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R. Raaj M. Ramalingam S. K. Ghosh U. C. Kothyari 《Journal of the Indian Society of Remote Sensing》2008,36(1):61-68
This article reports a preliminary work in which two site specific seasonal algorithms have been proposed for estimating the
suspended sediments concentration (SSC) from the digital numbers recorded on Indian Remote sensing Satellite, IRS-P4 Ocean
Colour Monitor (OCM) sensor. For estimation of SSC, the proposed algorithms utilize dark pixel deduction atmospheric correction
technique. The computations are performed with respect to north east monsoon phase situations of Palk Strait coastal stretch.
The algorithms performance was satisfactory during the north east monsoon period. Although the results obtained cannot be
generalized, we suggest that the authority of proposed algorithms can be extended to other seasons with the addition of more
temporal experimental validation data sets and with numeric constants adjusted to present existing conditions. (As this area
was severely affected by Tsunami, it may have dissimilar conditions at present). 相似文献
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Subramaniam S. Ravindra Babu Y. Rabindranath Bera Basheerullah Baig G. Viswanath P. V. Bajpai O. P. 《Journal of the Indian Society of Remote Sensing》2003,31(3):187-196
Journal of the Indian Society of Remote Sensing - A stationary, compact, spatially modulated Fourier Transform spectro-radiometer based on triangular, common path Sagnac interferometer has been... 相似文献
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Predictability of low frequency modes 总被引：4，自引：0，他引：4
T. N. Krishnamurti M. Subramaniam D. K. Oosterhof G. Daughenbaugh 《Meteorology and Atmospheric Physics》1990,44(1-4):63-83
Summary In this paper we propose a procedure for the extended integration of low frequency modes of the time scale of 30 to 50 days. A major limitation of the extended integrations arise from a contamination of low frequency modes as a result of energy exchanges from the higher frequency modes. In this study we show an example on the prediction of low frequency mode to almost a month which is roughly 3 weeks beyond the conventional predictability. This was accomplished by filtering the higher frequency modes from the initial state. The initial state included a time mean state and a low frequency mode. The sea surface temperature anomalies on this time scale and the annual cycle were also prescribed.The specific experiment relates to the occurrence of a dry and a wet spell in the monsoon region. The meridional passage of an anticyclonic circulation anomaly over the lower troposphere and the eastward passage of a negative velocity potential anomaly over the upper levels of the Indian monsoon, on this time scale, are reasonably predicted. The aforementioned experiment was carried out with the 1979 data sets of the global experiment. A second example during an anomalous southward propagation of the low frequency waves over the Indian monsoon region during 1984 was also reasonably predicted by this model. Suggestions for further experimentation on the predictability of low frequency modes are proposed.With 16 Figures 相似文献
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S. Prabaharan R. Manonmani M. Ramalingam R. Vidhya T. Subramani 《Arabian Journal of Geosciences》2013,6(1):109-114
Wetland is a kind of natural resource with fast dynamic changes. Around 50% of the earth’s wetlands are estimated to have already disappeared worldwide over the last hundred years through conversion to industrial, agricultural, and residential developments. It is important for wetland protection and management to accurately map the wetland distribution by remote sensing and GIS. A study of the water turbidity and water quality of the wetland is essential to assess the fitness of the water for various purposes—irrigation, drinking, other domestic use, and industry. In the present study, an attempt has been made to know the inland wetland of Salem taluk of Salem district and to monitor changes in turbidity conditions for post-monsoon and pre-monsoon seasons. With the IRS P6 LISS III satellite image, indices images were generated for the extraction of water spread boundary. An automatic determination method of the threshold was examined to produce masks for the extraction of turbidity, and a turbidity map was generated which classifies turbidity into high, medium, and low. From the analysis, it has been observed that the inland wetlands of post-monsoon constitute 489 ha of the study area, of which 21.3% is subjected to high turbidity. Pre-monsoon spread constitutes 362.81 ha, of which 15.7% is subjected to high turbidity in pre-monsoon. Thus, this study highlights the usefulness of remotely sensed data for wetland mapping, seasonal monitoring, and characterization. The result indicates that turbidity conditions are moderate and low in pre-monsoon and moderate in post-monsoon seasons. 相似文献
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S. N. Tandon J. B. Hutchings S. K. Ghosh A. Subramaniam G. Koshy V. Girish P. U. Kamath S. Kathiravan A. Kumar J. P. Lancelot P. K. Mahesh R. Mohan J. Murthy S. Nagabhushana A. K. Pati J. Postma N. Kameswara Rao K. Sankarasubramanian P. Sreekumar S. Sriram C. S. Stalin F. Sutaria Y. H. Sreedhar I. V. Barve C. Mondal S. Sahu 《Journal of Astrophysics and Astronomy》2017,38(2):28
The performance of the ultraviolet telescope (UVIT) on-board AstroSat is reported. The performance in orbit is also compared with estimates made from the calibrations done on the ground. The sensitivity is found to be within \(\sim \)15% of the estimates, and the spatial resolution in the NUV is found to exceed significantly the design value of \(1.8^{\prime \prime }\) and it is marginally better in the FUV. Images obtained from UVIT are presented to illustrate the details revealed by the high spatial resolution. The potential of multi-band observations in the ultraviolet with high spatial resolution is illustrated by some results. 相似文献
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M. Thamban S. S. Naik R. Mohan A. Rajakumar N. Basavaiah Witty D’Souza Sarita Kerkar M. M. Subramaniam M. Sudhakar P. C. Pandey 《Journal of Earth System Science》2005,114(5):443-452
Changes in the terrigenous sediment source and transport mechanisms during the late Quaternary have been investigated using
four sediment cores within the Indian sector of Southern Ocean, using the magnetic susceptibility (MS) and sedimentological
records. Sediments deposited during the Holocene and other interglacial periods were characterised by low MS, low sand content,
reduced ice-rafted detritus (IRD) input and increased illite possibly transported via hydrographic advection from the south.
The glacial intervals are characterised by high MS, high sand content, increased IRD input and reduced illite clays, derived
from both local as well as Antarctic sources. Significant reduction in clay fraction and illite content during glacials suggests
that the erosive and transporting capabilities of the deep and bottom waters could have reduced compared to the interglacial
times. The changes in terrigenous influx to this region were significantly influenced by the rhythmic glacial-interglacial
fluctuations in bottom circulation and the position of the Polar Front. 相似文献
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Some statistical properties of the summer monsoon seasonal rainfall for India during the last 100 years (1881–1980) are presented.
The most recent decade of 1971–1980 shows the lowest value of standard-decadal average monsoon rainfall (86.40 cm) and is
also characterised by the second highest value of coefficient of variation in monsoon rainfall (12.4 %). The combined last
two standard-decadal period of 1961–1980 was the period of the largest coefficient of variation and the lowest average monsoon
rainfall for India.
The possible influence of global climatic variability on the performance of the monsoon is also examined. Analyses of correlation
coefficient show that a statistically significant positive relationship with a time-lag of about six months exists between
monsoon rainfall and northern hemispheric surface air temperature. A cooler northern hemisphere during January/February leads
to a poor monsoon.
All the major drought years during the last 3 decades had much cooler January/February periods over the northern hemisphere—1972
having the coldest January/February with a temperature departure of −0.94°C and the most disastrous monsoon failure. 相似文献
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This study presents the influence of the addition of additives such as activated carbon, carbon tetra chloride, hydrogen peroxide, and potassium dichromate on ultrasonic reduction of pharmaceutical wastewater chemical oxygen demand (COD) under laboratory conditions. The addition of activated carbon increased the % COD reduction whereas the combined addition of activated carbon and H2O2/CCl4/K2Cr2O7 was found to show higher reduction. Among the various combinations investigated, the combined addition of activated carbon and CCl4 was found to be the best combination. However, the environmental and health problems associated with these chemicals limit the applicability of the process in an industrial level. Further investigation with this system showed that the initial pH and initial COD have significant influence on the removal rate. The data obtained were fitted with first order and Langmuir–Hinshelwood kinetic models. The values of the rate constants obtained indicated that the pharmaceutical wastewater can be treated efficiently by the proposed methods. 相似文献