Response of infaunal macrobenthos to the sediment granulometry in a tropical continental margin–southwest coast of India     

K.A. Jayaraj  P. Sheeba  Josia Jacob  C. Revichandran  P.K. Arun  K.S. Praseeda  P.A. Nisha  K.A. Rasheed 《Estuarine, Coastal and Shelf Science》2008,77(4):743-754

Surficial sediment samples, collected from the continental margin of the southwest coast of India in July 2004, were examined for the grain size and soft-bottom macrobenthic fauna, to understand the sediment granulometry and its effect on the faunal distribution. Samples were collected using Smith-McIntyre Grab, from 20 to 200 m depth range, consisting of mid-shelf, outer shelf and slope. Fine-grained sediment located in the mid shelf and supported low faunal abundance. Polychaetes constituted the bulk of the fauna. Feeding guild changed with depth and sediment granulometry. Coexistence of deposit feeders and carnivores in outer shelf and deposit feeders and filter feeders in the slope region indicated the effective utilization of different food resources. In general, richness and diversity were high in the southern region. Depth wise, the diversity and abundance were relatively high in the 50–75 m depth range. Correlation and BIO-ENV analysis showed that combination of different factors such as sediment texture, sediment sorting and depth were found to influence the distribution of macrobenthos. Hence, spatial variations observed in benthic community were presumably linked to the variations in sediment granulometry and the energy level conditions prevailing in the area.  相似文献   

Evaluation of the CFSv2 CMIP5 decadal predictions     

Rodrigo J. Bombardi  Jieshun Zhu  Lawrence Marx  Bohua Huang  Hua Chen  Jian Lu  Lakshmi Krishnamurthy  V. Krishnamurthy  Ioana Colfescu  James L. Kinter III  Arun Kumar  Zeng-Zhen Hu  Shrinivas Moorthi  Patrick Tripp  Xingren Wu  Edwin K. Schneider 《Climate Dynamics》2015,44(1-2):543-557

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On the potential of extratropical SST anomalies for improving climate predictions     

Arun Kumar  Hui Wang 《Climate Dynamics》2015,44(9-10):2557-2569

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Flood monitoring using microwave remote sensing in a part of Nuna river basin,Odisha, India     

Sananda Kundu  S. P. Aggarwal  Nanette Kingma  Arun Mondal  Deepak Khare 《Natural Hazards》2015,76(1):123-138

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Establishment of lightning detection sensors network in India: generation of essential climate variable and characterization of cloud-to-ground lightning occurrences     

Taori  Alok  Suryavanshi  Arun  Pawar  Sunil  Seshasai  M. V. R. 《Natural Hazards》2022,111(1):19-32

Natural Hazards - A network of 25 lightning detection sensors (LDS) has been established by the National Remote Sensing Centre (NRSC), the Indian Space Research Organization (ISRO). At present,...  相似文献   

Chemical characterization of wet precipitation events and deposition of pollutants in coal mining region,India     

Abhay Kumar Singh  G. C. Mondal 《Journal of Atmospheric Chemistry》2008,59(1):1-23

The present study investigated the chemical composition of wet atmospheric precipitation in India’s richest coal mining belt. Total 418 samples were collected on event basis at six sites from July to October in 2003 and May to October in 2004 and analysed for pH, EC, F⁻, Cl⁻, , , Ca²⁺, Mg²⁺, Na⁺, K⁺ and . The average pH value (5.7) of the rainwater of the investigated area is alkaline in nature. However, the temporal pH variation showed the alkaline nature during the early phase of monsoonal rainfall but it trends towards acidic during the late and high rainfall periods. The rainwater chemistry of the region showed high contribution of Ca²⁺ (47%) and (21%) in cations and (55%) and Cl⁻ (23%) in anionic abundance. The high non seas salt fraction (nss) of Ca²⁺ (99%) and Mg²⁺ (96%) suggests crustal source of the ions, while the high nss (96%) and high ratio signifying the impact of anthropogenic sources and the source of the acidity. The ratio of varies from 0.03 to 3.23 with the average value of 0.84 suggesting that Ca²⁺ and play a major role in neutralization processes. The assessment of the wet ionic deposition rates shows no any specific trend, however Ca²⁺ deposition rate was highest followed by and _.  相似文献   

Prediction of summer monsoon rainfall over India using the NCEP climate forecast system   总被引：1，自引：0，他引：1  

D. R. Pattanaik  Arun Kumar 《Climate Dynamics》2010,34(4):557-572

The performance of a dynamical seasonal forecast system is evaluated for the prediction of summer monsoon rainfall over the Indian region during June to September (JJAS). The evaluation is based on the National Centre for Environmental Prediction’s (NCEP) climate forecast system (CFS) initialized during March, April and May and integrated for a period of 9 months with a 15 ensemble members for 25 years period from 1981 to 2005. The CFS’s hindcast climatology during JJAS of March (lag-3), April (lag-2) and May (lag-1) initial conditions show mostly an identical pattern of rainfall similar to that of verification climatology with the rainfall maxima (one over the west-coast of India and the other over the head Bay of Bengal region) well simulated. The pattern correlation between verification and forecast climatology over the global tropics and Indian monsoon region (IMR) bounded by 50°E–110°E and 10°S–35°N shows significant correlation coefficient (CCs). The skill of simulation of broad scale monsoon circulation index (Webster and Yang; WY index) is quite good in the CFS with highly significant CC between the observed and predicted by the CFS from the March, April and May forecasts. High skill in forecasting El Nino event is also noted for the CFS March, April and May initial conditions, whereas, the skill of the simulation of Indian Ocean Dipole is poor and is basically due to the poor skill of prediction of sea surface temperature (SST) anomalies over the eastern equatorial Indian Ocean. Over the IMR the skill of monsoon rainfall forecast during JJAS as measured by the spatial Anomaly CC between forecast rainfall anomaly and the observed rainfall anomaly during 1991, 1994, 1997 and 1998 is high (almost of the order of 0.6), whereas, during the year 1982, 1984, 1985, 1987 and 1989 the ACC is only around 0.3. By using lower and upper tropospheric forecast winds during JJAS over the regions of significant CCs as predictors for the All India Summer Monsoon Rainfall (AISMR; only the land stations of India during JJAS), the predicted mean AISMR with March, April and May initial conditions is found to be well correlated with actual AISMR and is found to provide skillful prediction. Thus, the calibrated CFS forecast could be used as a better tool for the real time prediction of AISMR.  相似文献   

“Shock event”, an impact phenomenon observed in water wells around the Arabian Gulf coastal city Dammam,Saudi Arabia: possible relationship with Sumatra tsunami event of December 26, 2004     

Arun Kumar  Syed A. Alam 《Natural Hazards》2010,53(2):407-412

A sudden disturbance in water level was recorded by hydrographs monitoring wells in the coastal city Dammam, Saudi Arabia on December 26, 2004. The water level was being recorded from the shallow (1–3 M deep) coastal aquifer at that time. In two wells, this disturbance was observed ~12 h after the Sumatra earthquake/tsunami event of December 26, 2004. The timing of this event is synchronous in two wells near the coast, but an inland well away from the coast line did not show any such disturbance. It is hypothesized that this disturbance, we call it the “shock event”, is resulted by sudden impact of tsunamis traveling in the Arabian Gulf from southeast toward northwest. As the tsunamis propagated, they suddenly impacted the coastal shallow groundwater aquifer resulting in the “shock event”.  相似文献   

Compositional variations in the Mesoarchean chromites of the Nuggihalli schist belt, Western Dharwar Craton (India): potential parental melts and implications for tectonic setting     

Ria Mukherjee  Sisir K. Mondal  Minik T. Rosing  Robert Frei 《Contributions to Mineralogy and Petrology》2010,160(6):865-885

The chromite deposits in the Archean Nuggihalli schist belt are part of a layered ultramafic–mafic sequence within the Western Dharwar Craton of the Indian shield. The 3.1-Ga ultramafic–mafic units occur as sill-like intrusions within the volcano-sedimentary sequences of the Nuggihalli greenstone belt that are surrounded by the tonalite–trondhjemite–granodiorite (TTG) suite of rocks. The entire succession is exposed in the Tagdur mining district. The succession has been divided into the lower and the upper ultramafic units, separated by a middle gabbro unit. The ultramafic units comprise of deformed massive chromitite bodies that are hosted within chromite-bearing serpentinites. The chromitite bodies occur in the form of pods and elongated lenses (~60–500 m by ~15 m). Detailed electron microprobe studies reveal intense compositional variability of the chromite grains in silicate-rich chromitite (~50% modal chromite) and serpentinite (~2% modal chromite) throughout the entire ultramafic sequence. However, the primary composition of chromite is preserved in the massive chromitites (~60–75% modal chromite) from the Byrapur and the Bhaktarhalli mining district of the Nuggihalli schist belt. These are characterized by high Cr-ratios (Cr/(Cr + Al) = 0.78–0.86) and moderate Mg-ratios (Mg/(Mg + Fe²⁺) = 0.38–0.58). The compositional variability occurs due to sub-solidus re-equilibration in the accessory chromite in the serpentinite (Mg-ratio = 0.01–0.38; Cr-ratio = 0.02–0.99) and in silicate-rich chromitite (Mg-ratio = 0.06–0.48; Cr-ratio = 0.60–0.99). In the massive chromitites, the sub-solidus re-equilibration for chromite is less or absent. However, the re-equilibration is prominent in the co-existing interstitial and included olivine (Fo_96–98) and pyroxene grains (Mg-numbers = 97–99). Compositional variability on the scale of a single chromite grain occurs in the form of zoning, and it is common in the accessory chromite grains in serpentinite and in the altered grains in chromitite. In the zoned grains, the composition of the core is modified and the rim is ferritchromit. In general, ferritchromit occurs as irregular patches along the grain boundaries and fractures of the zoned grains. In this case, ferritchromit formation is not very extensive. This indicates a secondary low temperature hydrothermal origin of ferritchromit during serpentinization. In some occurrences, the ferritchromit rim is very well developed, and only a small relict core appears to remain in the chromite grain. However, complete alteration of the chromite grains to ferritchromit without any remnant core is also present. The regular, well-developed and continuous occurrence of ferritchromit rims around the chromite grain boundaries, the complete alteration of the chromite grains and the modification of the core composition indicate the alteration in the Nuggihalli schist belt to be intense, pervasive and affected by later low-grade metamorphism. The primary composition of chromite has been used to compute the nature of the parental melt. The parental melt calculations indicate derivation from a high-Mg komatiitic basalt that is similar to the composition of the komatiitic rocks reported from the greenstone sequences of the Western Dharwar Craton. Tectonic discrimination diagrams using the primary composition of chromites indicate a supra-subduction zone setting (SSZ) for the Archean chromitites of Nuggihalli and derivation from a boninitic magma. The composition of the komatiitic basalts resembles those of boninites that occur in subduction zones and back-arc rift settings. Formation of the massive chromitites in Nuggihalli may be due to magma mixing process involving hydrous high-Mg magmas or may be related to intrusions of chromite crystal laden magma; however, there is little scope to test these models because the host rocks are highly altered, serpentinized and deformed. The present configurations of the chromitite bodies are related to the multistage deformation processes that are common in Archean greenstone belts.  相似文献   

A simple approach for improving spatial interpolation of rainfall using ANN     

C. Sivapragasam  V. M. Arun  D. Giridhar 《Meteorology and Atmospheric Physics》2010,107(1-2):1-7

The spatiotemporal features of tropical cyclone strikes from 1949 to 2008 at 49 coastal cities of China are investigated in this study. The cities in Hainan, Guangdong, and Taiwan have high strike frequencies, with the severest and most frequent average strikes found in Taiwan. In Hainan, strike clusters appear in the mid-1950s, the early 1960s and 1970s, and the late 1980s, with relative inactive frequencies from the mid-1990s to 2008, and the clusters of strikes in Guangdong are found during the 1970s. In Taiwan, the most active strikes are found during the period 1956–1963. The return periods for all typhoons are either 1 or 2 years at the coastal cities of Taiwan in contrast to 2–5 and 4–8 years at the cities of Guangdong and Fujian, respectively. Super typhoons affect Taiwan with a frequency of once every 12–30 years on average. A tropical cyclone hazard index is also created to investigate the vulnerability at these cities.  相似文献