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11.
A collision between the ships MSC Chitra and MV Khalijia 3 in the mouth region of Mumbai Harbour led to a leakage of around 800 t of fuel oil in August 2010, affecting the rocky intertidal region of Colaba. To evaluate the impact of this catastrophic event on the resident biota, a 15-month-long sampling programme was initiated in the oil-affected area immediately after the spill. Petroleum hydrocarbons in water and sediment organic carbon values were high just after the oil spill but subsequently decreased in the following months. In total, 70 macrobenthic taxa were identified. Univariate diversity indices indicated that while the ecological status of the site, albeit briefly, was affected during August 2010, a healthy environment prevailed subsequently. Cluster and multi-dimensional scale (MDS) analyses distinctly segregated the oil impacted monsoon months from the other sampling months. BIOENV analyses indicated that petroleum hydrocarbons and organic carbon were the anthropogenic parameters influencing macrobenthic community structure. Benthic Opportunistic Polychaetes Amphipods (BOPA) index was used to evaluate the ecological quality of the study area as the index is sensitive to oil pollution. Low BOPA values throughout the study period indicated that the environment was good with few opportunistic species. Comparison with past data revealed that the oil spill did not have long-term deleterious effects on the macrobenthic species diversity of this rocky beach, and reasons thereof are discussed. 相似文献
12.
U. Saravana Kumar Mohammad Arzoo Ansari Archana Deodhar 《Arabian Journal of Geosciences》2014,7(7):2667-2677
Springs are the only available source of water for domestic and agricultural use in mountainous regions of Dhouli Rao and Kandela in the Sirmaur district of Himachal Pradesh, India. These springs are mainly gravity, contact or fracture and solution tubular (Karst) type. Drying of springs during summer causes much hardship to the inhabitants of this region. Hence, environmental isotopes (2H, 18O, 3H) were employed along with hydrogeochemistry and geomorphology to identify the recharge zones of the drying springs. From the stable isotope data of rainwater, the altitude effect was estimated (?0.3?‰ for δ18O per 100 m elevation) and used to determine the recharge zones of the drying springs (+1,000 to +1,430 m amsl). The geo-morphological setting of the valley indicated that either check dam, contour bunding or levees structures with gabion method of rainwater conservation can be implemented to augment the recharge of the springs. 相似文献
13.
We present the results based on broad-band (VRI) polarimetric observations of a number of stars that are present towards the fields of already known bright polarised standard stars namely BD+59° 389, HD 19820, and HD 25443. These three relatively bright stars were observed continuously for various observing programs using ARIES Imaging Polarimeter (AIMPOL) attached with 1-m Sampurnanand Telescope (ST) since 2006 to correct for any polarisation position angle offset. Since AIMPOL is an imaging polarimeter with a field-of-view of ～8 arcmin diameter, we could get polarisation measurements of a number of relatively faint stars that are present within the field-of-view of the AIMPOL towards the above three bright polarised standards. Based on these compiled observations for a relatively long duration, we could examine the constancy of the degree of polarisation and position angles of them. With the help of some statistical tests, five stars in the field of BD+59° 389 and two stars in the field of HD 19820 have been identified as stars that could be used as additional polarised standard stars. Since these additional stars are relatively fainter than the known polarised standards, they could be observed with bigger aperture telescopes (like 2-m) without them getting saturated. 相似文献
14.
Archana Nair Nachiketa Acharya Ankita Singh U. C. Mohanty T. C. Panda 《Pure and Applied Geophysics》2013,170(11):1945-1967
In this study the predictability of northeast monsoon (Oct–Nov–Dec) rainfall over peninsular India by eight general circulation model (GCM) outputs was analyzed. These GCM outputs (forecasts for the whole season issued in September) were compared with high-resolution observed gridded rainfall data obtained from the India Meteorological Department for the period 1982–2010. Rainfall, interannual variability (IAV), correlation coefficients, and index of agreement were examined for the outputs of eight GCMs and compared with observation. It was found that the models are able to reproduce rainfall and IAV to different extents. The predictive power of GCMs was also judged by determining the signal-to-noise ratio and the external error variance; it was noted that the predictive power of the models was usually very low. To examine dominant modes of interannual variability, empirical orthogonal function (EOF) analysis was also conducted. EOF analysis of the models revealed they were capable of representing the observed precipitation variability to some extent. The teleconnection between the sea surface temperature (SST) and northeast monsoon rainfall was also investigated and results suggest that during OND the SST over the equatorial Indian Ocean, the Bay of Bengal, the central Pacific Ocean (over Nino3 region), and the north and south Atlantic Ocean enhances northeast monsoon rainfall. This observed phenomenon is only predicted by the CCM3v6 model. 相似文献
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16.
George Mathew Archana Nair T. K. Gundu Rao Kanchan Pande 《Journal of Earth System Science》2009,118(4):391-404
Thermal infrared spectroscopy is a powerful technique for the compositional analysis of geological materials. The spectral
feature in the mid-IR region is diagnostic of the mineralogy and spectral signatures of mixtures of minerals that add linearly,
and therefore, can be used as an important tool to determine the mineralogy of rocks in the laboratory and remotely for planetary
exploration. The greatest challenge in the emission measurement lies in the measurement of the weak thermal photons emitted
from geological materials in a laboratory setup, and accurately records the temperature of the rock sample. The present work
pertains to the details of a new Thermal Emission Spectrometer (TES) laboratory that has been developed under the ISRO Planetary
Science and Exploration (PLANEX) programme, for emission related mineralogical investigations of planetary surfaces. The focus
of the paper is on the acquisition and calibration technique for obtaining emissivity, and the deconvolution procedure to
obtain the modal abundances of the thermal emission spectra in the range of 6–25 μm using Fourier Transform Infrared (FTIR)
spectroscopy. The basic technique is adopted from the work of Ruff et al (1997). This laboratory at the Department of Earth Sciences, IIT-Bombay is currently developing pure end mineral library
of mineral particulates (<65 μm), and adding new end members to the existing ASU spectral library. The paper argues the need
for considering Lunar Orbiter Thermal Emission Spectrometer (LOTES) for future Indian Moon mission programme (Chandrayan-II)
to determine evidences of varied lithologies on the lunar surface. 相似文献
17.
Archana Soam 《天文和天体物理学研究(英文版)》2021,(4):79-89
In the work presented here,the impact of magnetic field on the dynamical evolution of cometary globules Sim 129 and Sim 130 in the Sh2-236 HⅡ region and the ionized gas streaming out of their surfaces is investigated.The magnetic field morphology in the region associated with these globules is inferred using optical polarization measurements with the Sampurnanand Telescope at ARIES.The nebular emission is probed through radio continuum mapping at 1.4 GHz with the archival National Radio Astronomy Observatory(NRAO) Very Large Array(VLA) Sky Survey(NVSS) data.The correlation of these measurements suggests that photoevaporated gas from the surfaces of Sim 129 and Sim 130 accumulates in clouds and starts streaming along the magnetic field lines.The ~(12)CO(J=1-0) molecular line observations are performed towards NGC 1893 from the 14-m single dish radio telescope in Taeduk Radio Astronomy Observatory(TRAO).The velocity dispersion in the ~(12)CO(J=1-0) molecular line and the dispersion in polarization angles are considered in the Davis-Chandrasekhar-Fermi formulation to estimate the magnetic field strength towards two Sim nebulae.The average value of field strength is found to be～60 μG with uncertainty of 0.5 times the estimated value. 相似文献
18.
BISHWAKARMA Kiran WANG Guan-xing ZHANG Fan ADHIKARI Subash KARKI Kabita GHIMIRE Archana 《山地科学学报》2022,(2):388-402
The hydrochemical characterization and irrigation suitability assessment of the Ganges-Brahmaputra River System (GBRS) has immense importance for the livelihood... 相似文献
19.
Nachiketa Acharya Ankita Singh U. C. Mohanty Archana Nair Surajit Chattopadhyay 《Natural Hazards》2013,66(2):851-871
The drought during the months of June to September (JJAS) results in significant deficiency in the annual rainfall and affects the hydrological planning, disaster management, and the agriculture sector of India. Advance information on drought characteristics over the space may help in risk assessment over the country. This issue motivated the present study which deals with the prediction of drought during JJAS through standardized precipitation index (SPI) using nine general circulation models (GCM) product. Among these GCMs, three are the atmospheric and six are atmosphere–ocean coupled models. The performance of these GCM’s predicted SPI is examined against the observed SPI for the time period of 1982–2010. After a rigorous analysis, it can be concluded that the skill of prediction by GCM is not satisfactory, whereas the ability of the coupled models is better than the atmospheric models. An attempt has been made to improve the accuracy of predicted SPI using two different multi-model ensemble (MME) schemes, viz., arithmetic mean and weighted mean using singular value decomposition-based multiple linear regressions (SVD-MLR) of GCMs. It is found that among these MME techniques, SVD-MLR-based MME has more skill as compared to simple MME as well as individual GCMs. 相似文献
20.
S. K. Dash Archana Anil Nair Makarand A. Kulkarni U. C. Mohanty 《Theoretical and Applied Climatology》2011,105(3-4):563-570
In this paper, changes in the long and short spells of different rain intensities are statistically analyzed using daily gridded rainfall data prepared by the India Meteorological Department for the period 1951–2008. In order to study regional changes, analyses have been conducted over nine selected agro-meteorological (agro-met) divisions, five homogeneous zones, and also over the whole of India. Rain events of different intensities with continuous rainfall of more than or equal to 4 days are classified here as long spells. Those with less than 4 days are termed as short spells. Those results which are statistically significant at 95% confidence level are discussed in this paper. Trend analysis shows that during the summer monsoon months of June to September, short spell rain events with heavy intensity have increased over India as a whole. On the other hand, long spell rain events with moderate and low intensities have decreased in numbers. Results further show that the contributions of long spell moderate and short spell low-intensity rain events to the total rainfall have decreased whereas the contributions of short spell heavy and moderate-intensity rain events to the total seasonal rainfall have increased. Percentage changes in various categories of long and short spells in the decade 1991–2000 compared with the earlier decade 1951–1960, highlight the maximum increase in heavy-intensity short spell category and decrease in moderate-intensity long spell category in India as a whole and in most of the homogeneous zones and agro-met divisions. The changes in different types of rain events differ in the six homogeneous zones and nine selected agro-met divisions. However, in three homogeneous zones and three agro-met divisions, the short spell heavy-intensity rain events dominate as in the entire country. There are also changes observed in the monthly occurrences of above categories of rain events during the 4 months of summer monsoon. Such results with details of changes in rain categories in different parts of India have important implications in agriculture sector in the country. 相似文献