Moored Data Buoys Research Articles

Advanced Moored Data Buoys for Catching Typhoons in the Western North Pacific

Abstract With the western North Pacific being one of the most active typhoon hotspots, a reliable buoy system is essential for in situ observations during typhoon passages. This study details the development and implementation of two improved buoys designed by National Taiwan University based on the Autonomous Temperature Line Acquisition System. It aims to establish a buoy network for near real-time, high-resolution meteorological and oceanic data collection during typhoon periods in the western North Pacific. The buoy system was distinguished by its reliable design, low power-consumption system, dual satellite and radio communication system, and inductive modem-based data acquisition system. Moreover, the system was proven robust to extreme weather conditions and fishing challenges. From 2015 to 2022, we conducted sea trials in typhoon hotspot regions every summer (normally June to October), demonstrating the buoys' durability and capability to withstand 21 typhoons while collecting valuable scientific data.

Indigenization of Buoy Components Using Additive Manufacturing Technique

The Ocean Observation Systems (OOS) group of the National Institute of Ocean Technology (NIOT) is involved in the design, development and sustenance of moored data buoys in the Indian Seas. The moored buoy systems deployed in the Northern Indian Ocean provide real-time, continuous observation of surface meteorological and oceanographic parameters which help in monitoring extreme weather events and natural disasters such as cyclones and tsunamis. Buoy components are of different sizes and shapes and are made of various materials, including metals and plastics. However, due to unique and critical design requirements, the development of deep-sea components faces hurdles caused by manufacturing limitations. The advent of additive manufacturing (AM) has met the demand for quickly producing parts. Due to the high pressure and low temperature conditions, it is extremely difficult to design and develop deep sea components. Consequently, High Impact Polystyrene (HIPS) material has been selected for the subsurface floats. The float is manufactured using the Fused Deposition Modeling (FDM) additive manufacturing technique in the Fabheads 1K FDM printer with pellet based extrusion method. These subsurface floats are used at a water depth of 500 m in NIOT buoy systems, with a working pressure of approximately 50 bar. Taking a factor of safety of two into account, the part is designed to withstand 100 bar. To assess the component's performance under deep-sea hydrostatic conditions, it underwent testing in the hyperbaric chamber test facility at NIOT. During the qualification process, the component successfully withstood the design pressure of 100 bar and imploded at 102 bar. This study is part of NIOT's ongoing efforts to indigenize deep-sea components using AM and assess its future prospects.

India's Ocean Observation Network: Relevance to Society

AbstractSustained and real-time ocean observation systems using moored data buoys are vital for understanding ocean dynamics and the variability required for improving oceanographic services, including weather prediction, ocean state forecast, and climate change studies. This paper presents the effectiveness of India's moored data buoy network in capturing the response in the ocean during the cyclonic disturbances formed in the Bay of Bengal (BoB) and the Arabian Sea (AS) during the last 5-year period. The moored buoy network provided critical information about the evolution and intensification of low-pressure systems and supported the India Meteorological Department to improve prediction capabilities by incorporating real-time data. The lowest mean sea-level pressure of 920 hPa was recorded in the BoB during the very severe cyclonic storm Phailin. The warning systems adopted for the effective dissemination of the ocean forecast services to the user community have significantly reduced the loss of life and property in coastal states.

Analysis of Composite Instrument Housing of Sensor Buoy Subjected to Mooring Loads

Moored data buoys are offshore platforms, fitted with meteorological and oceanographic sensors anchored at various locations in the ocean. The data is transmitted through satellite to the shore station facility. It consist of an instrument housing which is made up of aluminium 6061-T6 alloy. Several disadvantages of the current instrument housing material are its vulnerability to galvanic corrosion, maintenance cost and its heaviness. In order to avoid these shortcomings, a composite instrument housing made up of glass fibre vinyl ester (GFVE) cylinder is proposed. Two ply configurations, 22 layered with all ±90° orientation, and 22 layered with ±90° for extreme plies and ±30° for intermediate plies are analyzed for compressive service loads, in ABAQUS software package. Stress contour plot of the cylinder and ply-wise stress plots along thickness are obtained and discussed. It is concluded that that the stresses induced in cylinder with all ±90° orientation is 5.5% less than the configuration with both ±90° and ±30° at the extreme and intermediate plies respectively.

Verification of model wave heights with long-term moored buoy data: Application to wave field over the Indian Ocean

This paper describes the results obtained using a modified version (ModWAM) of the global wave model WAM, in which new parameterizations have been applied based on the seasonal changes and extreme weather events that have occurred in the Indian Ocean. Model significant wave heights (Hs) have been verified using Hs data extracted for the period 2000–2006 from 10 moored data buoys, deployed in the north Indian Ocean. Satellite altimeter Hs has also been used for the model comparison. Based on the error estimates of significant wave heights and spectral wave energy, improvement achieved in wave prediction using ModWAM is demonstrated. We find that the ModWAM improved the accuracy of significant wave height prediction in deep water considerably (rmse of ModWAM is less than that of rmse of WAM), and provided better presentation for high waves that prevailed during southwest monsoon (e.g. Hs, of the order of. 6.0m in June 2005) and extreme weather events (e.g. cyclone that occurred in May 2005), compared to WAM; but, it still underestimates Hs for high waves. Comparison between modeled and measured spectra shows that ModWAM overpredicts spectral energy at low frequencies, and underpredicts at high frequencies.

Validation of in situ wave spectrum with JONSWAP in the Indian Ocean

The moored data buoys deployed by the National Institute of Ocean Technology (NIOT) are floating platforms designed to carry a specific suit of sensors to measure wave parameters. Waves are measured by the Motion Reference Unit (MRU), which outputs roll, pitch, compass, and heave. These data are recorded at a rate of 1 Hz for 17 minutes every three hours. For this study, wave measurements were carried out at two locations (deep and shallow water) over the same period. The wave spectra were generated from the hard disk data (roll, pitch, heave, and compass) of the moored buoys. A Matrix Laboratory (MATLAB) program was developed for generating the wave spectrum using the hard disk data. The spectrum exhibits significant features for deep- and shallow-water buoys. In a single peak spectrum the dominant peaks are observed at 0.08 and 0.1 Hz and the multi-peak spectrum energy is distributed over a wide range, from 0.05 to 0.25 Hz. The buoy spectra were compared to the Joint North Sea Wave Project (JONSWAP) spectrum in deep- and shallow-water locations in the Bay of Bengal, and also the deep-water buoy spectrum was compared to the wave model (WAM) output spectrum in the Arabian Sea. The JONSWAP spectrum mostly conforms to the buoy spectrum in regard to marine wind conditions.

How to Deploy the Moored Data Buoy with Small Vessel

Abstract With more and more data buoys are produced to study the oceans, how to deploy them in a convenient and economic way is very important. In the past, the deployment is often accomplished by large special vessel, which needs a lot of manpower and material resources. Here we introduce a novel deploying method for moored data buoy based on small vessel. This method employs a small vessel with two pulleys(one is served as movable pulley, the other is stable pulley.) and a winch. By way of the relay, it drops all the mooring chain into the water step by step. At last, the anchor is made into ocean water. After several experiments inspection, this anchor-last deploying method for moored data buoy is safe and efficient.

Characterization of Chlorophyll-a over CAL-VAL Site at Kavaratti in the Lakshadweep Sea

Under the Meteorology and Oceanography Programme (MOP) of the Indian Space Research Organization (ISRO), a Calibration-Validation site is planned at Kavaratti in the Lakshadweep Sea with a pair of moored data buoys consisting of fully programmed in situ marine optical observation systems. This will provide an operational capability for vicarious calibration of space-borne ocean color sensors (present and future), algorithm development, and validation of products in case-I waters of the Arabian Sea. For the initial site selection, available ocean color chlorophyll-a concentration were analyzed. The selected deployment site was located between the Kavaratti and Agatti islands of the Lakshadweep Sea.

Moored buoy observations in Arabian Sea warm pool

Time series observations from four moored data buoys in the south eastern Arabian Sea for a period of four months (March - June 2003) are utilized to study the characteristics of warm pool. The moored buoy observations show fair weather conditions in the pre-monsoon period with weak variable winds and calm sea conditions. High SST has been observed during the pre-monsoon warming phase. Surface met observation shows comparatively low-pressure in the region for a period of two weeks starting from the last week of April 2003. Increased wind speed and wave height with a clockwise rotation in wind direction and occasional rains are reported during that period. An interesting observation is the cooling of SST in response to the May 2003 cyclone in Bay of Bengal. Another feature during the warming phase is an oscillation of the order of 14 days observed in SST. Time series observations of salinity in the month of March show the presence of low saline water in the warm pool. A sudden drop of 0.4 psu in surface salinity was observed on 2nd April, which may be due to the advection of low saline plumes in the warm pool region and/or the local pre-monsoon showers. The onset of southwest monsoon and the associated monsoon currents dissipated the warm pool and thereafter the monsoon conditions with high winds, rough sea and frequent rains prevailed in the region.

Calibration and Validation of Remotely Sensed Observations of Ocean Color from a Moored Data Buoy

Abstract Satellite remote sensing of ocean color has the potential to map global surface phytoplankton concentrations at rates of up to once per day, providing wide-area data on a number of fundamental ocean processes relating to biological production, air–sea exchange of biogenic greenhouse gases, climate change, and living resources. There remain a number of problems in the technique, including the possible decline of satellite-sensor sensitivity over time and the difficulty of correcting for light detected by the satellite sensor that originated from the atmosphere. To overcome these problems, the new generation of ocean-color sensors must be coupled with an extensive calibration and validation program. In this study, the authors report on progress to develop a methodology to measure water-leaving radiance and incident irradiance from a moored buoy in order to effect vicarious calibration and validation of ocean-color satellite data at a rate of up to twice daily. The Plymouth Marine Bio-Optical Data B...

Determination of the Influence of Wind on the Keweenaw Current in the Lake Superior Basin as Identified by Advanced Very High Resolution Radiometer (AVHRR) Imagery

The Keweenaw Current is a warm coastal current in Lake Superior that flows northeastward along the northern shore of Michigan's Keweenaw Peninsula. This study focuses on the fate of the current at the tip of the Keweenaw Peninsula. Results of this study suggest that the path of the current beyond the peninsula is primarily controlled by wind. In this study, eleven surface temperature maps derived from Advanced Very High Resolution Radiometric (AVHRR) data using computer assisted image processing techniques were used to identify the Keweenaw Current. Wind data from two moored data buoys, a Coastal Marine Automated Network (CMAN) fixed buoy, and three airport weather stations, collected on the same day as each of the images and for the two days preceding the image date, are used to determine whether wind direction and speed influence the path of the Keweenaw Current past the tip of the peninsula. In nine images the current's path is similar to the surface Ekman transport direction predicted from wind data. All eleven images show a similarity between the current's actual path and a path calculated when net Ekman transport is assumed. Results of this study also show that there may be a possible lag time of one day between a change in wind direction and the current's adjustment to that change.

Data Buoy Aerodynamics

The National Data Buoy Center (NDBC) operates moored data buoys in waters around the United States, providing highly valuable environmental observations in real time from remote marine regions. Key among these observations are wind speed and direction, and, for that purpose, NDBC uses duplicate anemometers on each buoy for reasons of redundancy and data quality. A significant portion of the NDBC buoy array also measures the directional wave spectrum. Buoys so equipped, when also fitted with a fin on the mast, can produce wind speed and direction from the directional wave system output; however, the results, while good, have not been of sufficient accuracy to be of direct use meteorologically. It is postulated that better mast designs could reduce this inaccuracy. Toward that objective, this paper describes an analytical aerodynamic study, employing a custom-written numerical model, of existing and improved buoy mast configurations.

Temporal arrival structure from matched-filter processing of an LFM signal across two convergence zones using Difar sonobuoys.

An experiment conducted near the Nares Abyssal Plain broadcast LFM and cw signals to investigate propagation across two convergence zones (CZ). Air-launched Difar sonobuoys were placed in the first and second CZs simultaneously, and cw bursts of about 1000 Hz, and LFMs covering 900 to 1100 Hz were recorded. A time-delayed echo repeater, which rebroadcast received signals omnidirectionally, was located in the first CZ. These signals were recorded via an expanded videocassette recording system [S. G. Payne, N. R. Bedford, and L. A. Thompson, ‘‘The AEAS Poco Amigo Airborne Acoustic Measurement System,’’ ARL-TR-88-28], which demultiplexes signals from each Difar sonobuoy into its omnidirectional, north–south, and east–west components. Matched-filter processing was applied to these data to obtain a temporal arrival structure. In the case of the second CZ, all three components of the Difar buoy were separately recorded thus allowing horizontal directionality via beamforming. Using calibration information from directional hydrophones, vertical arrival angles were determined [M. B. Bennett, L. A. Thompson, and P. T. Eisman, ‘‘Moored Data Buoy for Shallow Water Acoustic Studies’’ (in preparation)]. The arrival structure of the primary source and the echo repeater will be contrasted. [This work is supported by the ASW Environmental Acoustic Support Program.]