排序方式: 共有31条查询结果,搜索用时 15 毫秒
21.
The summer monsoon of 1988 总被引:1,自引:0,他引:1
Dr. T. N. Krishnamurti H. S. Bedi M. Subramaniam 《Meteorology and Atmospheric Physics》1990,42(1):19-37
Summary Time averaged, monthly mean fields of a number of climate parameters such as sea surface temperature anomalies, outgoing longwave radiation anomalies, 200 mb velocity potential field, streamfunction anomaly at the lower and the upper troposphere and percentage rainfall amounts are presented, for the summer of 1988 over the regions of Asian summer monsoon. Above normal rainfall occurred over most of the Indian subcontinent, southeast Asia and eastern China during 1988. In comparison, 1987 was a drought year. This paper presents a comparison of some of the salient aforementioned parameters. The evolution of the planetary scale divergent motions and the streamfunction anomaly exhibit prominent differences during the life cycle of the monsoon in these two years. The velocity potential field exhibits a pronounced planetary scale geometry with the divergent outflows emanating from the monsoon region during 1988. The descending branches of these time averaged circulations are found over the Atlantic ocean to the west and over the eastern Pacific and North America to the east. The immense size of this circulation is indicative of an above normal monsoon activity. During 1987, the outflow center was located much further to the southeast over the western Pacific ocean. The longitudinal extent of the monsoonal divergent circulations were much smaller in 1987.The positive sea surface temperature anomaly of the El Nino year 1987 is seen to move westwards to the western Pacific in 1988, a warm anomaly also appears over the eastern equatorial Indian ocean and the Bay of Bengal at this time. The latter contributes to the supply of moisutre during the active monsoon season of 1988. The outgoing long wave radiation anomalies evolve with a westward propagation of strong positive anomalies from the central Pacific ocean consistent with the evolution of divergent circulation. The streamfunction anomalies basically show westerly zonal wind anomalies being replaced by easterly anomalies during 1988 over the upper troposphere of the monsoon region.The lower tropospheric streamfunction anomaly during the drought year 1987 showed a pronounced counter monsoon circulation. That feature was absent in 1988.With 11 Figures 相似文献
22.
Ponnusamy Senthil Kumar Subramaniam Ramalingam Ramasundaram Vijayakumar Abhinaya Selvaraj Dinesh Kirupha Arukkani Murugesan Subramanian Sivanesan 《洁净——土壤、空气、水》2012,40(2):188-197
This paper discusses about the adsorption of metal ions such as Cu(II), Cd(II), Zn(II), and Ni(II) from aqueous solution by sulfuric acid treated cashew nut shell (STCNS). The adsorption process depends on the solution pH, adsorbent dose, contact time, initial metal ions concentration, and temperature. The adsorption kinetics was relatively fast and equilibrium was reached at 30 min. The adsorption equilibrium follows Langmuir adsorption isotherm model. The maximum adsorption capacity values of the modified cashew nut shell (CNS) for metal ions were 406.6 mg/g for Cu(II), 436.7 mg/g for Cd(II), 455.7 mg/g for Zn(II), and 456.3 mg/g for Ni(II). The thermodynamic study shows the adsorption of metal ions onto the STCNS was spontaneous and exothermic in nature. The kinetics of metal ions adsorption onto the STCNS followed a pseudo‐second‐order kinetic model. The external mass transfer controlled metal ions removal at the earlier stages and intraparticle diffusion at the later stages of adsorption. A Boyd kinetic plot confirms that the external mass transfer was the slowest step involved in the adsorption of metal ions onto the STCNS. A single‐stage batch adsorber was designed using the Langmuir adsorption isotherm equation. 相似文献
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24.
A new method for semi-automatic identification of oil slick on ocean/sea surface from space borne imagery using optical power spectra has been suggested. This method is based on the fact that the presence of the oil slick in the ocean suppresses the normal wave pattern that will be present in the ocean area without oil slick and the power spectra of the image area having the oil slick will be devoid of the peak corresponding to the dominant wave. In addition, the general shape of the oil slick will increase the low frequency content in the power spectra. The method has been applied for test areas containing oil slicks and the results are encouraging. 相似文献
25.
With the availability of high spatial resolution space-borne sensors, the wave parameters like wave propagation direction, wavelength of the dominant wave etc., are estimated from the Fourier spectra of ocean scene imageries. The hybrid optical processor is the most suitable for the analysis of imageries, since it utilises the parallel processing capability of the optical processor for generating the Fourier spectra. An attempt has been made to use a hybrid processor with wedge-ring sampling detector array for the estimation of wave parameters and the results are encouraging. 相似文献
26.
We present the optical spectroscopic study of two classical Be stars, 59 Cyg and OT Gem obtained over a period of few months in 2009. We detected a rare triple-peak H α emission phase in 59 Cyg and a rapid decrease in the emission strength of H α in OT Gem, which are used to understand their circumstellar disks. We find that 59 Cyg is likely to be rapid rotator, rotating at a fractional critical rotation of ~0.80. The radius of the H α emission region for 59 Cyg is estimated to be R d/R ? ~ 10.0, assuming a Keplerian disk, suggesting that it has a large disk. We classify stars which have shown triple-peaks into two groups and find that the triple-peak emission in 59 Cyg is similar to ζ Tau. OT Gem is found to have a fractional critical rotation of ~0.30, suggesting that it is either a slow rotator or viewed in low inclination. In OT Gem, we observed a large reduction in the radius of the H α emission region from ~6.9 to ~1.7 in a period of three months, along with the reduction in the emission strength. Our observations suggest that the disk is lost from outside to inside during this disk loss phase in OT Gem. 相似文献
27.
L. Juneng F. T. Tangang C. J. C. Reason S. Moten W. A. W. Hassan 《Meteorology and Atmospheric Physics》2007,97(1-4):273-290
Summary In this study, a rare tropical cyclone Vamei was simulated using the non-hydrostatic version 3.6 of the Penn State University
(PSU) – National Center for Atmospheric Research (NCAR) mesoscale model MM5. This unusual cyclone was generated on 26 December
2001 in an area close to the equator in the southern part of the South China Sea. The model was integrated for 80 h from 0000
UTC 26 December 2001 to 1800 UTC 29 December 2001. To examine the model performance, several important simulated fields including
sea-level pressure, surface wind speed and precipitation were compared to observations. The model simulated track of the cyclone
was also compared to the best track provided by the Joint Typhoon Warning Center (JWTC). Overall, the model performed reasonably
well, particularly in simulating the cyclone track and precipitation amount and spatial distribution. The analysis of the
model output indicated the important role of the latent heat flux in the genesis and intensification of tropical cyclone Vamei. 相似文献
28.
Annapurni Subramaniam Bhuwan Chandra Bhatt 《Monthly notices of the Royal Astronomical Society》2007,377(2):829-834
We present a UBV CCD photometric study of four open clusters, NGC 7245, King 9, IC 166 and King 13, located between l = 90° and 135°. All are embedded in a rich Galactic field. NGC 7245 and King 9 are close together in the sky and have similar reddenings. The distances and ages are: NGC 7245, 3.8 ± 0.35 kpc and 400 Myr; King 9 (the most distant cluster in this quadrant), 7.9 ± 1.1 kpc and 3.0 Gyr. King 13 is 3.1 ± 0.3 kpc distant and 300 Myr old. King 9 and IC 166 (4.8 ± 0.5 kpc distant and 1 Gyr old) may be metal-poor clusters ( Z = 0.008) , as estimated from isochrone fitting. The average value of the distance of young clusters from the Galactic plane in the above longitude range and beyond 2 kpc (−47 ± 16 pc, for 64 clusters) indicates that the young disc bends towards the southern latitudes. 相似文献
29.
Ramli Nazir Hossein Moayedi Puspanathan Subramaniam Soheil Ghareh 《Arabian Journal of Geosciences》2017,10(23):515
Excessive total and differential settlement at the intersection of a surcharged prefabricated vertical drain (SPVD) and a rigid piled embankment on soft ground during the post-construction period leads to considerable time and costs being spent on repetitive remedial works in the future. This paper presents a sustainable design approach for high and long embankment filling on soft clay at the approach to the structure by introducing the intersection of an SPVD at the transition to a rigid piled embankment in order to regulate the differential settlement between the two conventional ground treatment approaches. This paper also presents a full-scale field study to validate the performance of the intersection of the SPVD at the transition to the rigid piled embankment. By introducing the intersection ground treatment, post-construction settlement and differential settlement are minimised significantly, while the post-construction total settlement at the rigid transition piled embankment (TPE) zone is reduced significantly by about 80 to 95% of the total settlement, as compared to a conventional TPE. 相似文献
30.
Palanidoss Subramaniam Mohanachandra Menon Sreenadh Subhadeep Banerjee 《Marine Georesources & Geotechnology》2016,34(7):603-616
The present article discusses the stress–strain behavior and critical state parameters of the dredged Chennai marine clay stabilized with low cement content (2.5–10%). A series of one-dimensional consolidation tests and consolidated undrained tri-axial tests are performed on the cement stabilized dredged Chennai marine clay to evaluate the critical state parameters (λ, κ, M, Г, N) for varying cement contents and curing days. The results show that the slope of the critical state line M increases with an increase in the cement content. The parameter λ for the treated marine clay increases up to a cement content of 7.5% followed by a reduction. The parameter κ decreases with the addition of cement content. Finally, empirical formulations are proposed to predict the critical state parameters as the functions of the cement's contents and curing days. 相似文献