WMO-IOC Data Buoy Cooperation Panel

DBCP Technical Document No. 34

Presentations at the DBCP Scientific and Technical Workshop

Cape Town, Republic of South Africa, 13 October 2008

Abstracts of the presentations
 

The Workshop is organized in sessions that address the following themes:

• Operational Practices and Enhancements – evaluation or analysis of operational performance or trials; data communications and data assimilation; performance and efficiency benchmarking; new systems and practices.
   
• Technological Demands and Developments – demands for enhanced observations collection technology; innovations or developments in related marine observation systems; developments in buoys/instruments (e.g. wave measurements).
   
• Applications of Collected Data – research and operational data applications; case studies.
   
• Special Focus - In addition to the regular themes, this year’s workshop will have a major focus on Marine forecast and services, Numerical Weather Prediction, and coastal risk management. Topics of interest are:

1. Marine forecast – National experience with regard to marine forecast and impact of buoy observations.
2. Numerical Weather Prediction – National experience with regard to NWP and impact of buoy observations.
3. Use of wave information – The use of wave information (in situ observations, satellite products, models) for shipping, port management, and coastal risk management; and the need for in situ observational data for the validation of wave models and satellite wave products, and for specific coastal applications.
4. Data timeliness – Improvement of data timeliness by using specific data distribution systems via national and/or international gateways, existing and new satellite data telecommunication systems and their developments; DBCP drifter Iridium Pilot Project.

• Bill Burnett, NOAA National Data Buoy Center (NDBC), USA
• Johan Stander, South African Weather Service

1.       AOML Data Buoy (ADB) Comparison Study

Author:  Shaun Dolk (AOML), with collaboration from Rick Lumpkin (AOML), Mayra Pazos (AOML), Erik Valdes, Pierre Blouch (Météo-France), Jean Rolland (Météo-France), and Peter Niiler (SIO).

The following concerns are being adressed: (i) deployment Instructions need to be included with every buoy, (ii) variation in packaging (with regard to colored safety tape and colored instructions), and (iii) pull-Pin activation magnet used by one manufacturer

A Bay of Biscay Comparison Study was also made in collaboration with Pierre Blouch and Jean Rolland (Météo France), Peter Niiler, and the three US manufacturers, a subset of buoys has been chosen to carefully evaluate drogue detection. Météo France is able to recover drifters and determine drogue presence in-situ. Drogue detection has proven to be a difficult task, so a closer look at the newly-upgraded strain gauge sensor drifters was arranged. 15 buoys (5 buoys each, from Technocean, Clearwater, and Pacific Gyre) were chosen for deployment in the Bay of Biscay for close evaluation of drogue presence and barometric pressure readings.

A 2009 ADB Comparison Study is planned. SVP drifters from 4 major buoy manufacturers will be selected at random and tested according to GDP standards. Buoy deployments will be made in oceans throughout the world. Various participants will handle and deploy buoys from each manufacturer. Concerns to be adressed include (i) difficulty in assessing drogue presence in some cases, even with tether strain, (ii) variation in packaging (with regard to colored safety tape and instructions), and (iii) some drifters are losing their drogues quickly (6 out of 25 ADB drifters lost drogues within 120 days; 4 of 5 Technocean drifters in Bay of Biscay study after less than one month).

2.       The Restrained ADOS-V:  A lightweight, self-deploying coastal mooring

Abstract:  The ADOS drifter, which has been successfully used to make observations of the upper ocean during hurricanes and the occurrence of large amplitude internal waves, was recently reconfigured into a light-weight, low-cost, coastal mooring to which temperature and pressure sensors are attached every 10 m, together with an Acoustic Doppler Current Profiler. We refer to this instrument as to the “Restrained ADOS-V”.

3.       Operational Deployments of Drifting Buoys into Targeted Tropical Cyclones

Authors:  Peter Niiler (Scripps), Rick Lumpkin (NOAA/AOML), and Luca Centurioni (Scripps)

Abstract:  Under joint sponsorship of NOAA and ONR, we have developed the instrumentation, air-deployment methodology, operational targeting and data codes for GTS fore deployment of drifters in front of targeted tropical cyclones.  SVP-W and SVP-T(z)-W drifters have been deployed in front of Hurricanes in 2005 (Rita), 2007 (Deane) and 2008 (Gustav) with 100% success rate.  This report details the technical advances that have made these deployments successful and the developing technology of subsurface temperature, wind (and wave) observations from drifters.

4.       Development and Testing of NDBC Standard Buoys

Author:  Chung-Chu Teng (National Data Buoy Center, USA)

Abstract U.S. National Weather Service (NWS)/National Data Buoy Center’s (NDBC) Ocean Observing System of Systems (NOOSS) operates three major buoy networks: (1) Meteorological and Ocean Platforms (MOP), (2) Deep-ocean Assessment and Reporting of Tsunamis (DART) buoys, and (3) Tropical Ocean Atmosphere (TAO) buoy array.  These three buoy networks/programs use different types of buoy hulls and systems.  Recently, NDBC developed and designed a Standard Buoy in an attempt to bridge the gap between the three programs by using the same platform for all three applications.

The Standard Buoy uses common parts and form factors and there are a number of “stations” for both sensors and payloads to keep the programs independent.  By using this approach a single platform has the ability to host multiple programs operating simultaneously with minor compromises limited by available “Real Estate”.

NDBC deployed three prototype buoys near Point Conception in Southern California in July 2008.  Each buoy represented one of the three main NDBC programs; MOP, DART, and TAO.  From the analysis of the data collected during their initial evaluation period and some field observations, these three buoys have performed well.  NDBC will continue to test and evaluate the performance and interoperability of the Standard Buoys. 

5.       Partnerships for New GEOSS Applications

Author:  Sidney Thurston (U.S/NOAA)

regional ship time for the deployment of new in-situ ocean observations for IOGOOS/CLIVAR IndOOS Research Moored Array for African-Asian-Australian Monsoon Analysis and

Prediction (RAMA) and other deployments.  By building on and complementing existing capacity building programs, a sustainable capacity for the region is being achieved through the increases in both near real-time in-situ ocean observational data and information as well as demonstrating the more effective applications of existing and new data.  This presentation will provide an updated brief on recent successes, and future plans for the implementation of capacity building and ocean observations for the Indian Ocean and surrounding rim Nations.

6.       Optimizing Buoy Deployments in the South Atlantic to Maximize Benefits for Weather Forecasting

Author:  Shine Lithakazi Mkatshwa (SAWS)

Abstract:  The South African Weather Service makes use of the network of drifting weather buoys in the South Atlantic Ocean in carrying out surface analyses for use in operational forecasting.  The SAWS deploys drifting weather buoys from the SA Agulhas during voyages to Gough Island, Marion Island and the Antarctic continent.  More recently, however, partnerships with “seafaring” institutions have allowed us the opportunity to increase the spatial coverage of the data sparse oceans areas to include those previously out of reach.

Looking at past deployment patterns and analysing drift trajectories over buoy lifetimes will give a clear picture of which sea areas have a tendency to disperse or retain buoys within important ocean areas.  Further to this the presentation will explore those ocean areas that are postulated to have a significant effect on Southern African weather and climate patterns, whether these areas can be effectively monitored by buoy networks and how we can achieve buoy coverage for those areas.  This presentation will encourage the exploration of innovative ways of increasing the coverage of the buoy networks to aid forecasting for the Southern African region.

7.       Drogue-On Sensors:  An Analysis of Existing Sensors and the New Strain Gauge

Author:  Andrew Sybrandy (Pacific Gyre)

Abstract:  Sensors used to indicate a loss fo drogue have been used on drifters since the mid-1980s.  The first drogue-on sensors were a simple salt water switch arrangement.  In the early 1990s, Clearwater Instrumentation and the Scripps Institution of Oceanography developed a sensor utilizing a strain gauge.  Presently, all manufacturers are switching to the strain gauge in order to simplify interpretation of drogue-on status.  This presentation looks at the salt water switch and strain gauge sensors and compares them as drogue-on sensors.

8.       Drifter Performance by Location:  Do Drifters Perform Badly in Specific Areas Around the World?  If So, Why?

Author:  Andrew Sybrandy (Pacific Gyre)

Abstract:  There is plenty of anecdotal evidence concerning poor drifter performance in different areas of the world.  Taking a close look at specific areas shows there are indeed differences.  This presentation looks at a few of those areas and explores how drifters perform in them.

9.       Development and Evaluation of Iridium SVP-B Mini and Other Versions of Drifters

Authors:  T.G. Lunev, S. V Motyzhev and A. G. Krichenko  (Marine Hydrophysical Institute / Marlin-Yug Ltd, Ukraine)

Abstract:  According to the DBCP Workplan for this intersessional period, Marlin-Yug Ltd has been concentrating its efforts to support the evaluation phase of Iridium PP as well as to get some progress with creation of SVP-B drifter, which can be dropped from deck of moving ship with following automatic self-deployment. According to this goal the Iridium SVP-B mini drifter with hourly GPS locations was developed in 2007. The buoy was deployed by SAMS in Drake Strait on December 2, 2007 and it continues to be in operation hitherto. The main results of this experimental buoy evaluation are the followings: modified barometric port provides reliable AP samples for any weather conditions; the buoy has good quality of data sent via Iridium. It has been investigated the reasons of double Iridium sessions and loss of GPS locations when tough weather conditions. Some updating has been done to eliminate these problems for next generation of SVP-B mini drifters produced in this year. This modification of Iridium barometric mini buoys has near 20% more lifetime in contrast with last year buoy. Since this year all the Marlin buoys are equipped with RTC (Real Time Clock) to get for a buoy the GMT synchronization, e.g. for measurements at round hours. Two RTC have been developed: autonomous system with factory installed watch and GPS-RTC, when GMT synchronization can be automatically achieved and supported inside a buoy by means of GPS receiver. The first system can be used for Argos and Iridium buoys without GPS; the second one is intended for drifters with GPS. Experimental clusters of drifters of both kinds were built in 2008 for evaluation of the buoys in-situ. The surface drifter with GSM link (cell phone) and GPS receiver has been developed to study currents in shallow and coastal areas with GSM coverage.

 10.      Buoy Technology Demands, Developments, Operational Challenges and Forecasting Improvements in India

 Authors:  V. Rajendran and G. Latha             (National Institute of Ocean Technology, India)

Abstract:   India being an agricultural based country is heavily dependent on the timeliness and intensity of the monsoon. Systematic time series measurements of meteorological & oceanographic parameters are necessary to improve predictive capability in short term and long term climatic changes.  In order to accomplish systematic collection of met ocean data, the National Data Buoy Programme has been established in 1996 and has come a long way in maintaining the buoy network in Indian seas. This paper presents the buoy technology developments and demands, operational challenges of sustaining the buoys in seas and requirements for improvements in forecasting capabilities.

 After the initial collaboration with Norway for import/deployment of buoys, the NDBP worked on the indigenization of buoy technology and successfully achieved the same in the year 2002. Since then the mechanical/electronic components of buoys are made indigeneously along with the processing data acquisition units.  A 20 buoy network was accomplished in 2004 and a 35 buoy network is achieved in 2008. NDBP is striving to reach the target of 40 buoy network by end of 2008.  In order to cater to different needs, categorized data buoys like Environmental, Port, Wave and Met buoys have been deployed in Bay of Bengal and Arabian seas. The communication link between the buoys and the data reception centre in NIOT through satellite modems have been made, but data gaps due to failure of communication has been a problem area. India has been availing INMARSAT and INSAT is being attempted now.

As for as the demands are concerned, buoy measurements with continuous records over years has been the need and the program has been able to achieve this for a few number of buoy locations. Also denser network of buoys in specific regions has been a demand for particular application areas. 

Buoy data has been used in India for Weather Prediction / Early Cyclone Warning, Ocean State Model Calibration, Climate Research, Satellite Data Validation, Port Development / Navigational Use, Engineering / offshore project and Safety of Life at Sea.

However, the operational challenges in maintaining the buoy network remains to be tackled as these buoys are vulnerable for damage by fishermen community either knowingly or unknowingly.  Though NIOT has conducted awareness campaigns this problem is yet to be solved.

With regard to forecasting systems in India, though buoy data is used for operational forecasts, the accuracy of forecasts still need to improved and to achieve this better modeling capabilities with fine grid data for data assimilation/model calibration and validation need to be looked into.

11.       A First Look at Drifters With Integrated Sonic Anemometers

Author:  Andrew Sybrandy (Pacific Gyre)

Abstract:  Current wind drifters utilize the WOTAN technique to determine wind speed and a magnetic compass and wind vane to measure wind direction.  While the compass and wind vane work well, the WOTAN technique cannot measure the high winds of hurricanes.  While most anemometers cannot be easily mounted on a drifter, newer sonic anemometers may work.  Two drifters outfitted with sonic anemometers were deployed in the northern Santa Barbara channel in August 2008.  This is a presentation of the results of that deployment.

12.       Evaluation of SVP-B Drifters Reporting Through Iridium

Authors:  Pierre Blouch and Jean Rolland (Météo-France)

Abstract:  Météo-France and E-SURFMAR have been actively participating in the DBCP drifter Iridium Pilot Project since its beginning. Eleven SVP-B prototypes fitted with a GPS and an Iridium SBD transmitter (9601) have been deployed since 2006. In addition, 45 SVP-B drifters without GPS were purchased for E-SURFMAR in 2007 for operational purposes. Most of them have been deployed and 80 others were ordered. Out of these, 40 are ready for deployment and the remaining will be delivered to various deployment centers in September.

The raw Iridium data of these buoys are received and processed at Météo-France. Coded into FM18-BUOY - and  FM96-BUFR soon -, they are sent onto the GTS a few minutes after each observation.

The presentation describes the results got from these drifters, including operations and performances. For instance, the recovery and the timeliness of the data, the occurrence of failures, the lifetimes and the observation costs are compared to those got from Argos buoys.

13.       Advances in Operational Wind Wave Prediction Systems at KMA and Their Validation

Authors:  Sangwook Park, Jong Suk Park, Jang-Won Seo and Kum-Lan Kim (Korea Meteorological Administration / National Institute of Meteorological Research)

Abstract:  The operational ocean wind wave prediction at KMA has begun in 1992 as part of numerical weather prediction (NWP) system. The 1st generation wave model was adapted with 80km spatial resolution near Korean peninsular. The 1st major upgrade has been made in 1999 with 3rd generation wave model WAM (WAMDI, 1988) for regional (ReWAM, 0.25°) covering Northeast Asia and extension to global (GoWAM, 1.25°) domain. This upgrade kept pace with the development of NWP system and new installation of supercomputer at KMA. The GDAPS (Global Data Assimilation and Prediction System) T426 and the RDAPS (Regional Data Assimilation and Prediction System) 30km versions provide sea surface wind forecast in corresponding resolution for wave model. In 2005, the 224 GFlops NEC SX5 is replaced by 18 TFlops Cray X1E which is Parallel Vector Processor (PVP) machine with 128 node modules. With this enhancement of computing environment, it becomes feasible expanding the existing operational ocean wind wave prediction system with spatial and spectral resolution increase and optional choice of advanced physical schemes. The new higher resolution regional (ReWW3) and coastal wind wave prediction system (CoWW3) is under operational since March 2008. The mesh size of 1km with 6 encompassing 3° longitude and 2° latitude domains nested inside regional system. The directional wave spectra at boundaries were provided from 1/12° ReWW3. The WAVEWATCH-III code (Tolman, 2002) is adapted for the new ReWW3 and CoWW3 system. The upgrade of global system (GoWW3) with 0.5° resolution is planned for 2009. The sea surface wind and significant wave height are verified routinely in monthly bases. The global moored buoy data including the coastal ones operated by KMA and remote sensing data from Jason retrieval wave height and QuikSCAT retrieval wind data are used for verification of wave prediction system.

14.       Analysis and Modelling of the Upwelling Region of Somali Coast

Authors:  Ali J. Mafimbo and John G. Mungai (Kenya Meteorological Services)

Abstract: During the southwest monsoon two upwelling cells (gyres) are established along the Somali coast, around 4-5⁰N and 10⁰N respectively. The mesoscale structure of the low-level wind field associated with a strong southern upwelling event was investigated. During July 2005 when a strong event occurred, the Somali jet was found to have oscillated at lower frequency of 3-7 weeks and mesoscale winds exhibited high co-variability with prevailing SSTs. Strong values of alongshore winds were observed from late June to mid-July which weakened significantly in the third and fourth week of July. A large off-shore pressure gradient due to differential thermal properties of land and sea was also observed. The results show that prolonged active (break) periods of the jet results in acceleration (deceleration) of alongshore winds. These strong wind stress values during a prolonged active period accelerate the Somali current. The strong alongshore winds result in enhanced Ekman pumping and strong upwelling. In the prolonged break period, the current decelerates, turns east and then southwards. High co-variability of mesoscale winds and SSTs was found in the upwelling zone. To improve understanding of the intra-seasonal to seasonal circulation patterns within the region, the surface circulation of the western Indian Ocean during the summer (JAS) and winter (JFM) monsoon winds was investigated using the Regional Ocean Modelling System (ROMS). The model results suggest a seasonally reversing Somali current with a sub-surface counter current, consistent with observations. The two upwelling cells (gyres) are also apparent in the simulation. The model is applied to better understand the annual cycle of SST, heat fluxes and circulation in the region.

15.      Pilot Project for Wave Measurements from Drifters

Author: David Meldrum (Scottish Association for Marine Science)

Abstract: The presentation reports on the outcome from the JCOMM Technical Workshop on Wave Measurements from Buoys (New york City, USA, 2-3 October 2008), and especially regarding the possibility to make wave measurements from drifters, and follow up developments. A Pilot Project was proposed for the development of Wave Measurements from Drifters (PP-WMD) and the careful evaluation of the proposed technologies. Possible solutions are the use of GPS, or ADCP to estimate the ‘First 5’ (Power spectrum: coefficients as a function of frequency band (S(f)); Directional spectrum: first two pairs of coefficients of spectral moments (a₁, b₁, a₂, b₂)). The Pilot Project will (i) evaluate feasibility of wave measurement from drifters, (ii) explore in particular use of GPS as the cost-effective means of yielding 2-dimensional wave spectra, (iii) prove the technology by measurements and intercomparison with existing trusted wave measurement technologies, (iv) deploy up to 50 wave measurement drifters within the framework of the pilot project, and (v) establish confidence in user community in the validity of wave measurements from drifters. 

16.       Pilot Project for Wave Measurement Test and Evaluation

Author: Val Swail (Environment Canada)

Abstract: The JCOMM Technical Workshop on Wave Measurements from Buoys (New York, 2-3 October 2008) recognized and supported the recent work carried out in the development of the US IOOS Operational Wave Observation Plan (September 2007) and its related documents including the March 2007 US Wave Sensor Technologies Workshop. The underlying basis for that plan, which was endorsed by the NY workshop, made the case that continuous testing and evaluation of wave measurement systems is an essential programme activity, of equal importance to the deployment of new assets. In particular it was agreed that:

• The success of a directional wave measurement network is dependent in large part on reliable and effective instrumentation (e.g. sensors and platforms);

• A thorough and comprehensive understanding of the performance of existing technologies under real-world conditions is currently lacking;

• Independent performance testing of wave instruments is required.

The New York workshop also confirmed the following basic principles:

• The basic foundation for all technology evaluations, is to build community consensus on a performance standard and protocol framework;

• Multiple locations are required to appropriately evaluate the performance of wave measurement systems given the wide spectrum of wave regimes that are of interest;

• Protocols and resources could be established to conduct "in-place" evaluations of wave measurement systems which can not easily be moved to the test sites.

The meeting further agreed that the most effective way to proceed with a DBCP-based Pilot Project on Wave Measurement Test and Evaluation was to expand and extend the relevant parts of the US experience from the IOOS Wave Plan test and evaluation activities to an international context within JCOMM.

17.       WIGOS Pilot Project for JCOMM

Author: Etienne Charpentier (World Meteorological Organization)

Abstract: Following the recommendations from the WMO fifteenth Congress (Cg-XV), WMO has engaged in the integration of marine meteorological and other appropriate observations into the WMO Integrated Global Observing Systems (WIGOS). The WIGOS Pilot Project for JCOMM effectively started with the recommendations from the ad hoc planning meeting that was held in Ostend, Belgium, 29 March 2008.

The deliverables of the WIGOS Pilot Project for JCOMM are (i) developing interoperability arrangements between ocean data systems and the WIS while proving for documented and standardized data, (ii) documenting & integrating best practices and standards, and (iii) Quality Management and implementation of cost effective Quality Management Systems (QMS). The Pilot Project multi-disciplinary approach will permit the provision of consistent, coherent, more timely, and better quality data and products, while at the same time minimizing duplication.

The DBCP was invited to address (i) integrating its Instrument Best Practices into appropriate WMO and IOC Manuals and Guides (e.g. WMO No. 8), (ii) developing Calibration procedures and deployment instructions, (iii) rationalizing Instrument intercomparisons, (iv) assisting in the development of regional marine instrument centre (e.g. NDBC offered to act as such on a trial basis), and (v) developing links with the Association of Hydro-Meteorological Equipment Industry (HMEI) through the buoy manufacturers.

Interoperability with WIS is ensured mainly thanks to the distribution of the buoy data on GTS. RNODC/DB will be working at providing interoperability for the delayed mode data.

18.       Integration of the Argos 3 PMT into an SVP Drifter: Opportunities and Challenges

Author:  Gary Williams (Clearwater Instrumentation, Inc.)

Abstract: The advent of Argos 3 services should mean that the relationship of the SVP drifter to the Argos system is changing in ways that offer the opportunity to improve data collection from drifting buoys. These improvements will affect how ocean observers collect data, the quality of the data and the cost of collecting it. All of these changes are coming, because the PMT and Argos 3 satellites talk to each other exchanging valuable information that can greatly improve the operation of a drifter, as well exchanging data.