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Diabetes mellitus is the leading cause of death and morbidity from long-term consequences. Antibiotic resistance is the most common treatment for diabetic foot ulcers. Chronic wounds are caused by antibiotic misuse, mistreatment of medications, and a reduction in the effectiveness of effective antibiotics in the wound or infection environment. Chemical suppression of bacterial intercellular communication, particularly quorum sensing, is of particular relevance in this regard because it regulates pathogenicity in many therapeutically relevant infections where resistance to antibiotics is a challenge. Resistance genes are also acquired through the interchange of bacterial plasmids and chromosomal. Our aim and objective is to microbiological culture study for the clinical pus samples of foot diabetic patients. Our study comprised 131 samples from diabetic foot ulcer patients, with male patients providing for 59% and female patients accounting for 41%. In 131 sample progressing reports, 81 isolates were discovered, ranging in age from 40 to 80 years. The most commonly infected age groups are 51 to 60, with the majority of infection cases categorized as grade III. A sample was taken. The sample grew 97 percent of the time and grew just 3% of the time, with mono microbial growth 48 percent of the time and poly microbial growth 49 percent of the time. MDR Gram positive staphylococci 14 isolates and gram negative pseudomonas 11 isolates showed resistance to 25 culture DNase enzyme activity. In staphylococci 9 isolates and pseudomonas 6 isolates, the DNase enzyme activity in DNase agar media light zone formed. In conclusion diabetic foot ulcers are one of the most prevalent, expensive, and serious consequences of diabetes, and they are considered a major public health issue. Early diagnosis and successful therapy require accurate identification of the causative microorganisms.

In the Bay of Bengal, the warm, dry boreal spring concludes with the onset of the summer monsoon and accompanying southwesterly winds, heavy rains, and variable air–sea fluxes. Here, we summarize the 2018 monsoon onset using observations collected through the multinational Monsoon Intraseasonal Oscillations in the Bay of Bengal (MISO-BoB) program between the United States, India, and Sri Lanka. MISO-BoB aims to improve understanding of monsoon intraseasonal variability, and the 2018 field effort captured the coupled air–sea response during a transition from active-to-break conditions in the central BoB. The active phase of the ∼20-day research cruise was characterized by warm sea surface temperature (SST > 30°C), cold atmospheric outflows with intermittent heavy rainfall, and increasing winds (from 2 to 15 m s−1). Accumulated rainfall exceeded 200 mm with 90% of precipitation occurring during the first week. The following break period was both dry and clear, with persistent 10–12 m s−1 wind and evaporation of 0.2 mm h−1. The evolving environmental state included a deepening ocean mixed layer (from ∼20 to 50 m), cooling SST (by ∼1°C), and warming/drying of the lower to midtroposphere. Local atmospheric development was consistent with phasing of the large-scale intraseasonal oscillation. The upper ocean stores significant heat in the BoB, enough to maintain SST above 29°C despite cooling by surface fluxes and ocean mixing. Comparison with reanalysis indicates biases in air–sea fluxes, which may be related to overly cool prescribed SST. Resolution of such biases offers a path toward improved forecasting of transition periods in the monsoon.

The characteristics of surface currents during November 2016–October 2017 are studied using observations from the high-frequency radars (HFRs) and a moored buoy (BD12) along the western Andaman Sea (WAnS). The comparison of HFR currents with the collocated currents from BD12 shows a high correlation (>0.78) on a daily scale for both the components. Moreover, the daily HFR currents compared reasonably well to the composite daily surface currents from multiple satellites for both the zonal and meridional components. The reversal of currents is observed during the northeast (November–February) and southwest (June–October) monsoons with the mean current magnitudes of 0.41 m/s northward and 0.22 m/s southward, respectively, which is predominantly influenced by the local wind stress. The seasonal reversal of currents leads to the exchange of waters between the WAnS and the Bay of Bengal through the 11° channel, which is primarily due to the Ekman mass transport. Harmonic analysis of the hourly data from HFRs shows the dominance of M2 tidal currents, followed by other semidiurnal (S2, N2), diurnal (K1, O1), and shallow water constituents (M4 and MS4). Also, the tidal constituents from both the current observations matched in their relative order of amplitudes with a reasonable correlation (0.95). Total tidal variance ranges between 10% and 50% in the WAnS, with the highest contributions from the M2 tidal currents (of 25%). Moreover, stronger M2 tidal currents are observed to skirt around Little Andaman (LA) Island extending out to 100-km offshore, with maximum amplitudes of 12 cm/s.

Temperature and salinity are essential ocean variables for understanding the oceans' physical processes. The conductivity and temperature measurements are used for deriving ocean salinity. Conductivity-temperature (CT) sensors mounted on moored buoys are widely used to collect sustained time-series observations of temperature and salinity. However, these measurements are prone to drifts that need to be corrected to ensure data quality. The present study evaluates a field validation technique to correct the drift in subsurface temperature and conductivity measurements that can potentially complement the standard calibration procedure performed by the original equipment manufacturer. The advantage of field validation is that it could be carried out soon after retrieving CT sensors, which ensures that the physical conditions and configuration of the retrieved CT sensors remain unaltered from that of the in-situ conditions. The drift in the CT sensors was analyzed by pre-deployment and post-retrieval field validation of CT sensors. A correction is applied to the raw data assuming a linear trend in drift with time. An ice test to identify and correct the errors in the timestamp of CT measurements is also discussed.

Diabetes mellitus is a very serious systemic disease worldwide. Around 416 million cases were estimated in 2015 worldwide, and are expected to reach 549 million in 2030 which is 8.6% higher. Diabetes mellitus is the leading cause of mortality and morbidity and is responsible for 3.8 million deaths annually. 25% of the diabetic patients are affected with foot infections out of which, 15% people are forced for limb amputation which affects the quality of life of the patients. Diabetic foot ulcer is a poly microbial infection mostly occurs due to Staphylococcus spp and Pseudomonas spp and pose serious complications. Bacteria are the cause for much type of diseases and generate resistance to wide range of biofilm forming. Biofilms constitute reservoirs of pathogens and are associated with resistance to antimicrobial agents and chronic infection. The study included 156 patients (59% male and 41% female) suffering diabetic foot ulcer whose pus culture was isolated. The identification of isolates for both gram-negative and gram-positive organisms was done as per the procedures mentioned in Bergey’s manual of Determinative Bacteriology. Further, MALDI- TOF (Matrix-Assisted Laser Desorption/Ionization) was used to confirm the identification of the isolates using classical methods. Staphylococcus spp (65%) and Pseudomonas spp (35%) biofilm producing isolates were identified for Congo red method assay and Tissue culture plate method. Results of biofilm production in positive, intermediate, negative differentiation on the Congo red plate assay and Tissue culture plate method assays were analyzed.

Diabetic foot ulcers are still a problem for the health care system and are majorly influencing quality of life. Infected foot ulcer is one of the most feared complications of diabetes mellitus, leading to gangrene and it needs to be amputed. Diabetic foot lesions are major medical, social and economic problem and leading cause of hospitalization for patients with diabetes worldwide. The risk of a diabetic patient for developing a foot ulcer was estimated to be ~25%. Samples were collected from 65 infected patients of diabetic foot ulcer male and female. The mean age group was found to be 40-80 years with the clinical history such as age, sex, types of diabetes duration of diabetes, size of ulcer and duration of ulcer were observed and recorded. The Specific mediums were used for the isolation and identification using classical methods based on their morphology, Grams stain reaction, oxidase and catalase tests were performed to confirm the isolates were both gram-negative and gram-positive organisms Bergey’s manual of Determinative Bacteriology. Further, MALDI- TOF (Matrix-Assisted Laser Desorption/Ionization) was used to confirm the isolates identified in classical methods were Staphylococci (79%) and Pseudomonas (21%) In this study Among 68 isolates, identified in out of 41 isolates Pseudomonasaeruginosa (21%) Staphylococcus aureus (54%) Staphylococcus hominis (20%)and Staphylococcous hemolytic(5%). Although in gram positive organism Staphylococcus aureus (54%) was the most predominant isolate found in diabetic foot ulcer.

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).

The article proposes a novel and robust Continuously Homing Submerged Autonomous Tsunami Underwater System (CHATUR) in which the buoy is submerged at a depth of 300 m, collecting sea-level data during normal conditions and surfacing during a tsunami event to transmit the event data. By on-demand reliability analysis, a system in the Bay of Bengal requires health monitoring at an interval of 13 days. By offshore experiments and numerical simulations, the configuration increases the tsunami warning time by ~2 min.

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, and offshore industries. Considering these requirements and buoyed by the advancements in the field of ocean modeling, data assimilation, and ocean observation networks along with the availability of the high-performance computational facility in India, Indian National Centre for Ocean Information Services has set up a “High-Resolution Operational Ocean Forecast and Reanalysis System” (HOOFS) with an aim to provide accurate ocean analysis and forecasts for the public, researchers, and other types of users like navigators and the Indian Coast Guard. Major components of HOOFS are (i) a suite of numerical ocean models configured for the Indian Ocean and the coastal waters using the Regional Ocean Modeling System (ROMS) for forecasting physical and biogeochemical state of the ocean and (ii) the data assimilation based on local ensemble transform Kalman filter that assimilates in situ and satellite observations in ROMS. Apart from the routine forecasts of key oceanographic parameters, a few important applications such as (i) Potential Fishing Zone forecasting system and (ii) Search and Rescue Aid Tool are also developed as part of the HOOFS project. The architecture of HOOFS, an account of the quality of ocean analysis and forecasts produced by it and important applications developed based on HOOFS are briefly discussed in this article.

The ocean plays a major role in climate change, and its impact has an extreme effect on the process of coastal and other activities around the globe. The comprehensive analysis of long-term wave climate is carried out at selected locations in the western Bay of Bengal (BoB), by observing the distribution of significant wave height (SWH) using monthly averaged satellite and WAM model for 20 years (1996–2015). The data used in this study were compared with two in situ buoy observations obtained from the National Institute of Ocean Technology (NIOT), Chennai, India. The satellite and wave model (WAM) data show a good correlation with both in situ buoy observations. The probability distribution functions indicated a significant increase in the higher range of SWH during the recent decade. The analysis of 20-year SWH indicates a positive trend with significant annual and semiannual periodicities. The northwestern bay depicts higher energy in the annual cycle, whereas the southwestern bay exhibits equal contributions from annual and semiannual cycles. The study also reveals that the increasing trends in local SWH in the western BOB are modified due to the number of tropical cyclones as well as the migrating swells generated in the southern Indian Ocean.

Based on the in-situ subsurface thermal and salinity measurements from the Ocean Moored Buoy Network for Northern Indian Ocean (OMNI) during the passage of very severe tropical cyclones (TCs) in the Bay of Bengal, we have identified that the depth of ocean‐atmosphere interaction is limited by the depth of the pycnocline. During the TC Vardha and Phailin with cyclone-period-averaged wind speeds of 8 and 21 m/s, respectively, the maximum possible rates of water-vapor generation during the cyclone period, computed based on the salinity changes and considering precipitation, are 1.0 and 9.3 kg/m2/h, respectively. For the same wind speeds, based on the ocean heat content (OHC) changes, it is quantified that ~78% and 89% of the OHC changes are in the form of latent heat. The real-time availability of the in-situ subsurface parameters can be used in the ocean-atmosphere coupled models and intensification studies.

Reliable performance is the key requirement for deep ocean wave measurement buoys as failures lead to loss of data and expensive reinstallations. From more than 0.37 million demanding offshore wave measurement buoy-hours, the data returns from the buoys operating in the Bay of Bengal and the Arabian Sea were 88% and 95%, respectively. The mean time between failures of the buoys was 1.8 years in the Bay of Bengal and 3.8 years in the Arabian Sea, and the mean time to restore was 90 and 68 days, respectively. The offshore failure events, the technical developments for improving the performance, and the strategies adopted to mitigate the failures are presented in detail. The significance of the technical features incorporated for improving the reliability of the wave measurement buoy subsystems is quantitatively represented through fault tree modeling and simulations based on standards and the field failure data.

Sustained real-time ocean observation systems using moored data buoys are vital for understanding ocean dynamics and variability, which are essential for improving oceanographic services including weather prediction, ocean state forecast, cyclone tracking, tsunami monitoring, and climate change studies. This paper describes the significant rapid restoration techniques implemented to increase the availability of the Indian Ocean observation networks over the past two decades. The efforts have helped in achieving availability of 97.9%, 82.3%, and 98.7% for the meteorological sensors, subsea surface oceanographic sensors, and tsunami buoy network, respectively.

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 conditions and surface forcing based on moored observations, shows that cyclone winds rapidly eroded the shallow, salinity-dominated density stratification and mixed the upper ocean to 40–50-m depth, consistent with observations. Model sensitivity experiments indicate that changes in ocean mixed layer temperature in response to Cyclone Phailin are small. A nearly isothermal, salinity-stratified barrier layer in the prestorm upper ocean has two effects. First, near-surface density stratification reduces the depth of vertical mixing. Second, mixing is confined to the nearly isothermal layer, resulting in little or no SST cooling.

The contrasting upper ocean responses of the Bay of Bengal to two intense cyclones, Phailin and Hudhud, which traversed similar paths and occurred at nearly the identical time of year, were analysed using observations from moored buoys, satellite observations, and modelling. Our analyses revealed that the upper ocean was highly stratified prior to Phailin compared to the case for Hudhud. The stratification in the near surface prior to the onset of Phailin (Hudhud) was predominantly driven by vertical gradients in salinity (temperature). The upper ocean response to the passage of Phailin (Hudhud) was characterised by notable changes in sea surface salinity (sea surface temperature). In addition, enhancement of chlorophyll-a was observed over an extensive area following the passage of Hudhud but was confined to a mesoscale eddy after Phailin. The presence of strong near-surface haline stratification sustained temperature inversion and resulted in weak sea surface temperature cooling in the wake of Phailin. The mixing centred along the trajectory of a cyclone in a haline (thermally)-stratified ocean leads to fronts having strong horizontal haline (thermal) gradients in the wake. Cross-front ageostrophic submesoscale circulation features resulted in rapid fluctuations of salinity in the wake of Phailin and temperature in the wake of Hudhud. The cross-front ageostrophic circulation features and post-storm winds played a critical role in controlling mixed layer restratification after the cyclones.

This paper describes the development and performance validation of a cylindrical surface buoy (CSB) used for monitoring tsunamis in Indian seas. The buoy design with multiple compartments provides damage-tolerance curved top surface profile, the subsurface access ensures vandalism resistance, and the shape provides enough space for the power and control systems for an offshore endurance of two years. The scaled-down CSB is numerically modeled and experimentally validated for its stability in a wave basin. The validated numeric model is extended to a diameter of 2.4 m and the mooring loads are analyzed. The field scale prototype CSB is deployed in the open ocean, where the water depth is 2500 m. The performance of the CSB is validated from one year of failure-free performance and capability to remain within the watch circle under all environmental conditions, and it has detected the water level change events during the operational period.

Conductivity and Temperature (CT) sensors are attached in the Ocean Moored buoy network in Northern Indian Ocean (OMNI) at different depths upto 500 m below the sea surface. Drift in these sensors were analyzed based on the result of calibration. For detailed investigation, the sensor's drift is categorized based on the position of sensors in the mooring as surface layer (above 50 m), thermocline layer (50–200 m) and deep layer (200–500 m) and analysis was carried out at both Arabian Sea (AS) and Bay of Bengal BoB. The drift analysis revealed that over the time of deployment the drift in temperature sensor was very minimal and well within the accuracy limit. However, the drift in the conductivity sensors was more significant. Drift in the conductivity sensor decreases as the deployment depth of the sensor increases and also drift in the sensors which were deployed in AS is high as compared to the sensors deployed in BoB. Biofouling of the sensor is measured spatially in AS and BoB and it indicates that biofouling and Abrasive scouring of cells are due to the flow of high concentrations of plankton in the euphotic zone(top layer), which may cause the drift in the conductivity sensor.

Sustained real-time ocean observation systems using moored data buoys are vital for the understanding of ocean dynamics and variability to improve oceanographic services such as weather prediction, ocean state forecast, cyclone tracking, tsunami monitoring, and climate change studies. The Indian Tsunami Buoy System (ITBS) developed and operated by the National Institute of Ocean Technology (NIOT) provides vital inputs to the Indian Tsunami Early Warning System (ITEWS) by confirming the propagation of tsunami in the deep ocean; estimating its travel time to the shore; assessing possible impacts on the coastline of the Indian Ocean rim countries during a Tsunamigenic earthquake. The ITBS presently comprises a network of 4 moored surface buoys (MSB); two systems (2) in the Bay of Bengal (BoB) and two systems (2) in the Arabian Sea. The MSB transmits the received data to the INMARSAT satellite terminal, which, in turn, transmits it to the NIOT and Indian National Center for Ocean Information Services (INCOIS) data analysis center, through the Land Earth Station and public networks. Continuous improvements in energy storage, satellite-based communication, deep ocean moorings & data analysis tools and by following standards & best practices, the Mean Time Between Failure (MTBF) of a tsunami buoy communicating from the location to the NIOT-Mission Control Center (NIOT-MCC) through INMARSAT telemetry has been increased from 0.3 years in 2007 to 0.9 years in 2015. They include processor health monitoring using health monitoring module in which the heart beat pulse of the Data Acquisition System (DAS) is monitored by the microcontroller and restores functions when there is a functional interruption. Features to reset the processor hardware during prolonged outages, remote calibration facility and mooring watch circle which are aimed at increasing the availability of the time-critical system are also incorporated. The 4 node network has recorded a MTBF of 1.62 years, with a system availability of 98.3%. The required minimum maintenance interval has increased from 12 months to 24 months. Based on the achieved MTBF, maintenance experiences and the ship availability, the tsunami buoy systems (TBS) are maintained based on a 4-slot annual maintenance program. A DAS with energy-efficient design helps in decreasing the energy consumption and increases the offshore endurance of the MSB thereby reducing the required ship time and the huge maintenance costs involved. A distributed battery configuration, in addition to reduced energy consumption has advantages in operating a section of the DAS during battery failures, which increases the partial availability of the DAS. In a scenario, when the battery pack powering the telemetry fails, the pressure sensor monitoring and processing circuit remains healthy, enabling data availability for post-event analysis. This article describes the development and performance validation of the energy-efficient and reliable data acquisition system (DAS) for ITBS. The moored surface buoy (MSB) with the customized DAS, data encryption techniques, distributed battery architecture with 6-hour reporting interval helps in reducing the MSB power consumption from 5.5Ah to 0.79Ah/day and DAC annual probability of failure from 2.6 to 0.4%. The field performance of the system is validated from April 2019 for 200 days of interruption-free continuous offshore operation in the prototype tsunami buoy system at the location 18° 38’ 9.6” N, 67° 11’ 34.8 E in the Arabian Sea. By implementing this development in the ITBS will improve the reliability and reduce energy costs.

Autonomous platforms already make observations over a wide range of temporal and spatial scales, measuring salinity, temperature, nitrate, pressure, oxygen, biomass; and many other parameters. However, the observations are not comprehensive. Future autonomous systems need to be more affordable, more modular, more capable and easier to operate. Creative new types of platforms and new compact, low power, calibrated and stable sensors are under development to expand autonomous observations. Communications and recharging need bandwidth and power which can be supplied by standardized docking stations. In situ power generation will also extend endurance for many types of autonomous platforms, particularly autonomous surface vehicles. Standardized communications will improve ease of use, interoperability, and enable coordinated behaviors. Improved autonomy and communications will enable adaptive networks of autonomous platforms. Improvements in autonomy will have three aspects: hardware, control, and operations. As sensors and platforms have more onboard processing capability and energy capacity, more measurements become possible. Control systems and software will have the capability to address more complex states and sophisticated reactions to sensor inputs, which allows the platform to handle a wider variety of circumstances without direct operator control. Operational autonomy is increased by reducing operating costs. To maximize the potential of autonomous observations new standards and best practices are needed. In some applications, focus on common platforms and volume purchases could lead to significant cost 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 EGO for the emerging glider operations 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.

Air-Sea interaction in the Bay of Bengal has a strong coupling with the Monsoon rains over the South Asian region. The wet and dry spells, or active-break cycles of the Asian summer monsoon are governed by different modes of intra-seasonal variability with implied northward and westward propagation. Multiple hypotheses exist as to how air-sea interaction and the ocean mixed layer influence the propagation of Monsoon Intra-seasonal Oscillations (MISO), but the multi-scale nature of atmosphere-ocean coupling is not well understood. Multi-country collaborative initiatives MISOBOB (Oceanic Control of Monsoon Intra-seasonal Oscillations in the Tropical Indian Ocean and the Bay of Bengal-USA), RIO-MISO (Role of the Indian Ocean on Monsoon Intra-Seasonal Oscillations-USA), and OMM (Ocean Mixing and Monsoons-India) have led to a combination of ocean observations, atmospheric observations, and associated modeling to study this phenomenon. We present observations analyzed using the OMNI (Ocean Moored Buoy Network for Northern Indian Ocean) buoy network of India and RAMA 15N mooring along with MISOBOB field program in June 2018, which captured the onset of the 2018 Monsoon from a heavily instrumented ship that simultaneously made measurements in the atmospheric and oceanic boundary layers. The shortwave and net heat fluxes show dramatic changes during the active phase with the in-situ net heat flux reversing sign. The Monsoon onset cooled all of the Central and North Bay of Bengal by 1.5 K, leading to large heat losses in the Bay, as the oceanic surface mixed layer deepened from 20m to about 40m. This talk will also explore the role of sub-surface salinity stratification in modulating cooling of the upper ocean at multiple locations across the Bay, providing a basin-wide view. Observations suggest that the air-sea interaction and ocean stratification in the Bay likely has strong feedback on the organized convection in the atmosphere.

The sensitivity of latent heat flux to the warming phase of intra-seasonal oscillation in the Bay of Bengal is studied with the help of in-situ data. This was analyzed from 2012 to 2015 with the help of data obtained from moored buoys deployed in the northern Bay of Bengal. The annual secondary peaks in sea surface temperature is observed in the northern Bay of Bengal associated with the warming phase of the intra-seasonal oscillation during southwest monsoon season, with net heat flux dominantly governing the mixed layer temperature. An increase in the release of latent heat flux from the northern bay is observed with the warming phase of intra-seasonal oscillation, which again leads to cooling of sea surface temperature. Higher latent heat flux release associated with the intra-seasonal warming phase during southwest monsoon season has intrigued us to study the sensitivity of latent heat flux with sea surface temperature. The sensitivity of gradient in saturation specific humidity is comparatively higher than the sensitivity of wind speed to sea surface temperature variations during southwest monsoon season. The gradient in sea–air saturation specific humidity is largely driven by saturation specific humidity of air (Qa) during both the seasons. However, the correlation of gradient in saturation specific humidity with surface saturation specific humidity is higher during southwest monsoon season compared to northeast monsoon season. Thus, the warming phase of sea surface temperature associated with intra-seasonal oscillation during southwest monsoon season always lead to an increase in latent heat flux release, favoured by high sensitivity of surface saturation specific humidity to variations in sea surface temperature.

With land-based resources depleting fast, sustained harvesting of ocean resources with an appropriate trade-off between economic growth, social needs, and the health of the ocean environment is essential. India, with an over 7600-km-long coastline, an exclusive economic zone of 2.3 million km2, and seeking extension for additional 560 km, has initiated blue economic policies for leveraging the growth of the national economy. The first part of the paper presented in the OCEANS '18 conference in Kobe discussed the technology initiatives to harness the vast living and nonliving blue economic resources in India, including deep-ocean minerals, hydrocarbons, renewable energy, ocean desalination, and bioprospecting. This paper describes the activities carried out related to the activities undertaken by the National Institute of Ocean Technology (NIOT) in the areas of coastal protection, cyclone and tsunami early warning systems, coral habitat observations, sustainable fishing, and numerical studies carried out to understand the influence of natural gas leaks on deep-ocean ecology.

Ambient noise field and propagation in a glacierized Arctic fjord, Kongsfjorden is investigated using time series measurements of noise and Conductivity Temperature Depth (CTD) measurements between July 2015–April 2016. The hydrophone recorded noise for 10 months, with a duty cycle of 1 min every 3 h, covering summer, fall, winter and spring season. Noise field is seen to be variable with highest levels recorded during summer-fall (112 dB at 0.125 kHz) after which there is a decrease in maximum recorded noise levels. The spectral distribution of noise deviates from the theoretical Gaussian assumption, at varying degrees over the frequency band (0.125–4 kHz). Low frequency band is dominated by marine traffic during summer and fall, and ice wave interactions during winter and spring months. Propagation studies reveal variable nature in propagation with different scenarios observed between seasons. During the summer, refracted paths are observed and a weak channel is formed around the sound channel axis (∼100 m), and a well defined surface duct is revealed during the fall (depth of ∼60 m), characterized by a lower half channel bounded by the sea surface and the sonic layer depth. Surface duct propagation is common in winter with an upward profile and weakens with the onset of spring, as a consequence of the hydrology at the region. The studies will be useful in the context of climate change owing to the critical location of Kongsfjorden which is more prone to experience ongoing warming.

The Bay of Bengal (BoB) is a distinct oceanic region for mesoscale oceanic eddies. The sea level anomaly from the Archiving, Validation, and Interpretation of Satellite Oceanographic (AVISO) help to identify an unusual anti-cyclonic eddy (ACE) over head BoB during May–July 2014. Two Indian moored buoys (BD08 and BD09) located over this region aided to study the subsurface thermohaline structures of the ACE. Compared to no-eddy environment, the temperature and salinity showed an increment of ~ 3–4 °C and ~ 1–2 PSU, respectively, during the ACE life period. The temperature and depth of the isothermal layer at genesis (peak) stages are increased to ~ 30 °C (~ 30.7 °C) and ~ 20 m (30 m) when compared with no-eddy conditions (28.2 °C and 10 m). The thermocline depth is deepened to 75 m at the peak stage, while it is 50 m in no-eddy condition. A temperature difference of 3 °C between no-eddy and peak stages of ACE is observed up to 50 m. The ocean heat content (OHC) at BD08 (BD09) during genesis and peak stages has increased by ~ 72% (~ 50%) and ~ 247% (~ 181%), respectively, when compared with no-eddy conditions. Moreover, the MOHC also shows a similar increment of ~ 125% (~ 123%) and ~ 258% (~ 284%), respectively. A noticeable influence is seen in turbulent fluxes and lower atmospheric variables during eddy life. This study highlights the capability of moored buoys in understanding the subsurface thermohaline features of the eddies over northern BoB.

In this study, the upper ocean and subsurface variability during the different phases of the cyclonic storm ROANU along the western Bay of Bengal (BoB) in May 2016 are investigated by using the moored buoys, Argos, HF radar and satellite datasets in the proximity of the cyclone track. The moored buoy observations recorded a decrease of sea surface temperature (SST) by ~ 1 °C all over the track, whereas increase in salinity by ~ 1.5 PSU was detected along with the highest wind speed of 16 m s−1, pressure drop of 14 hPa and air temperature drop of 4 °C. The cooling at the cyclone centers from the satellite data indicated higher (lower) SST drops when translation speed of the cyclone was low (high) and took more (less) time to recover to its pre-cyclone state in southern (northern) BoB. Mostly, higher SST drop was observed along the right side of the cyclone track. Interestingly, the opposite phenomenon occurred before landfall, where SST drop was higher on the left due to upwelling in the head bay as observed both from wave rider buoy (WRB) at Digha and satellite SST. The WRB near Vizag showed the maximum increase in significant wave heights by ~ 2.4 m during the passage of cyclone. Argos also captured cyclone-induced drop in temperature due to upwelling and entrainment reasonably well. In the southwestern bay, significant upwelling was observed from the Argos with drop in temperature and increase in salinity in the upper layers. However, a strong stratification was observed from Argos in the northwestern BoB due to lesser salinity and higher precipitation. The currents from in situ as well as HF radar datasets measured the increase in current magnitude during the passage of ROANU. Rotary spectral analysis showed strong inertial currents with frequency ~ 2.1 days at BD11 location, with higher amplitudes of the clockwise component during the cyclone period.

Over the past two decades, the Indian Ocean moored surface buoy observation networks have expanded in the spatiotemporal domain and technologically matured with system reliability, availability, cost optimization, and precision measurement of meteorological and oceanographic parameters as the key targets. Based on the return of experiences in the development, operation, and maintenance of the moored buoy observation networks over two decades, this paper for the first time summarizes the reliability metrics achieved by the National Institute of Ocean Technology (NIOT)-operated moored buoy networks, the healthiness monitoring interval implemented to achieve the highest level of on-demand reliability, the methodologies adopted to ensure highest possible system availability, and data returns. The tsunami buoy network with two buoys and the meteorological buoy with cyclone tracking sensors are found to have a mean time between failure of 1.27 years and 0.5 years, respectively. The identified performances provide a baseline for defining the technical improvement targets, identifying alternate technologies, incorporating redundancies, cost optimization, and maintenance planning. The approach serves as a reference for reliability assessment and integrity management of similar moored buoy ocean observation networks and for evolving standards for oceanographic systems.

A study of the inter-annual variability of the warming of the southeastern Arabian Sea (SEAS) during the spring transition months was carried out from 2013 to 2015 based on in situ data from moored buoys. An attempt was made to identify the roles of the different variables in the warming of the SEAS (e.g., net heat flux, advection, entrainment, and thickness of the barrier layer during the previous northeast monsoon season). The intense freshening of the SEAS (approximately 2 PSU) occurring in each December, together with the presence of a downwelling Rossby wave, supports the formation of a thick barrier layer during the northeast monsoon season. It is known that the barrier layer thickness, varying each year, plays a major role in the spring warming of the SEAS. Interestingly, an anomalously thick barrier layer occurred during the northeast monsoon season of 2012–2013. However, the highest sea surface temperature (31 °C) was recorded during the last week of April 2015, while the lowest sea surface temperature (29.7 °C) was recorded during the last week of May 2013. The mixed layer heat budget analysis during the spring transition months proved that the intense warming has been mainly supported by the net heat flux, not by other factors like advection and entrainment. The inter-annual variability analysis of the net heat flux and its components, averaged over a box region of the SEAS, showed a substantial latent heat flux release and a reduction in net shortwave radiation in 2013. Both factors contributed to the negative net heat flux. Strong breaks in the warming were also observed in May due to the entrainment of cold sub-surface waters. These events are associated with the cyclonic eddy persisting over the SEAS during the same time. The entrainment term, favoring the cooling, was stronger in 2015 than that in 2013 and 2014. The surface temperatures measured in 2013 were lower than those in 2014 and 2015 despite the presence of a thick barrier layer. The substantial decrease in net heat flux along with entrainment cooling has been identified as causes for this behavior.

The work identified the monsoon intraseasonal oscillation (MISO) from the observed met-ocean parameters from the moored buoys and satellite datasets during June 2013 – September 2013. The 30–60 days bandpass filtered winds, sea surface temperature (SST), and rainfall from both the satellites and moored buoys have indicated the existence of active and break phases of MISOs with a periodicity of 10–12 days. All the parameters show a northward propagation of the MISO signals from the southern to the northern BoB with stronger magnitude on the north of 12 °N. The warmer SST causes the high wind and precipitation in an active phase after 4–5 days. During active phases, SST dropped, and break phase occurs with less wind and precipitation after 10–12 days. Prominent signatures of the MISOs are also observed along the ocean subsurface from the temperature, salinity, and current profiles. The 23 °C isotherm (D23) deepens during the active phases of the MISOs to make the surface warm. The D23 shoals during the break phases, indicating cooling of the ocean surface. The in-phase relationship of 100 m temperature and wind speeds together indicate an important role of the surface winds during the different phases of MISO. Deepening and shoaling of mixed layer are observed in the upper ocean during the different MISO phases with varying characteristics in the northern and southern BoB. The subsurface signatures of MISOs are strong near 100 m for temperature, but for salinity and currents, the signatures are restricted within 50 m depth.

Based on the in-situ subsurface thermal and salinity measurements from the Ocean Moored buoy network for Northern Indian Ocean (OMNI) during the Super Cyclone Amphan in the Bay of Bengal during 14–18 May 2020, we have identified that the ocean-atmosphere interaction is limited to 80 m, the depth of the pycnocline. Using the OAEE-TS algorithm and dynamic changes in the sea subsurface temperature, salinity and precipitation as inputs, we have calculated the water vapor generation rates for a range of wind speeds. Based on the salinity changes, the water vapor generation rates for cyclone period-averaged wind speeds of 9, 16 and 25 m/s were 0.86, 4.33 and 11.24 kg/m2/h, respectively. For the same wind speeds, based on the Ocean Heat Content (OHC) changes, ∼76, 86 and 95 % of the OHC changes were in the form of latent heat. The identified evaporation rate parameters along with the previous study results are presented as model which could be used as inputs for ocean-atmosphere coupled models and tropical cyclone intensification studies in the Bay of Bengal.