Impact of sea surface temperature in modulating movement and intensity of tropical cyclones     

M. Mandal  U. C. Mohanty  P. Sinha  M. M. Ali 《Natural Hazards》2007,41(3):413-427

It is well recognized that sea surface temperature (SST) plays a dominant role in the formation and intensification of tropical cyclones. A number of observational/empirical studies were conducted at different basins to investigate the influence of SST on the intensification of tropical cyclones and in turn, modification in SST by the cyclone itself. Although a few modeling studies confirmed the sensitivity of model simulation/forecast to SST, it is not well quantified, particularly for Bay of Bengal cyclones. The present study is designed to quantify the sensitivity of SST on mesoscale simulation of an explosively deepening storm over the Bay of Bengal, i.e., Orissa super cyclone (1999). Three numerical experiments are conducted with climatological SST, NCEP (National Center for Environmental Prediction) skin temperature as SST, and observed SST (satellite derived) toward 5-day simulation of the storm using mesoscale model MM5. At model initial state, NCEP skin temperature and observed SST over the Bay of Bengal are 1–2°C warmer than climatological SST, but cooler by nearly 1°C along the coastline. Observed SST shows a number of warm patches in the Bay of Bengal compared with NCEP skin temperature. The simulation results indicate that the sea surface temperature has a significant impact on model-simulated track and intensity of the cyclonic storm. The track and intensity of the storm is better simulated with the use of satellite-observed SST.  相似文献   

Multiscale island injection genetic algorithms for groundwater remediation     

Eva Sinha  Barbara S. Minsker 《Advances in water resources》2007

Genetic algorithms have been shown to be powerful tools for solving a wide variety of water resources optimization problems. Applying these approaches to complex, large-scale water resources applications can be difficult due to computational limitations, especially when a numerical model is needed to evaluate different solutions. This problem is particularly acute for solving field-scale groundwater remediation design problems, where fine spatial grids are often needed for accuracy. Finer grids usually improve the accuracy of the solutions, but they are also computationally expensive. In this paper we present multiscale island injection genetic algorithms (IIGAs), in which the optimization algorithms have different multiscale populations working on different islands (groups of processors) and periodically exchanging information. This new approach is tested using a field-scale pump-and-treat design problem at the Umatilla Army Depot in Oregon, USA. The performance of several variations of this approach is compared with the results of a simple genetic algorithm. The new approach found the same solution as much as 81% faster than the simple genetic algorithm and 9–53% faster than other previously formulated multiscale strategies. These findings indicate substantial promise for multiscale IIGA approaches to improve solution of complex water resources applications at the field scale.  相似文献   

Dispersion and radial depth of investigation of borehole modes   总被引：2，自引：0，他引：2  

Bikash K. Sinha  Sergey Asvadurov 《Geophysical Prospecting》2004,52(4):271-286

Sonic techniques in geophysical prospecting involve elastic wave velocity measurements that are performed by placing acoustic transmitters and receivers in a fluid‐filled borehole. The signals recorded at the receivers are processed to obtain compressional‐ and shear‐wave velocities in the surrounding formation. These velocities are generally used in seismic surveys for the time‐to‐depth conversion and other formation parameters, such as porosity and lithology. Depending upon the type of transmitter used (e.g. monopole or dipole) and as a result of eccentering, it is possible to excite axisymmetric (n= 0) , flexural (n= 1) and quadrupole (n= 2) families of modes propagating along the borehole. We present a study of various propagating and leaky modes that includes their dispersion and attenuation characteristics caused by radiation into the surrounding formation. A knowledge of propagation characteristics of borehole modes helps in a proper selection of transmitter bandwidth for suppressing unwanted modes that create problems in the inversion for the compressional‐ and shear‐wave velocities from the dispersive arrivals. It also helps in the design of a transmitter for a preferential excitation of a given mode in order to reduce interference with drill‐collar or drilling noise for sonic measurements‐while‐drilling. Computational results for the axisymmetric family of modes in a fast formation with a shear‐wave velocity of 2032 m/s show the existence of Stoneley, pseudo‐Rayleigh and anharmonic cut‐off modes. In a slow formation with a shear‐wave velocity of 508 m/s, we find the existence of the Stoneley mode and the first leaky compressional mode which cuts in at approximately the same normalized frequency ωa/V_S= 2.5 (a is the borehole radius) as that of the fast formation. The corresponding modes among the flexural family include the lowest‐order flexural and anharmonic cut‐off modes. For both the fast and slow formations, the first anharmonic mode cuts in at a normalized frequency ωa/V_S= 1.5 approximately. Cut‐off frequencies of anharmonic modes are inversely proportional to the borehole radius in the absence of any tool. The borehole quadrupole mode can also be used for estimating formation shear slownesses. The radial depth of investigation with a quadrupole mode is marginally less than that of a flexural mode because of its higher frequency of excitation.  相似文献   

A.S. Issar, Climate Changes during the Holocene and their Impact on Hydrological Systems, Cambridge University Press, Cambridge (2003) ISBN 0521817269, 0521607736 (143pp., hardback £50.00, paperback (available from June 2004) £19.99).     

Rajiv Sinha 《Quaternary Science Reviews》2004,23(23-24):2550-2553

  相似文献   

Numerical Modelling of Storm Surge in the Head Bay of Bengal Using Location Specific Model   总被引：1，自引：1，他引：1  

S. K. Dube  P. Chittibabu  P. C. Sinha  A. D. Rao  T. S. Murty 《Natural Hazards》2004,31(2):437-453

The head Bay of Bengal region, which covers part of Orissa and west Bengal in India as well as Bangladesh, is one of the most vulnerable regions of extreme sea levels associated with severe tropical cyclones which cause extensive damage. There has been extensive loss of life and property due to extreme events in this region. Shallow nature of the Bay, presence of Ganga-Brahmaputra-Meghna deltaic system and high tidal range are responsible for storm surges in this region. In view of this a location specific fine resolution numerical modelis developed for the simulation of storm surges. To represent mostof the islands and rivers in this region a 3km grid resolution is adopted. Several numerical experiments are carried out to compute the storm surges using the wind stress forcings representative of 1974, 1985, 1988, 1989, 1991, 1994 and 1999 cyclones, which crossed this region. The model computed surges are in good agreement with the available observations/estimates.  相似文献   

Propagation of elastic waves in an infinite plate of transversely isotropic material in three dimensions     

Nirmal Kumar Sinha 《Pure and Applied Geophysics》1971,86(1):80-87

Summary Free oscillations in three dimensions of an infinite plate of transversely isotropic material are studied in this paper. The dependence of the wave-velocity on the frequency has been determined numerically for the first two modes of propagation only and plotted graphically.  相似文献   

Geochemical problems associated with deccan basalts     

R. C. Sinha 《Bulletin of Volcanology》1971,35(4):1015-1021

  相似文献   

On disturbances in a semi-infinite visco-elastic rod in a magnetic field     

Miss Hasirashi Sinha 《Pure and Applied Geophysics》1969,72(1):84-89

Summary The paper makes use of electromagnetic equations of Maxwell, the equations of mechanical motion together with stress and strain relation of a particular visco-elastic material, to determine the disturbances in it when excited by a magnetic field.  相似文献   

Propagation of Love waves in a non-homogeneous stratum of finite depth sandwitched between two semi-infinite isotropic media     

Nirmal Kumar Sinha 《Pure and Applied Geophysics》1967,67(1):65-70

  相似文献   

On plane waves in thermo-viscoelastic solids deformed by magnetic fields     

Dilip K. Sinha 《Pure and Applied Geophysics》1964,57(1):53-60

Summary In the present paper,Maxwell's electromagnetic equations together with the equation of motion of two types of viscoelastic solids have been used to deal with the propagation of magneto-thermoviscoelastic plane waves.  相似文献