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931.
P. L. S. Rao U. C. Mohanty P. V. S. Raju Gopal Iyengar 《Journal of Earth System Science》2003,112(1):95-111
In this study, we present the mean seasonal features of the Indian summer monsoon circulation in the National Centre for Medium
Range Weather Forecasting (NCMRWF) global data assimilation and forecast system. The large-scale budgets of heat and moisture
are examined in the analyzed and model atmosphere. The daily operational analyses and forecasts (day 1 through day 5) produced
for the summer seasons comprising June, July and August of 1995 and 1993 have been considered for the purpose. The principal
aim of the study is two-fold. Primarily, to comprehend the influence of the systematic errors over the Indian summer monsoon,
secondarily, to analyze the performance of the model in capturing the interseasonal variability.
The heat and moisture balances show reduction in the influx of heat and moisture in the model forecasts compared to the analyzed
atmosphere over the monsoon domain. Consequently, the diabatic heating also indicates reducing trend with increase in the
forecast period. In effect, the strength of Indian summer monsoon, which essentially depends on these parameters, weakens
considerably in the model forecasts. Despite producing feeble monsoon circulation, the model captures interseasonal variability
realistically. Although, 1995 and 1993 are fairly normal monsoon seasons, the former received more rainfall compared to the
latter in certain pockets of the monsoon domain. This is clearly indicated by the analyzed and model atmosphere in terms of
energetics. 相似文献
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934.
P. Chittibabu S. K. Dube J. B. Macnabb T. S. Murty A. D. Rao U. C. Mohanty P. C. Sinha 《Natural Hazards》2004,31(2):455-485
Storm surges generated by the strong tangential wind stressesand normal atmospheric pressure gradients at the sea surface due to tropical cyclones (TC'S)have been studied with the goal of detecting any significant and systematic changes due to climatechange. Cyclone and storm surge data for the 19th and 20th centuries for the Bay of Bengalcoast of the state of Orissa in India are available to varying degrees of quality and detail,the data being more scientific since the advent of the India Meteorological Department in 1875.Based on more precise data for the period 1971 to 2000, statistical projections have been madeon the probable intensities of tropical cyclones for various return periods. The super cyclone ofOctober 29, 1999 (SC1999) appears to have a return period of about 50 years. The cyclones of1831, 1885 and possibly the one in 1895 could have been super cyclones. During the 19th century,there were 72 flooding events associated with cyclones, whereas in the 20th century therewere only 56 events. There was no observational evidence to suggest that there was an increaseeither in the frequency or intensity of cyclones or storm surges on the coast of Orissa. However,the impact of cyclones and surges is on the increase due to increase of population and coastalinfrastructure. 相似文献
935.
D. S. V. V. D. Prasad P. V. S. Rama Rao G. Uma S. Gopi Krishna K. Venkateswarlu 《Journal of Earth System Science》2005,114(4):437-441
Using the data of amplitude scintillations recorded at 244 MHz from the geostationary satellite, FLEETSAT (73‡E) at a low
latitude station, Waltair (17.7‡N, 83.3‡E, 20‡N dip), during the increasing sunspot activity period of 1997–2000, the effect
of the geomagnetic storms on the occurrence of ionospheric scintillations has been studied. A total of 60 SC storms studied
during this period, following the Aarons’ criterion, reveals that the local time of onset of the recovery phase of the geomagnetic
storms play an important role in the generation or inhibition of the ionospheric irregularities. Out of the 60 storms studied,
nearly 60 to 70% satisfied the categories I, II and III of Aarons’ criteria. However, in the remaining 30 to 40% of the cases,
no consistent results were observed. Thus, there is a necessity for further investigation of the effect of geomagnetic storms
on ionospheric irregularities, particularly with reference to the altitude variations of the F-layer (h’F) relating to the
changes in the local electric fields. 相似文献
936.
Over-exploitation of groundwater results in decline of water levels, leading to intrusion of salt water along the coastal
region, which is a natural phenomenon. A groundwater quality survey has been carried out to assess such phenomena along the
coast of Visakhapatnam, Andhra Pradesh, India. Brackish groundwaters are observed in most of the wells. The rest of the wells
show a fresh water environment. The factors responsible for the brackish groundwater quality with respect to the influence
of seawater are assessed, using the standard ionic ratios, such as Ca2+:Mg2+, TA:TH and Cl−:HCO−
3. Results suggest that the brackish nature in most of the groundwaters is not due to the seawater influence, but is caused
by the hydrogeochemical process. Some influence of seawater on the groundwater quality is observed along the rock fractures.
The combined effect of seawater and urban wastewaters is due to the inferior quality of groundwater in a few wells, where
they are at topographic lows close to the coast. 相似文献
937.
The Mahanadi River is one of the largest river systems in the east coast of Indiaand the estuary drains and communicates with the Bay of Bengal. The seasonallyvarying fresh water river discharge and the intrusion of salt water from the baydepend on the flow associated with the semi-diurnal component of the astronomicaltide (dominated by M2 component). A numerical model has been developed tosimulate and study the salinity structure, velocity profile, flow and circulation patternand have been compared with the observed data. A reasonably good agreement isnoticed between the model simulations and the observations. The model result hasbeen utilised to compute sediment load transport to the estuary channel over a tidalcycle as well as on a monthly time scale. The sediment load transport owing to monthlyclimatological rainfall is discussed and it is inferred that a dynamic equilibrium existson a long-term over good/bad monsoons. 相似文献
938.
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940.