Current Science

R. Venkatesan ¹

Affiliations
1 National Council of Applied Economic Research (NCAER), Parisila Bhavan, 11, Indraprasta Estate, New Delhi 110 002, IN

Abstract

Sea-water desalination has emerged as the key alternative to overcome demand-supply gap of potable water, worldwide. This paper aims to carry out a technology review of sea-water desalination, technologies in an integrated framework of economic, environmental and ecological analyses. The economic analysis here refers to a project/technology development effort analysis in the context of national economy. The cost per unit output from this perspective is the economic cost. In an environmental analysis, the higher specific energy consumption in a process vis-avis the best technology option in the project area is measured in terms of certified emission reduction. In ecosystem analysis, the accent is to find out whether the technology disrupts the existing eco-system. Such a disturbance entails a huge ecological cost. The cost quantified per unit output is arrived at as the reduction in GDP in the project affected area due to the direct and indirect effects of adverse ecological effects; these effects are deduced using specifically developed I-O tables 'with and without' technology options, for the project area. The choice of technology is the one with the minimum composite cost per unit output. The composite cost in the context is the sum of economic cost, the environmental cost and the ecological cost per unit output. The framework is applied in the technology review of low-temperature thermal desalination process and its impact on project areas of Lakshadweep islands and Thoothukodi district vis-a-vis the alternative RO process of sea-water desalination technology.

Keywords

Economic, Environmental and Ecological Factors, Reverse Osmosis, Sea Water, Thermal Desalination.

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R. Venkatesan ¹, Simi Mathew ¹, J. Vimala ¹, G. Latha ¹, M. Arul Muthiah ¹, S. Ramasundaram ¹, R. Sundar ¹, R. Lavanya ¹, M. A. Atmanand ¹

Affiliations
1 National Institute of Ocean Technology, Velachery–Tambaram Main Road, Pallikaranai P.O., Chennai 600 100, IN

Abstract

The moored buoy network deployed in the Bay of Bengal played a critical role in the collection and transmission of surface meteorological and oceanographic conditions in real time through satellite telemetry, enabling constant monitoring of the cyclone Phailin. It is the first report of in situ timeseries measurement of a very low pressure taken during cyclones in the northern Indian Ocean. The BD10 buoy recorded a minimum atmospheric pressure of 920 hPa, which happened to be within the eye of the cyclone. This article presents an account of important changes that were observed in the surface meteorological and oceanographic parameters under the influence of the very severe cyclonic storm Phailin. An attempt has been made to understand the role of stratification in intensifying the cyclone Phailin in comparison with the cyclone Lehar which weakened in the ocean itself, based on subsurface data from the moored buoys which were on the track of the respective cyclones. Both the cyclones traversed across the Bay of Bengal in a similar way and the buoys were very close to the cyclone track withstood the rough sea conditions during the storms with their specially designed body. The BD09 buoy which happened to be on the right side of the track of cyclone Phailin moved in a circular path as a result of the inertial oscillation forced by the strong cyclonic winds.

Keywords

Cyclonic Storm, Met-Ocean Parameters, Moored Buoy, Real-Time Observations.

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Simi Mathew ¹, Usha Natesan ², G. Latha ¹, R. Venkatesan ¹, Rokkam R. Rao ³, M. Ravichandran ⁴

Affiliations
1 National Institute of Ocean Technology, Pallikaranai P.O., Chennai 600 100, IN
2 Anna University, Guindy Campus, Chennai 600 025, IN
3 International CLIVAR Monsoon Project Office, Indian Institute of Tropical Meteorology, Pashan Road, Pune 411 008, IN
4 National Centre for Antarctic and Ocean Research, Headland Sada, Vasco-da-Gamma, Goa 403 804, IN

Abstract

An unusual near-surface warming was seen in observations from a moored buoy BD11 at 14°N/83°E, and a nearby Argo profiling float in the Bay of Bengal, during the passage of tropical cyclone Thane, during 25–31 December 2011. The cyclone induced a warming of sea surface temperature (SST) by 0.6°C to the right of the track. Heat budget analysis based on moored observations and satellite data rules out the role of horizontal advection and net heat flux in warming the surface layer. We find that vertical mixing/entrainment in response to the cyclone, in conjunction with a pre-storm temperature inversion (subsurface ocean warmer than SST) led to the observed warming. Pre-storm and post-storm salinity and temperature profiles from an Argo float close to the mooring BD11 have higher vertical resolution than the moored data; they suggest vertical mixing of the upper 70 m of the water column. The moored observations show that the thermal inversion, erased by storm-induced mixing, reappears in a few days.

Keywords

Bay of Bengal, Cyclone, OMNI Buoy, SST.

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R. Venkatesan ¹, K. Jossia Joseph ¹, C. Anoopa Prasad ¹, M. Arul Muthiah ¹, S. Ramasundaram ¹, P. Murugesh ¹

Affiliations
1 National Institute of Ocean Technology, Ministry of Earth Sciences, Chennai 600 100, IN

Abstract

The pre-monsoon cyclone Viyaru in the Bay of Bengal during May 2013 traversed a long track from 5°N to 22°N over 7 days with basin-wide response, which was well captured by the time series observations of OMNI buoy network along with satellite data. The differential upper ocean characteristics and its variable response reveal that vertical mixing override horizontal advection during cyclone passage. This study provides insight into the variability in wave spectra, differential response on either side of the track and presence of cold core eddy combined with a thick barrier layer in modulating the upper ocean response.

Keywords

Bay Of Bengal, Barrier Layer, Cyclone Viyaru, Eddies, OMNI Buoys, Wave Spectra.

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Suchandra A. Bhowmick ¹, Neeraj Agarwal ¹, Rashmi Sharma ¹, R. Sundar ², R. Venkatesan ², C. Anoopa Prasad ¹, K. N. Navaneeth ¹

Affiliations
1 Space Applications Centre, Indian Space Research Organization, Ahmedabad 380 015, IN
2 National Institute of Ocean Technology, MOES, Chennai 600 100, IN

Abstract

Amphan, a category-5 tropical cyclone, originated over Bay of Bengal (BoB) and had a landfall in West Bengal, India on 20 May, causing havoc in the region. In this study, in-situ buoy and various satellite measurements are used to analyse the ocean condition before and after the storm, primarily from the air–sea interaction perspective. Widespread anomalous warming was observed in BoB before the event, due to high net surface insolation received by the ocean. The warm SST anomalies in the central BoB were coincident with anti-cyclonic warm core eddies, implying availability of higher oceanic heat content. Observations from BD13 buoy, close to the cyclone track showed heating of the overlying atmosphere due to this ocean warming. Strong surface cooling was observed after passage of the cyclone due to wind induced upper-ocean mixing that is stimulated by low stratification in BoB.

Keywords

Air–Sea Interaction, Oceanic Conditions, Satellite and In situ Observations, Tropical Cyclones.

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