Numerical modeling of extreme sea levels associated with tropical cyclones in the Indian seas has been confined to the northern part of the Bay of Bengal (north of Tamil Nadu). However, limited attempts have been made for modeling of surges along the Tamil Nadu and Sri Lankan coasts. Although, very rarely, cyclones form south of 10°N, there are some instances of severe cyclonic storms hitting these areas and causing widespread destruction to life and property. Keeping this in view, a suitable location-specific, high-resolution, numerical model has been developed for the prediction of storm surges in these regions with a grid resolution of 3 km. Using the model, numerical experiments are performed to simulate the storm surge associated with the 1964 Rameswaram cyclone, the 1978 Batticaloa cyclone, the 1992 Tuticorin cyclone, the 1993 Karaikal cyclone, and the 1994 Madras cyclone. During the years 1964, 1978, and 1992, the cyclones struck both Sri Lanka and Tamil Nadu coasts, while in 1993 and 1994, the cyclones struck only the Tamil Nadu coast. It is found that the computed sea surface elevations are in close agreement with the available observations/estimates. 相似文献
The PUMA (Pull-Up Multichannel Array) is a sea-bottom instrument for remotely recording data from a 12 channel hydrophone array. Its purpose is to achieve (i) denser data coverage, leading to (ii) improved velocity analysis and (iii) multichannel processing of wide angle seismic data collected on the continental shelf. The instrument consists of a 1.2 km array terminating with a pressure case in which 8 FM cassette recorders, a power supply, microprocessor controller and internal clock are housed. It can be pre-programmed to switch on during shot windows for a total of four hours recording time.The PUMA was successfully used in an experiment west of Lewis, Outer Hebrides, U.K. in August–September 1984. We show an example of PUMA data from this experiment. Indications are that the instrument will provide improved constraints on seismic velocities in the lower continental crust and uppermost mantle. 相似文献
A depth-averaged numerical model has been developed to study tidal circulation and suspended sediment transport in the Gulf of Kachchh including Kandla creek, west coast of India. The resolution of the model is taken as 750 m × 750 m, which is found to be adequate for the gulf region. However, this resolution could not produce the realistic circulation pattern and suspended sediment concentration in the Kandla creek region. There is a major seaport at Kandla which serves as the sea gate to northwest India. Therefore, a 2-D fine resolution (75 m × 75 m) model for Kandla creek has been developed and coupled with the coarser gulf model to compute the flow features in the creek region. The model dynamics and basic formulation remain the same for both the gulf model and the creek model. The models are barotropic, based on shallow water equations, and neglect horizontal diffusion and wind stress terms in the momentum equations. The models are fully nonlinear and use a semiexplicit finite difference scheme to solve mass, momentum, and advection-diffusion equations in a horizontal plane. The tide in the gulf is represented in the model by the semidiurnal M2 constituent mainly. In this study, no fresh water discharge conditions have been considered so the results are appropriate for the dry season. Numerical experiments are carried out to study the circulation and suspended sediment concentrations in the gulf and the creek regions. The computed results are validated with the available observations. 相似文献
Artificial neural networks have a wide application in many areas of science and engineering and, particularly, in geotechnical
problems with some degree of success due to the fact that the mechanical behavior of rocks are not salient. They are highly
nonlinear, quite complex and complicated. While applying neural network in such complicated problems, epoch determination
is based on hit-and-trail basis mainly. In this paper, the effect of different number of epochs is shown on the network and
a method is proposed to determine the optimum number of epoch with the help of self-organized map (SOM) to avoid overtraining
of the network. Data distribution is also done with the help of SOM and a statistical analysis is made to show consistency
between training and testing dataset for ensuring the optimal model performance. 相似文献
This study assesses the disparity in the level of material wellbeing between the rural and urban areas of various districts of West Bengal. To measure the level of material wellbeing three broad domains comprising of Housing index (HI), Basic Amenities Index (BAI) and Asset Index (AI) following which a composite index (Material Wellbeing Indexi.e. MWI) was computed for the urban and the rural areas for all the districts between the time frame of 2001–2011. A set of 14 sub-indicators were selected for the analysis. This paper takes into account the differentials between the urban and the rural areas of the state. The data was subjected to correlation analysis, ANOVA and PCA, intra-zonal analysis was also performed. The results show the presence of widespread levels of disparity between the various districts as well as within the districts. Over the course of the years this disparity has increased in case of the northern zone however intra and inter zonal disparity runs high. Among the different sub-indicators, BAI has recorded the highest decrease in the differentials whereas the AI has recorded the highest increase in the differentials. Among the districts eight of them have recorded a net increase in the differentials in MWI among which Maldah has recorded the highest decrease in the differentials whereas Dakshin Dinajpur has recorded the highest increase in the differentials.
Geotechnical and Geological Engineering - The Lengpui-Aizawl highway in the Northeastern part of India has witnessed several rockfall events in the past decades. This is the only highway that... 相似文献
Summary A comparative study was performed to evaluate the performance of the UK Met Office’s Global Seasonal (GloSea) prediction General
Circulation Model (GCM) for the forecast of maximum surface air temperature (Tmax) over the Indian region using the model generated hindcast of 15-members ensemble for 16 years (1987–2002). Each hindcast
starts from 1st January and extends for a period of six months in each year. The model hindcast Tmax is compared with Tmax obtained from verification analysis during the hot weather season on monthly and seasonal scales from March to June.
The monthly and seasonal model hindcast climatology of Tmax from 240 members during March to June and the corresponding observed climatology show highly significant (above 99.9% level)
correlation coefficients (CC) although the hindcast Tmax is over-estimated (warm bias) over most parts of the Indian region. At the station level over New Delhi, although the forecast
error (forecast-observed) at the monthly scale gradually increases from March to June, the forecast error at the seasonal
scale during March to May (MAM) is found to be just 1.67 °C. The GloSea model also simulates well Tmax anomalies on monthly and seasonal scales during March to June with the lower Root Mean Square Error (RMSE) of bias corrected
forecast (less than 1.2 °C), which is much less than the corresponding RMSE of climatology (reference) forecast. The anomaly
CCs (ACCs) over the station in New Delhi are also highly significant (above 95% level) on monthly to seasonal time scales
from March to June, except for April.
The skill of the GloSea model for the seasonal forecast of Tmax as measured from the ACC map and the bias corrected RMSE map is reasonably good during MAM and April to June (AMJ) with higher
ACC (significant at 95% level) and lower RMSE (less than 1.5 °C) found over many parts of the Indian regions.
Authors’ addresses: D. R. Pattanaik, H. R. Hatwar, G. Srinivasan, Y. V. Ramarao, India Meteorological Department (IMD), New
Delhi, India; U. C. Mohanty, P. Sinha, Centre for Atmospheric Sciences, Indian Institute of Technology, Hauz Khas, New Delhi
110016, India; Anca Brookshaw, UK Met Office, UK. 相似文献
Construction of the Farakka barrage on the Ganga River in April 1975 to augment water supply to the Calcutta port has brought about a significant increase in freshwater discharge in its distributary, the Hoogly estuary. This has naturally resulted in major changes in the ecology of this estuary, causing modifications in the structure of its fishery resources, fishing pattern, and fish production. This paper presents observations on salinity, plankton, bottom biota, fishery resource, and fish production of different zones of the Hooghly estuary during the period 1982–1992. Comparison with similar studies made before and immediately after commissioning of the Farakka barrage (1975–1977) has revealed that the increased freshwater discharge has resulted in considerable decrease in salinity throughout the estuary. The freshwater zone now extends toward the mouth of the estuary. The true estuarine zone has moved seaward and the marine zone has been restricted to the area near the mouth of the estuary. This has effected major changes in plankton dynamics, sharp decline in the fishery of marine and neritic species in the upper estuary, caused a significant increase in catch ofTenualosa ilisha and an over twofold increase in the average annual fish landings from the estuary as a whole. New zonations have been proposed based on the presently, observed salinity values, which are the most significant factor in determining the fishery of any estuary. An interdisciplinary study of the ecology of the new zones is needed to establish their correct biological characteristics. 相似文献