Papers by Ramasamy Venkatesan
IEEE Access
Despite the recent advances in satellite-based L-band microwave radiometry and retrieval algorith... more Despite the recent advances in satellite-based L-band microwave radiometry and retrieval algorithms to provide a unique capability to measure sea surface salinity (SSS) from space and explore its utility for understanding mesoscale dynamics, global ocean circulation, vertical mixing, evaporation rates and climate oscillations, SSS retrieval from L-band microwave radiometric data from the NASA-SMAP (Soil Moisture Active Passive) mission is often biased with systematic errors on larger temporal, spatial scales and random errors on short-time and length scales. To improve the SSS retrieval from SMAP data, we developed a robust algorithm based on a machine-learning approach with high-resolution in-situ data from the Ocean Moored Buoy Network in the Northern Indian Ocean (OMNI), which includes the Arabian Sea (AS) and Bay of Bengal (BoB). The new algorithm was rigorously trained, tested and validated using the in-situ SSS time series measurements from the AS and BoB. Several sensitive variables were examined and used to improve the SSS estimates-such as radiometric and ancillary data from the satellite observations, sea-surface wind and precipitation from the ERA5 data, and SSS/ SST from the OMNI buoy measurements. The OMNI timeseries measurements provided the spatially averaged satellite products to characterize the variability and gross features of SSS in BoB and AS waters on weekly, monthly, seasonal and annual time scales. The systematic validation of SMAP SSS products on a range of spatio-temporal scales showed that the new algorithm improved the SSS estimates by more than 15% in open ocean waters and 25% in river-discharge and precipitation-dominated regions in BoB and AS, when compared to the standard (operational) algorithm. Further analysis demonstrated that the new algorithm reduced clear biases and significant anomalies in SMAP SSS retrievals in the regions of river runoff, surface-freshened ocean and intense tropical cyclones, and captured synoptic/mesoscale SSS features and their seasonal variations in the North Indian Ocean. INDEX TERMS Sea surface salinity, OMNI buoy, SMAP mission, North Indian Ocean, satellite oceanography.
Marine Technology Society Journal, 2021
Precise and accurate monitoring of atmospheric pressure by barometric pressure sensors used in mo... more Precise and accurate monitoring of atmospheric pressure by barometric pressure sensors used in moored buoys in the Indian Ocean is a key factor in cyclone monitoring and climate studies. Underperformance of these sensors has significant impacts on societal protection, weather predictions, and climate modeling. Experimental studies are carried out on the barometric pressure sensors used in moored buoys to quantitatively estimate the uncertainties due to sensor accuracy, drift, static pressure head, and satellite telemetry resolution. The overall measurement uncertainty of the pressure sensors is identified to be ±0.13 hPa, which is within the accuracy limits recommended by the World Meteorological Organization (WMO).
Frontiers in Marine Science, 2020
Whitt et al. Future of Autonomous Ocean Observations reductions. Cost reductions could enable ord... more Whitt et al. Future of Autonomous Ocean Observations reductions. Cost reductions could enable order-of-magnitude increases in platform operations and increase sampling resolution for a given level of investment. Energy harvesting technologies should be integral to the system design, for sensors, platforms, vehicles, and docking stations. Connections are needed between the marine energy and ocean observing communities to coordinate among funding sources, researchers, and end users. Regional teams should work with global organizations such as IOC/GOOS in governance development. International networks such as emerging glider operations (EGO) should also provide a forum for addressing governance. Networks of multiple vehicles can improve operational efficiencies and transform operational patterns. There is a need to develop operational architectures at regional and global scales to provide a backbone for active networking of autonomous platforms.
Estuarine, Coastal and Shelf Science, 2019
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Deep Sea Research Part II: Topical Studies in Oceanography, 2019
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Journal of Physical Oceanography, 2019
Cyclone Phailin, which developed over the Bay of Bengal in October 2013, was one of the strongest... more Cyclone Phailin, which developed over the Bay of Bengal in October 2013, was one of the strongest tropical cyclones to make landfall in India. We study the response of the salinity-stratified north Bay of Bengal to Cyclone Phailin with the help of hourly observations from three open-ocean moorings 200 km from the cyclone track, a mooring close to the cyclone track, daily sea surface salinity (SSS) fromAquarius, and a one-dimensional model. Before the arrival of Phailin, moored observations showed a shallow layer of low-salinity water lying above a deep, warm “barrier” layer. As the winds strengthened, upper-ocean mixing due to enhanced vertical shear of storm-generated currents led to a rapid increase of near-surface salinity. Sea surface temperature (SST) cooled very little, however, because the prestorm subsurface ocean was warm.AquariusSSS increased by 1.5–3 psu over an area of nearly one million square kilometers in the north Bay of Bengal. A one-dimensional model, with initial ...
International Journal on Applied Bio-Engineering, 2007
International Journal on Applied Bio-Engineering, 2009
Aquaculture is now viewed as a strong option to increase fish production as it plays a vital role... more Aquaculture is now viewed as a strong option to increase fish production as it plays a vital role in providing food security in India. Aquaculture informatics can be described as the scientific application of Information technology in biological concepts that enhance the productivity and economic viability of aquaculture sectors. Though there are lot of developments in various aquaculture sectors around the world, Aquaculture in India is still in infancy to use the information from different parts of the country. Advances in electronic communication, combined with specific cooperative efforts, should be used to increase the information exchange in the region. It is nation's part to educate the fish farmers through community based organization and to provide an information system, in low cost, to fulfill their requirements. In order to develop a single hub for the integrated activity, some community based organizations are formed like fish farmers association, self help group or aqua club. This paper is on the integration of aquaculture information based tools under one hub to design to work through a community based system.
Springer Series on Biofilms
... In addition, mussels are constrained to close their shell valves in response to continuous ch... more ... In addition, mussels are constrained to close their shell valves in response to continuous chlo-rination. However, studies by Rajagopal et al. (2003) have shown the method to Page 12. 276 R. Venkatesan and PS Murthy be ...
2015 IEEE Underwater Technology (UT), 2015
Moored Buoy Systems are one of the most common platforms of Ocean Observations for cost- effectiv... more Moored Buoy Systems are one of the most common platforms of Ocean Observations for cost- effective means of obtaining meteorological and oceanographic data. In addition to these, several other modes of unmanned systems have been evolved in the past decades for long term observations such as Autonomous Underwater Vehicles (AUVs), Autonomous Underwater Gliders (AUGs). Thus, as a part of development strategy for new tools to have long term ocean observations with minimum energy consumption, developments are undertaken at OOS, NIOT. This paper presents the preliminary design methodology of one such development being pursued at NIOT i.e. a Laboratory Scale Underwater Glider (LSUG) and a small robotic underwater vehicle which mimics a fish called AquaBot.
New Zealand Journal of Marine and Freshwater Research, 2005
A pair of subadult Panulirus ornatus was reared in the laboratory from July 2001. The female grew... more A pair of subadult Panulirus ornatus was reared in the laboratory from July 2001. The female grew from 0.6 to 1.3 kg and the male from 0.5 to 1.6 kg in 2 years before the first mating in July 2003. In 6 months, from July to December 2003, the pair mated and spawned 3 times, producing 1.6 million eggs and 1.1 million phyllosoma larvae. Mating occurred 25 and 63 days after moulting. The female spawned 2-3 days after mating and the incubation time ranged from 23 to 27 days. The phyllosoma larvae were released over 2 successive days. The growth rate reduced after first mating in both the male and female and the female expended 42% of the total weight gain for egg production.
Frontiers in Marine Science, 2021
The UN Decade of Ocean Science for Sustainable Development (Ocean Decade) challenges marine scien... more The UN Decade of Ocean Science for Sustainable Development (Ocean Decade) challenges marine science to better inform and stimulate social and economic development while conserving marine ecosystems. To achieve these objectives, we must make our diverse methodologies more comparable and interoperable, expanding global participation and foster capacity development in ocean science through a new and coherent approach to best practice development. We present perspectives on this issue gleaned from the ongoing development of the UNESCO Intergovernmental Oceanographic Commission (IOC) Ocean Best Practices System (OBPS). The OBPS is collaborating with individuals and programs around the world to transform the way ocean methodologies are managed, in strong alignment with the outcomes envisioned for the Ocean Decade. However, significant challenges remain, including: (1) the haphazard management of methodologies across their lifecycle, (2) the ambiguous endorsement of what is “best” and when...
Marine Geodesy, 2013
This article may be used for research, teaching, and private study purposes. Any substantial or s... more This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae, and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand, or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material.
Colloids and Surfaces B: Biointerfaces, 2008
What proteins are made from, as the working parts of the living cells protein machines? To answer... more What proteins are made from, as the working parts of the living cells protein machines? To answer this question, we need a technology to disassemble proteins onto elementary functional details and to prepare lumped description of such details. This lumped description might have a multiple material realization (in amino acids). Our hypothesis is that informational approach to this problem is possible. We propose a way of hierarchical classification that makes the primary structure of protein maximally non-random. The first step of the suggested research program is realized: the analysis of protein binary alphabet in comparison with other amino acid classifications.
2013 Ocean Electronics (SYMPOL), 2013
ABSTRACT The moored buoy network maintained by NIOT has crucial role in cyclone and Tsunami warni... more ABSTRACT The moored buoy network maintained by NIOT has crucial role in cyclone and Tsunami warning. It is significant to have continuous, reliable real time data from these moored buoy systems. This paper explains the evolution of effective power system attained after years of experience and extensive study of buoy power system. Non-rechargeable lithium batteries are being used as primary power source because the buoy systems with Lead Acid batteries charged by solar panels are prone to damage. Later a dual battery system was implemented wherein lead acid battery would power the buoy system and in case of failure, the primary lithium battery can take over. A study is being made on installation of wind turbine on the buoy system to cater the power required for redundant charging mechanism.
a b s t r a c t In the wake of adoption of the resolution by the International Maritime Organizat... more a b s t r a c t In the wake of adoption of the resolution by the International Maritime Organization to control biofouling on vessels, which is recognized as a major vector for transfer of invasive species, this study attempts to create a baseline data on major hard-shelled biofouling organisms in the harbour waters. This study was primarily focused towards understanding the biofouling and corrosion pattern on various metals and their performance under immersed condition in a marine environment, at 0.3 and 3.0 m depths. Furthermore, the study attempts to understand the surface dependent characteristics of barnacle base plate and its adhesion strength. Barnacle, mussels and oysters were the major fouling organisms accounting for 72.33% of the variation. Stainless steel and Titanium panels showed the highest average biofouling load of 176.36 and 168.35 g/300 cm 2 , respectively. The variance in biofouling between metals and depths was highly significant at p < 0.001 and p < 0.01...
This chapter focuses on recent progress and emerging directions in ocean observations. The import... more This chapter focuses on recent progress and emerging directions in ocean observations. The importance of sustained observations and status of the global ocean observing network are covered. Emerging trends include many exciting developments, such as Bio-ARGO floats, autonomous or remotely-operated instruments and platforms, and new measurement capabilities focused on fundamental ocean processes. Numerical models that integrate and assimilate multi-scale observations of the atmosphere, land, ice and ocean will lead to new science as well as improved forecasts of great societal value.
Lobsters are one of the highly esteemed seafood delicacies and cu r re n t ly fetch the highest u... more Lobsters are one of the highly esteemed seafood delicacies and cu r re n t ly fetch the highest unit value among commercially exploited marine resources. These are decapod crustaceans belonging to fo u r fami l ie s : Nephropidae {clawed / true lobsters), Palinuridae {Spiny/ rock lobsters), Scyllaridae (Sand /slipper lobsters) and Synaxidae (Coral lobsters). Representatives of the families Palinuridae and Scyllaridae constitute the lobster fisher000y of India.
Prediction of significant wave heights (Hs) is of immense importance in ocean and coastal enginee... more Prediction of significant wave heights (Hs) is of immense importance in ocean and coastal engineering applications. The aim of this study is to predict significant wave height values at buoy locations with the lead time of 3,6,12 and 24 hours using past observations of wind and wave parameters applying Artificial Neural Network. Although there exists a number of wave height estimation models, they do not consider all causative factors without any approximation and consequently their results are more or less a general approximation of the overall dynamic behaviour. Since soft computing techniques are totally data driven, based on the duration of the data availability they can be used for prediction. In the National data buoy program of National institute of Ocean Technology, not all the buoys have wind sensors and wave sensors and so it is attempted to apply neural network algorithms for prediction of wave heights using wind speed only as the input and then using only wave height as ...
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Papers by Ramasamy Venkatesan