Pilot Deployment of a Brazilian Deep-Ocean Buoy [Sea Technology]
(Sea Technology Via Acquire Media NewsEdge) Brazil, U.S. Scientists Collaborate in Testing Ocean Monitoring Platform
In March 2004, the evolution of an extra-tropical cyclone into a tropical system of hurricane strength in the South Atlantic, named Catarina, was confirmed for the first time by satellite imagery (http://earthobservatory.nasa.gov/IOTD/ view.php?id=4369). That storm reached the coast of southern Brazil causing great damage and even some deaths. The timely prediction of its development was hindered by the presumption that the large climatological vertical shear in the atmosphere prevents the formation of tropical storms and by the lack of adequate observations in the ocean, particularly the subsurface layers. In the following years, a proposal for deploying a moored buoy system in the region was endorsed by GCOS (Global Climate Observing System), and in 2009 a project for building an ATLAS-B was approved by Brazilian funding agencies.
The ATLAS-B is a deep-ocean observing platform assembled entirely in Brazil, following theTAO (Tropical Atmosphere Ocean) and PIRATA (Prediction Moored Array for the Tropical Atlantic) ATLAS (Autonomous Temperature Line Acquisition Systems) in its structure, instruments and sampling schemes, but using commercial components. The mooring line was modified to a semitaut line format. The project is being conducted at the Laboratory for Modeling and Observation of the Ocean (LABMON), at the Oceanographic Institute of the University of Sao Paulo, with the technical support of AMBIDADOS (Rio de Janeiro, Brazil) and RDSEA International (St. Pete Beach, Florida).
Holos Brazil Inc. (Rio de Janeiro) fabricates the floating component, made of fiberglass over a foam core, and the aluminum and stainless steel structural frames.
The first prototype of the ATLAS-B, nicknamed "Guariroba," was moored in April 2013 at 28.5° S, 44° W, in the region where Catarina gained the strength of a hurricane. The bottom depth at this location is approximately 3,700 meters. In this application, the surface buoy is equipped with a series of meteorological sensors and is anchored to the sea bottom. The top 700 meters of the mooring line is a 3/8-inch plastic jacketed 3-by-19 wire rope. Oceanographic sensors are clipped to this wire, transmitting data continuously to a Campbell Scientific (Logan, Utah) CR1000 datalogger in the buoy by means of electromagnetic inductive modems. Near the bottom, a sensor with internal storage capacity monitors continuously small variations in pressure, temperature and salinity.
The data collected by the underwater sensors and transmitted via inductive modems are organized in the datalogger and stored in a memory card. A string composed by the data from all sources, including the buoy position, is transmitted daily by means of satellite telemetry. A redundant positioning system was installed in a way totally independent of the buoy's electronics and batteries. The data stored in the deep sensors are retrieved by occasion of recovery and replacement of the whole system.
The Deeper Part of the Mooring Line
The Atlas-B project adopts a semitaut format for the mooring line, with a ratio between the length of the line and the local depth approximately 1.05. Moorings with scopes between 1.0 and approximately 1.1 are generally referred to as "semitaut" designs. The depth in the Cuariroba site is 3,700 meters. Below 700 meters, down to the acoustic release, which is at 50 meters above the seafloor, an 18-millimeter nylon rope was used, in sections of 500 meters length, interconnected with subsurface glass spheres with 17 inches diameter. Right above the pair of acoustic releasers was installed a set of eight glass spheres, for bringing these devices back to the surface upon recovery. The acoustic releasers are connected to the anchor by a 20-millimeter nylon rope and 3 meters of a 5/8-inch steel chain.
Results of the First Deployment
The first mooring was planned as a field test, intended to stay for up to a one-year period, with daily statistics transmitted through Inmarsat. Approximately four weeks after the deployment, data from the Sea-Bird Electronics (Bellevue, Washington) MicroCAT recorder at 300 meters stopped being received. A little more than one month later, the sensor at 500 meters was mute. On September 22, 2013, the entire data transmission was interrupted, except for the tracking system signal, which continued to show that the buoy was still moored at its original position. In late October 2013, though, the tracking system started to show the buoy was adrift and, after an emergency operation, the floating body and the upper 700 meters of the mooring line, with all underwater sensors, were recovered, all in good condition but without the mast and its equipments (meteorological sensors and satellite antenna). There was no sign of vandalism. So, it is most likely that the increased roll of the buoy after being freed caused the mast to break down and the loss of the associated sensors. The bottom part of the line is hopefully still anchored at the original mooring position. The accidental release of the buoy was due to a rupture of the shackles in the junction of the wire and nylon rope, for reasons not yet well understood.
Back to the laboratory, several other problems were identified. It was found that during the first five-month period, six out of 11 subsurface sensors stopped measuring. Both radiometers stopped measuring on August 26, 2013. The datalogger was still recording when read in December 2013. However, all data before October 5, 2013 were lost due to a software issue. There are no meteorological data in the records, other than the data received by satellite. The subsurface sensors records indicate exhausted batteries in all but one of the instruments; the reading of internal memory of the sensors is consistent with exhausted batteries.
The CR1000 has proved a good solution as controller and datalogger. In spite of the short period of the deployment, it seems that power consumption was small enough for longer-term deployment. The CR1000 was serially connected to an Inmarsat satellite modem from Sky wave. This modem integrates a GPS antenna. Data communication worked well and used an operational program developed to get the data from Skywave servers and to create a backup on internal and cloud servers. A dedicated website was developed for data delivery. Another program was developed for QA/QC evaluation, following JCOMM procedures in order to join the WMO's Global Telecommunication System (GTS) network. This required the development of a data template and its codification for binary BUFR format. Final files were uploaded automatically to regional GTS servers in Brazil. Some issues on GTS data handling from the scientific community are on hold since the buoy stopped working before the link to the GTS system was operational. The developed system mimics the fully operational solution offered by the Argos satellite telemetry system, already integrated to GTS. Future work will consider bi-directional data link to the buoy, through Inmarsat and Iridium telemetry, and GTS integration within the buoy electronics.
The Recovered Data
Because of the problems that occurred and the early recovery, the data retrieved from Guariroba was below expectations. However, from the near five-month time series of the daily average received from the surface sensors, the north and south components of the wind, air temperature and humidity, precipitation and atmospheric pressure, and shortand long-wave radiations near the sea surface show intense variability with periods of a few days, and the occurrence of some atmospheric events at longer intervals.
The MicroCATs were clipped to the wire at depths of 1, 25, 50, 75, 100, 125, 150, 200, 250 300 and 500 meters. The two deepest instruments were equipped only with temperature sensors.
After the recovery of the mooring line, it was discovered that, except for the sensor at 25 meters, which was still recording, all the others had completely exhausted batteries.
The deepest sensors, from which the data flow was interrupted before the entire buoy stopped transmission, had the internal recording interrupted at the same time.
In spite of the short period covered in the data recordings, it is possible to observe the signal of the weather system in the daily meteorological data and mesoscale, and the weather and tidal signal in the subsurface oceanographic data.
The ATLAS-B is a pilot experiment, with the long-term goal of it becoming a standard site of the PIRATA Program. As such, it would have been naïve to expect that everything was going to work perfectly. On the contrary, nonanticipated malfunctions were expected. Nevertheless, despite the different problems experienced during the first test, we concluded that the project is on the right track and can be considered a success.
A new deployment is scheduled for the second half of 2014. Presently, intensive efforts are underway to correct the identified weaknesses. Some of the ironware is being changed, the electronics tube and masts redesigned, and the protocols for testing software and batteries improved.
The collaborating authors for this article are: Rick Cole (RDSEA International, USA), Carlos A.S. França (IOUSP, Brazil), Luiz V. Nonnato (IOUSP) and Alberto R. Piola (SHN/ UBA, Argentina). This research activity is conducted in the context of two Brazilian National Institutes of Science and Technology: the INCT-MC and the INCT-Mar-COI, funded by the Brazilian National Council for Scientific and Technological Development (CNPq, Grants 573797/2008-0 and 565062/2010-7) and the Sao Paulo State Foundation for Scientific Research (FAPESP, Grant 2008/5777199). The initiative has also received support from the following projects: ATLAS-B and ATLAS-B2 (CNPQ, Grants 558039/2009-0 and 471717/2013-4); SANSAO (FAPESP, Grant 2008/581019); INCLINE (NAP-USP Mudanças Climáticas); and Inter-American Institute for Global Change (Research Grant CRN2076, U.S. NSF Grant GEO-0452325). The oceanographic cruises are conducted on board the research vessels Alpha-Crucis and Alpha Delphini, purchased with funds from FAPESP. The authors greatly appreciate the support from M. McPhaden and C. Meinig, from PMEL, all engineers and technicians at LIO-USP, LIM-INPE/ CPTEC and AMBIDADOS, and the entire crew of the Alpha-Crucis and Alpha Delphini. *
Celebrating more tfian 50years of serving the gCobaCocean community
Edmo f.D. Campos has a Ph.D. in physical oceanography from the University of Miami. He is a professor and has been head of the Laboratory for Modeling and Observation of the Ocean (LABMON) at the Oceanographic Institute of the University of Sao Paulo, Brazil, since 1990. He is a member of the Brazilian Academy of Science.
Leonardo Barreira has a D.Sc. in ocean engineering and is the head of the Ocean Engineering Croup at the Institute of Sea Studies Admiral Paulo Moreira. He is an officer of the Brazilian Navy, Arraial do Cabo, Rio de laneiro, Brazil.
Francisco Vicentini Neto is a mechanical engineer and welding technologist. He has been a member of the Oceanographic Instrumentation Laboratory (LIO) of the Oceanographic Institute of the University of Sao Paulo, Brazil, since 1984.
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