were found to be in the well-agreement to the classical Love wave equations. The substantial effects of magnetoelastic coupling parameters, heterogeneity parameters, horizontal compressive initial stresses, Biot’s gravity parameter, and wave number on the phase velocity of shear waves have been computed and depicted by means of a graph. As a special case, dispersion equations have been deduced when the two layers and half-space are isotropic and homogeneous. The comparative study for both cases of heterogeneity of the layers has been performed and also depicted by means of graphical illustrations.  相似文献   

Influence of magnetic effect,anisotropy, irregularity,initial stress and heterogeneity on propagation of SH-wave in an irregular pre-stressed magnetoelastic monoclinic sandwiched layer     

Abhishek Kumar Singh  Amrita Das  Amres Chattopadhyay  Sudarshan Dhua 《Arabian Journal of Geosciences》2017,10(13):284

Monoclinic materials viz. quartz, lithium niobate and lithium tantalate are among the most abundant materials, finding numerous applications throughout the technological world. Moreover, the presence of irregularity, initial stresses, anisotropy and heterogeneity in a material medium is obvious. These facts motivate the study of magnetoelastic SH-wave propagation in an irregular monoclinic sandwiched layer between a heterogeneous isotropic layer and an isotropic half space, all under initial stress. The heterogeneity in the uppermost layer is caused due to exponential variation in rigidity, density and initial stress in terms of space variable pointing vertically downward. The dispersion relation has been obtained using first-order perturbation technique. The substantial effect of wave number, anisotropy, irregularity, width ratio of the layers, horizontal compressive/tensile initial stresses, heterogeneity and monoclinic-magnetoelastic coupling parameter associated with sandwiched layer on phase velocity of SH-wave has been studied and depicted by means of graph. Comparative study made for the case when pre-stressed irregular sandwiched layer is monoclinic-magnetoelastic to the case when it is isotropic magnetoelastic layer is one of the major highlights of the current study.  相似文献   

Modeling and Prediction of Monthly Total Ozone Concentrations by Use of an Artificial Neural Network Based on Principal Component Analysis     

Surajit Chattopadhyay  Goutami Chattopadhyay 《Pure and Applied Geophysics》2012,169(10):1891-1908

In the work discussed in this paper we considered total ozone time series over Kolkata (22°34′10.92″N, 88°22′10.92″E), an urban area in eastern India. Using cloud cover, average temperature, and rainfall as the predictors, we developed an artificial neural network, in the form of a multilayer perceptron with sigmoid non-linearity, for prediction of monthly total ozone concentrations from values of the predictors in previous months. We also estimated total ozone from values of the predictors in the same month. Before development of the neural network model we removed multicollinearity by means of principal component analysis. On the basis of the variables extracted by principal component analysis, we developed three artificial neural network models. By rigorous statistical assessment it was found that cloud cover and rainfall can act as good predictors for monthly total ozone when they are considered as the set of input variables for the neural network model constructed in the form of a multilayer perceptron. In general, the artificial neural network has good potential for predicting and estimating monthly total ozone on the basis of the meteorological predictors. It was further observed that during pre-monsoon and winter seasons, the proposed models perform better than during and after the monsoon.  相似文献   

Dealing with the complexity of earthquake using neurocomputing techniques and estimating its magnitudes with some low correlated predictors     

Goutami Chattopadhyay  Surajit Chattopadhyay 《Arabian Journal of Geosciences》2009,2(3):247-255

Earthquake, being one of the most hazardous geophysical events, has fascinated the scientists all over the globe to investigate an efficient predictive methodology. In India, earthquake is not a rare event. Purpose of the present paper is to view the earthquake as a complex system and then to estimate the magnitude of earthquake over Indian subcontinent using artificial neural network with backpropagation learning. The day, month, and year of occurrence of the earthquake, latitude of the place, and the longitude of the place are considered as the predictor variables. After considering various sizes of the hidden layer, it has been found that artificial neural network in the form of multilayer perceptron with two hidden nodes and sigmoid nonlinearity can be used to anticipate the magnitude of earthquake over Indian subcontinent. The paper concludes with an outline for future work.  相似文献