T.M. Balakrishnan Nair

Indian National Centre for Ocean Information Services | INCOIS · Information Services and Ocean Science Group

This study investigates the impact of Cyclone Michaung on coastal dynamics and biological changes in the southeastern Arabian Sea (SEAS). Utilizing data from a moored autonomous buoy, the water quality nowcasting system (WQNS), and multi-satellite datasets, the research documents significant changes in sea surface temperature (SST), salinity, and d...

This study investigates the impact of Cyclone Michaung on coastal dynamics and biological changes in the southeastern Arabian Sea (SEAS). Utilizing data from a moored autonomous buoy, the water quality nowcasting system (WQNS), and multi-satellite datasets, the research documents significant changes in sea surface temperature (SST), salinity, and d...

The Coupled Model Intercomparison Project phase Six (CMIP6) lacks wave climate projections, emphasising the critical need to select the most accurate CMIP6 model winds for projecting wave climate. This study focuses on evaluating and selecting the optimal CMIP6 model wind fields for the Indian Ocean wave climate projections. A 35‐year (1980–2014) w...

The Indian oil sardine (Sardinella longiceps, hereafter IOS) has a unique position in terms of its economic value. In the last decade, IOS has contributed about 15–20% to India's total marine fish landings. However, recently, a sharp decline has been observed in the annual landing of the resource, and it is on the verge of collapsing due to climati...

Marine litter in the Bay of Bengal has been under-studied despite large quantities of mismanaged waste reportedly entering the ocean from its surrounding countries. The seasonal reversal of monsoon currents in this region provides a unique environment for the transport of floating macro-litter. A particle tracking model is used here to investigate...

This study delves into the research conducted and the challenges faced in recent decades, with the evolution of monitoring techniques from traditional in-situ methods to cutting-edge remote sensing technologies. It further explores the immense potential of remote sensing and machine learning advancements to enhance our capabilities for monitoring a...

Uninterrupted communication during pre-disaster preparedness and post-disaster recovery greatly reduces mortality. Unfortunately, during natural calamities, communication becomes void as terrestrial communication infrastructure is destroyed and becomes non-functional. In this study, we unveil the innovative use of available message slots, previousl...

Indian Mackerel (Rastrelliger kanagurta) is an essential small pelagic fishery resource, contributing to nearly 30 % of India's total marine fish landing. However, this species' life cycle and stock status are poorly understood and data deficient. Ocean mesoscale events are also known to influence their landing, besides the environmental factors li...

The paper presents the development of a high-resolution mesoscale atmospheric numerical model Advanced Research WRF (ARW 3.7, henceforth ARW)-based operational forecast system, and evaluation of its surface wind forecasts using buoys and satellite data in the Indian Ocean. This was set up as part of the ocean state forecasting system to force the o...

The southwest coast of India experiences frequent Indian oil sardine (IOS) nearshore aggregation events, especially in the coastal waters off Kerala. These ephemeral dense IOS aggregation events are known as “Sardine Run”. To investigate the reason and provide a scientific basis for these sporadic events, satellite/model-derived physical, meteorolo...

Sustained advancements in the developed ocean wave models are of paramount importance to get realistic simulations of the ocean wind waves. In the present study, a novel technique viz., 'Boundary Condition Impartation Technique' (BCIT) has been developed and implemented to directly nest an unstructured mesh version of the coastal wave model Simulat...

The Indian National Centre for Ocean Information Services (INCOIS) developed Search and Rescue Aid Tool (SARAT) to aid the Indian Search and Rescue (SAR) agencies in their operations at sea. The SARAT application can simulate the probable search area of a range of objects lost at sea, when provided with the last known time and location of the lost...

Existing services and Research towards advisory services in operational oceanography

Trawling is a major fishing method used in marine fisheries around the world, including in India. In India, more than 50% of marine fish landings come from the trawl fishing system. In recent years, there has been a steady rise of jellyfish blooms in estuarine and coastal waters of India. It is well known that jellyfish impact commercial fisheries...

This study examined the factors controlling the intra- and inter-seasonal variations of dissolved methane (CH4) and nitrous oxide (N2O) in the southeastern Arabian Sea (SEAS). Time-series measurements of CH4, N2O and allied biogeochemical parameters were carried out during the monthly campaigns in the coastal waters and a seasonal campaign in the s...

Interannual climate modes, especially the southern annular mode (SAM), significantly influence the wave climate modulation of the Indian Ocean (IO). The present study, aligned with previous research, identifies two crucial swell generation regions in the IO: the extratropical southern Indian Ocean (ETSI) and the tropical southern Indian Ocean (TSIO...

Climate change is a global phenomenon that has enhanced sea-level rise and aggravated the prevailing coastal hazards that make coasts more vulnerable. The socioeconomic vulnerability of villages for the entire Andhra Pradesh state and buildings at the selected locations along the Andhra Pradesh coast is estimated to understand the level of risk due...

This paper is about the influence of environmental and oceanographic parameters in the Malabar Upwelling Region on the availability of Indian Mackerel from 1985-2012.

Fish mass mortality and jellyfish beach stranding were observed before the landfall of tropical cyclone Yaas, in the nearshore waters of Puri, a major tourist destination along the eastern seaboard of India. This very severe cyclonic storm crossed the northern coast of Odisha, near Balasore, on 26th May 2021, and Puri was near the vicinity of the c...

This study assesses the performance of different source term packages of WAVEWATCH III (WWIII, V-6.07) wave model for various wave conditions in the Indian Ocean (IO). Eight simulations of WWIII were made for the year 2017, four using default source term packages (ST2, ST3, ST4, and ST6) and another four by tuning the wind–wave interaction paramete...

Rip currents are one of the most well-known coastal hazards on the world's beaches. Identification and continuous monitoring of these currents are essential for the safety of beachgoers and prevent the number of drowning cases. Studies on the diversity of rip currents in space and time off the Indian coast are minimal. However, these have long been...

The south-western coast of India recently witnessed an intense bloom of green Noctiluca scintillans (NS) that resulted in water discolouration, scummy surface layer, bioluminescent tides, and mass fish mortality. The Algal Bloom Information Service (ABIS) of the Indian National Centre for Ocean Information Services could efficiently provide informa...

The present study highlights the wave–tide interactions in a tide-dominant coast Versova, along the west coast of India. Versova is a macro tidal area and is home to fisheries. Model simulations are carried out to investigate wave–tide interactions with and without incorporating water level (WL) variations in the model setup. The simulation results...

In this study, long-term hourly sea-level records from 18 tide gauge stations during 1972–2007 were analyzed to study the characteristics of astronomical tides, sea-level trends, and extremes around India's mainland. The de-tided signals were used to estimate these parameters and study tide and surge interaction. The observed sea level depicts sign...

India has a vast coastline of ~7,500 km encompassing the west coast (eastern Arabian Sea), east coast (western Bay of Bengal), and islands. The coastal water of India is rich in a wide variety of marine biotic and abiotic resources that support the livelihood of millions through fishery, recreational activities, tourism, marine commerce, maritime l...

India is adept in implementing the latest technological advancements and research findings with its fully operational ocean information and advisory services for the Indian Ocean. The operational services viz. Ocean State Forecast (OSF) and Marine Fishery Advisory Services (MFAS) support not only the stakeholders in India, but also those in other n...

The Indian National Centre for Ocean Information Services (INCOIS) developed Search And Rescue Aid Tool (SARAT) to aid the Indian authorities involved in Search And Rescue (SAR) operations at sea. The SARAT application can simulate the probable trajectory of a range of objects lost at sea, when provided with the information of time and location of...

Indian Coast Guard and oil spill responders utilise the operational oil spill advisory services of the Indian National Centre for Ocean Information Services (INCOIS) during the event of oil spills for setting up spill response operations. Oil drifts in marine zones are dominated by ocean currents. Ocean currents generated by numerical models have e...

The coastal flood during the tropical cyclone Tauktae, 2021, at Chellanam coast, Kerala, India, has invited wide attention as the wave overtopping severely affected coastal properties and livelihood. We used a combination of WAVEWATCHIII and XBeach to study the coastal inundation during high waves. The effect of low-frequency waves and the rise in...

Extreme ocean surface waves can significantly impact the coastal and offshore-related activities, and often cause large-scale destruction to the livelihoods of the coastal population. To potentially reduce the adverse societal impacts and planning operations, it is necessary to assess the futuristic changes in extreme wave climate. This study exami...

Identifying coastal stretches that are likely to erode under high wave conditions is essential to the coastal management community in addressing beach erosion-related issues. The manuscript presents a case study to predict erosion of a selected beach located on the eastern Indian coast during the 2018 southwest (SW) monsoon season. The pre-monsoon...

Unexpected occurrences of freak waves endanger safe navigation and operational activities in the ocean. To reduce the potential marine accidents, many oceanographers have investigated the probability and mechanism of freak wave occurrences and discussed some relevant environmental factors leading to freak wave generations. However, study on the occ...

Phytoplankton blooms are frequent in the coastal waters of the northwestern Bay of Bengal (BoB), with diatom blooms being the most common. For the first time, this study investigated the long-term trend in ocean color satellite-retrieved diatom distribution in coastal waters of the northwestern BoB. A retrospective analogy of phytoplankton bloom ev...

The coastal flood during the Tauktae cyclone, 2021, at Chellanam coast, Kerala, India, has invited wide attention as the wave overtopping severely affected coastal properties and livelihood. We used a combination of WAVEWATCHIII and XBeach to study the coastal inundation during high waves. The effect of low-frequency waves and rise in the coastal w...

The present study analyzes the impact of the Southern Ocean (SO) sea ice concentration on the north Indian Ocean (NIO) wave fields through swells using 6 years (2016–2021) of WAVEWATCH III (WWIII) simulations. We did two experimental runs of WWIII, one with sea ice concentration and winds as the forcing (W3with_ice) and the second run with only win...

Tropical Cyclone Ockhi was an intense cyclone, with a peculiar and long track, in the Arabian Sea in 2017. It caused severe damage to coastal infrastructure and death of 282 people. Indian National Centre for Ocean Information Services (INCOIS) issued the Joint INCOIS-IMD (India Meteorological Department) bulletins on the Ocean State Forecasts (OSF...

Rip currents are one of the most well-known coastal hazards on the world’s beaches. Identification and continuous monitoring of these currents are essential for the safety of beachgoers and prevent the number of drowning cases. Studies on the diversity of rip currents in space and time off the Indian coast are minimal. However, these have long been...

An oil spill occurred off Mauritius on 6 August 2020, as merchant vessel (MV) Wakashio, with 3896 tons of heavy fuel oil (HFO) on board, struck the coral reef, causing a significant threat to the coral environment. Approximately 1000 tons of HFO leaked from the vessel. The Indian National Centre for Ocean Information Services (INCOIS) set-up an oil...

Phytoplankton pigment composition was evaluated during the pre-cyclone phase (PRCP) and post-cyclone phase (POCP) of tropical cyclone Fani in the coastal waters of the northwestern Bay of Bengal. The chromatographic analysis revealed higher pigment diversity and an increase in individual pigment concentration during POCP. Chlorophyll–a (chl–a) was...

The hydro-biological parameters such as thermohaline structure, nutrients, and chlorophyll-a (chl-a) during pre-southwest monsoon (PRSWM) and post-southwest monsoon (POSWM) periods of 2017, was investigated and compared along a coastal transect in the western Bay of Bengal (BoB). The impact of cold-core and warm-core eddies on chl-a in the very nea...

In the present work, we have operationally implemented a data assimilation (DA) scheme in the wave forecasting system at the Indian operational agency, Indian National Centre for Ocean Information Services (INCOIS). Significant Wave Height (SWH) measurements from the SARAL/AltiKa, Jason-2 and Jason-3 altimeters were assimilated using the Optimal In...

Potential fishing zone (PFZ) advisory is an essential guideline for the fishing community of India. Several studies have shown that high sea surface temperature (SST) gradient and high chlorophyll concentration in the ocean are the prospective areas for pelagic fish catch. ESSO-INCOIS provides advisories on PFZ on a daily basis using remotely sense...

Ocean State Forecasts (OSF) contribute to safe and sustainable fishing, but forecast usage among artisanal fishers is often limited. Our research in Thiruvananthapuram district in the southern Indian state of Kerala tested forecast quality and value, and how fishers engage with forecasts. In two fishing villages, we verified forecast accuracy, skil...

The coastal vulnerability to multi-hazard study aims to assess the coastal zones of Andhra Pradesh that really are vulnerable to various oceanogenic hazards. Using high-resolution coastal elevation, the maximum extent of coastal inundation during extreme high waves of cyclones & tsunamis, shoreline change, and sea-level rise can be computed. Vulner...

Over the years, continued uncertainty amid - 4 and - 5 frequency exponent representation observed in the slope of the high-frequency tail of a wind-wave frequency spectrum is a major concern. To comprehend the nature of the high-frequency tail an effort has been made to assess the slope of the high-frequency tail with measured data recorded for 3 y...

The present work describes the interaction between waves and currents utilizing a coupled ADCIRC+SWAN model for the very severe cyclonic storm Hudhud, which made landfall at Visakhapatnam on the east coast of India in October 2014. Model-computed wave and surge heights were validated with measurements near the landfall point. The Holland model repr...

About 8 years of measured wave spectra (June 2007–December 2014) off coastal Puducherry located in the east coast of India and bordering the Bay of Bengal were analyzed with an objective to understand the slope of the high frequency tail of the wave spectrum and to determine the occurrence of single peaked, double-peaked and multi-peaked spectra in...

Keywords: 1D spectrum WAM SWAN JONSWAP High frequency tail Visakhapatnam A B S T R A C T Over the past several decades, understanding the nature and slope of high frequency tail in wind-wave modelling studies is extremely important, and its uncertainty amongst −4 and −5 frequency exponent representation was an area of major significance. Hence, an...

This paper demonstrates the skill level of a wavelet neural network in improving numerical ocean wave predictions of significant wave height (H s) and peak wave period (Tp) having practical applications in operational centers. The study uses data of H s and Tp for a coastal region off Puducherry located in the east coast of India, and obtained from...

In context to application of numerical ocean wave prediction, the validation of ocean wave spectra is a research topic of active interest. This study summarizes the results of validation performed with wave spectra using SWAN model off coastal Puducherry, located in the east coast of India. The impact of wind forcing from ECMWF ERA Interim winds an...

East coast of India is characterized by low to medium topography and an extensive network of major estuaries, bays, mangrove creeks, rivers and tidal inlets that permit inland flooding during tropical cyclones. A coupled wave + surge hydrodynamic modeling system (ADCIRC + SWAN) is implemented to simulate storm surge, still water level elevation and...

Occurrence of phytoplankton bloom in the northern Arabian Sea (NAS) during the winter monsoon is perplexing. The convective mixing leads to a deeper and well-oxygenated (> 95% saturation) mixed layer. We encountered low chlorophyll conditions though the nutrient conditions were favorable for a bloom. The mean ratio of silicate (Si) to DIN (Dissolve...

The variability in zooplankton density and species composition in response to tidal oscillations were investigated in the lesser saline upper reaches (E1) and higher saline lower reaches (E2) of the Mahanadi Estuary, located at the mouth of the third largest river in Indian Peninsula. This is the first of its kind high frequency observation over th...

The present study describes the active role of met-ocean parameters on the heavy flooding that occurred during July 2018 in the Kuttanad region, Kerala. The model-derived data as well as observations showed a high anomaly of wave height in July 2018 off Kerala was not correlated with local wind anomaly and indicated possible connection of wave anom...

684276 An assessment was carried out to judge the performance of the modeled ocean currents in oil spill trajectory prediction. Ocean circulation is the key factor in determining the drift pattern of the spilled marine oil pollutant. General National Oceanic and Atmospheric Administration Operational Modeling Environment (GNOME), an oil spill traje...

686884 Determining the spilled volume of the marine oil pollutant is an essential requisite for the oil spill modellers and the responders. Generally, the mass of the spilled pollutant is computed from the total quantity and the remaining quantity of the storage tank of the distressed vessel. A method to estimate the quantity of the spilled oil pol...

A faecal indicator bacteria, Escherichia coli (E. coli), is widely used in monitoring health of estuaries, where tidal amplitude plays a critical role in its variability. Mahanadi estuary, formed at the mouth of a major tropical river Mahanadi, has large socio-economic importance. This anthropogenically stressed estuary remains understudied with re...

The end of the current decade experienced an outbreak of a new strain of coronavirus classified as severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) [coronavirus disease 2019 (COVID-19)] that spread across the globe within a short span of time and was declared as a global pandemic by the World Health Organization. In order to contain the...

Over the data sparse oceanic region, ocean surface winds from scatterometers on-board satellites play a crucial role to make accurate Numerical Weather Prediction model-based analysis. In the present study, ocean surface winds derived from the recently launched SCATSAT-1 for the year 2017 over the Indian Ocean are validated against the winds from t...

One of the significant aspects of estuarine water quality assessment is to discern the effect of tide on the environmental parameters. The variability of different physical, chemical, and biological parameters, in response to semi-diurnal tides, over a tidal cycle was investigated at contrasting salinity regimes of Mahanadi estuary. This estuary is...

A good understanding of the general circulation features of the oceans, particularly of the coastal waters, and ability to predict the key Oceanographic parameters with good accuracy and sufficient lead time are necessary for the safe conduct of maritime activities such as fishing, shipping, offshore industries etc. Considering these requirements a...

The present study examines the relationship between the tropical Indian Ocean (TIO) significant wave height (SWH) and Indian Ocean dipole (IOD) during boreal summer season (June through August) in the latest version of European Centre for Medium‐Range Weather Forecasts reanalysis (ERA5) and wave simulations forced with surface winds and sea‐ice fie...

Fishing is the most dangerous profession in the world. To reduce the number of accidents caused by capsizing of vessels, Indian National Centre for Ocean Information Services (INCOIS) has designed and developed an advisory and forecast services system for the Indian ocean regime, which warns users against potential zones and times at which vessel o...

A review of jellyfish aggregations focused on India’s coastal waters was conducted, with the aim to enhance understanding of conducive conditions and subsequent ecological impacts. Jellyfish swarming, as well as their beach strandings, have been reported from many areas of the world -including India’s coastal waters. A variety of natural (winds, ti...