http://nopr.niscair.res.in/handle/123456789/1499 Search the Channel search http://nopr.niscair.res.in/simple-search http://nopr.niscair.res.in/handle/123456789/1580 Title: Coastal processes along the Indian coast - Case studies based on synergistic use of IRS-P4 OCM and IRS-1C/1D data <br/> <br/>Authors: Rajawat, A.S.; Gupta, Mukesh; Pradhan, Yaswant; Thomaskutty, A.V.; Nayak, Shailesh <br/> <br/>Abstract: The sequential Suspended Sediment Concentration (SSC) maps were generated using IRS-P4 OCM (Ocean Color Monitor) data for selected tide dominated, wave dominated and deltaic coasts around the Indian subcontinent. Patterns of SSC were studied to understand the sediment dynamics, circulation patterns, fronts and consequent impact on coastal processes. Hitherto, unknown sediment plumes extending for large distance into deep offshore areas could be identified from the major deltaic regions. The high temporal capability of OCM data was extremely useful to understand sediment dynamics in tide-dominated regions of the Gulf of Khambhat, the Gulf of Kachchh and the Hoogli estuary. SSC maps in conjunction with corresponding tide and bathymetry data could be sequenced as per flooding and ebb cycles. Development, formation, shifting nature of shoals and sediment curls during a tide cycle could be studied. It is observed that during the North-East (NE) monsoon suspended sediment influx of the Ganga-Brahmaputra system influences the coastal processes along the continental margins of the Orissa and the Northern Andhra Pradesh along east coast of India. The occurrence of cyclone aids in entrapment of fluvial discharge into the coastal waters, leading to a reduced offshore influx into deeper regions of the Bay of Bengal and high sedimentation near to the coast. Seasonal changes along wave-dominated west coast showed net sediment transport from north to south in the pre-monsoon season and south to north in post-monsoon season. Significant onshore- offshore transport along west coast was also observed. The impact of the regional sediment dynamics on the site-specific local coastal environment was studied by integrating observations derived from OCM and IRS-1C/1D data. The paper concludes the utility of Ocean Color Monitor and IRS-1C/1D data in studying various coastal processes and regional sediment dynamics. <br/> <br/>Page(s): 459-472 http://nopr.niscair.res.in/handle/123456789/1579 Title: A persistent eddy in the central Arabian Sea: Potential trophic significance <br/> <br/>Authors: Kumari, Beena; Mass, H.; Panigrahy, R. C.; Navalgund, R. R. <br/> <br/>Abstract: Arabian Sea is an area of strong currents, complicated flow patterns with several eddies and semi annually reversing monsoon winds. This paper deals with a cold eddy highly rich in phytoplankton in the Central Arabian Sea, centered around: 14º 25’ N and 69º 20’ E during January – March 1998. The eddy was about 100 km in diameter with a depth of about 4000 m and maximum chlorophyll-a concentration was 1 mg m⁻³ compared with 0.2 mg m⁻³ in the surrounding areas. Average optical depth of the area was 12 m. The occurrence of the eddy and the related oceanographic variables were inferred from SeaWiFS derived chlorophyll-a (Chl-a), NOAA Pathfinder AVHRR derived sea surface temperature, sea surface height from TOPEX altimeter and collateral information. The cold eddy formation is probably due to longshore density variation in the ocean. Due to negative sea level anomalies, associated surface divergence and upwelling process, the region of cold eddy is known to be highly productive. The cold eddy in the same location was observed during January 2000. The persistence of the eddy for more then a month indicates that this area is a rich forage ground for tuna fishery. <br/> <br/>Page(s): 449-458 http://nopr.niscair.res.in/handle/123456789/1578 Title: Application of QuikSCAT SeaWinds data to improve remotely sensed Potential Fishing Zones (PFZs) forecast methodology: Preliminary validation results <br/> <br/>Authors: Solanki, H.U.; Pradhan, Yashwant; Dwivedi, R.M.; Nayak, Shailesh <br/> <br/>Abstract: In this study, we used chlorophyll concentration and sea surface temperature (SST) images derived from IRS P4-OCM and NOAA- AVHRR, respectively, to delineate the oceanographic features exhibiting different oceanic processes. QuikSCAT-SeaWinds derived wind vectors were used to understand, establish, quantify and to demonstrate the variability of wind induced watermass flow as well as their impacts on features/oceanographic process. Oceanographic features like eddies, rings and fronts were found shifted as per movement and direction of the wind. The movement of water mass due to wind provides insight of environmental factors relevant to dispersal of fishery resources. An algorithm was developed to compute water mass transport and feature shift. Based on these studies an approach for incorporating QuikSCAT-SeaWinds data to improve PFZs forecast methodology has been developed. The improved PFZs forecast methodology was validated through near real time fishing operations. About 82-85% success rate was reported during validation experiments carried out during 2004. The improved methodology would prolong the validity of PFZs forecast. <br/> <br/>Page(s): 441-448 http://nopr.niscair.res.in/handle/123456789/1577 Title: Exploration of fishery resources through integration of ocean colour with sea surface temperature: Indian experience <br/> <br/>Authors: Dwivedi, R.M.; Solanki, H.U.; Nayak, S.R.; Gulati, D.; Somvanshi, V.S. <br/> <br/>Abstract: Exploration of fishery resources using remote sensing technique is based on the principle of identification of feeding grounds where fish tend to accumulate. It has been proven that thermal or colour gradients revealed by oceanic fronts indicate sites of high biological productivity. Some constraints in using SST (sea surface temperature) gradients for locating fish in the Indian waters were experienced such as the narrow range of SST and difficulty in detecting gradients, particularly in summer. Two approaches were developed and validated in the coastal waters of the west coast of India. In the first approach, SST contours (using NOAA AVHRR) were overlaid on chlorophyll image (from IRS P4 OCM) of corresponding date. This enabled identification of common frontal structures from the composite product. These sites were selected as priority fishing zones for the trial forecasts. Besides, ocean colour images were found to provide information on additional productive areas not found from SST images alone and hence, a second approach made exclusive use of patterns of ocean colour. Merits of ocean colour arose from penetration of visible radiation below surface up to one attenuation depth and from the frequent repeat cycle of the satellite data. The improvements with use of ocean colour include capability of prediction of oceanic features, exploitation of knowledge of the history of the features, identification of biological fronts in the deep sea waters etc. Also, such features as non-toxic winter blooms and internal waves were identified in the deep waters of the Northern Arabian Sea using chlorophyll images and the response of fish to these features was studied. This paper highlights how ocean colour improves our ability to locate areas of high abundance of fish. Because the time taken in information extraction from satellite data is a critical factor, on-line reception of OCM and AVHRR data was arranged. Fishery forecasts were generated using the integrated approach within 24 hours of satellite over pass, and disseminated to collaborating agencies for follow up fishing operation. The validation experiment for the forecasts was carried out for three years covering different seasons during 1999-2001. It was found that the forecasts were superior in terms of rate of success and magnitude of fish catch. Summary of feedback received indicated 70-90 % success rate (reliability) of the forecasts and 70-200 % increase in catch. In comparison with this, earlier SST-based approaches for the forecast yielded 50 % success rate and 40-50 % increase in catch. The integrated approach is currently being used to generate nation-wide fishery forecasts. In addition to this, cost-benefit analysis for the satellite fishery forecasts was also attempted. It was observed that the benefit:cost ratio increased from 1.27 to 2.12 for bottom trawling and 1.3 to 2.14 for gillnet fishing with the use of satellite forecasts. <br/> <br/>Page(s): 430-440