GUIDE TO MOORED BUOYS AND OTHER OCEAN DATA ACQUISITION SYSTEMS by A. Meindl INTERGOVERNMENTAL OCEANOGRAPHIC WORLD METEOROLOGICAL COMMISSION (OF UNESCO) ORGANIZATION DATA BUOY CO-OPERATION PANEL GUIDE TO MOORED BUOYS AND OTHER OCEAN DATA ACQUISITION SYSTEMS DBCP Technical Document No. 8 1996 NOTES The designations employed and the presentation of material in this publication do not imply the expression of any opinion whatsoever on the part of the Secretariats of the Intergovernmental Oceanographic Commission (of UNESCO), and the World Meteorological Organization concerning the legal status of any country, territory, city or area, or of its authorities, or concerning the delimitation of its frontiers or boundaries. Editorial note: This publication is for the greater part an offset reproduction of typescripts submitted by the authors and has been produced without additional revision by the Secretariats. CONTENTS page CONTENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii FOREWORD ..................................................... v 1 . INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 2. MOORED BUOY HISTORICAL OVERVIEW ............................ 4 3. MOORED BUOYS ............................................. 6 3.1 Hulls .•.............................................. 6 3.1.1 Boat shaped ..................................... 7 3.1.2 Toroid ......................................... 7 3.1.3 Bumblebee ...................................... 8 3.1.4 Discus ......................................... 8 3.1.5 Semisubmersible .................................. 9 3.1.6 Other hulls ...................................... 9 3.2 Moorings ............................................. 9 3.2.1 Mooring line .................................... 11 3.2.2 Chain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 3.2.3 Mooring assembly components . . . . . . . . . . . . . . . . . . . . . . . 12 3.2.4 Anchors ...................................... 12 3.3 Electronic payloads ..................................... 13 3.4 Sensors ............................................. 14 3.4.1 Anemometers ................................... 15 3.4.2 Barometers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 3.4.3 Air temperature sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 3.4.4 Sea-surface temperature sensors ..................... 17 3.4.5 Wave sensors ................................... 17 3.4.6 Subsurface sensors ............................... 18 3.4. 7 Other sensors ................................... 20 3. 5 Power systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 3.6 Deployment procedures .................................. 22 3. 7 Refurbishment ........................................ 23 3.8 International buoyage system and other requirements ............. 23 iv page 4. OTHER ODAS .............................................. 24 4. 1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 4.2 Types of station ...............· . . . . . . . . . . . . . . . . . . . . . . . . 24 4.2. 1 Coastal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 4.2.2 Offshore oil rigs ................................. 25 4.2.3 Island stations .................................. 25 4.2.4 Aid-to-Navigation (AtoN) buoys ...................... 25 5. DATA MANAGEMENT ......................................... 26 5. 1 Data flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 5.2 Shoreside processing ................................... 27 5.3 Quality control ........................................ 27 6. CONCLUSIONS I RECOMMENDATIONS ............................. 29 FIGURES .................................................. 31 ANNEXES I. References ........................................... 1-1 II. Member countries' buoy programmes . . . . . . . . . . . . . . . . . . . . . . . 11-1 Ill. List of acronyms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111-1 FOREWORD As noted by the author of this revised guide, E. A. Meindl, in his introduction, accurate marine forecasts (and indeed all meteorological forecasts) depend on a balanced, well-conceived marine observation network to provide data input to numerical models and operational forecasters. Elements of such a network include voluntary observing ships, satellites, radars, drifting and moored buoys and a variety of other ocean data acquisition systems (ODAS), and one of the objectives of the Operational WWW System Evaluation-North Atlantic (OWSE-NA) was to determine an appropriate and cost-effective mix of the different elements for that particular ocean basin. Amongst these various marine observing system components, moored ocean buoys offer perhaps the only means of obtaining real-time, frequent, accurate, long-term observations of meteorological and oceanographic variables from a fixed deep-water location. As well as being invaluable for operational forecasting and the provision of services, such observations are also extremely important for climatological and research purposes. A number of Members have recognized the value of moored ocean data buoys and have already established their own moored buoy programmes, while others are considering initiating such programmes. The Drifting Buoy Co-operation Panel (DBCP), at its second session (Geneva, October 1986), noted that there was a clear requirement for a technical document on the subject of moored buoys, which would both provide essential information for countries wishing to initiate a programme, as well as act as a means for sharing experiences amongst countries already active in the field. The DBCP therefore recommended that a Guide to Moored Buoys and other Ocean Data Acquisition Systems should be considered for preparation along the lines of the existing Guide to Drifting Data Buoys (IOC Manuals and Guides No. 20). This recommendation was endorsed by the fifth session of the Joint IOC/WMO Committee for IGOSS (Paris, November 1988) and taken up by the tenth session of the Commission for Marine Meteorology (CMM) (Paris, February 1989), which nominated Dr G. D. Hamilton (USA) as rapporteur to undertake the preparation of such a guide. This original guide was published by WMO in 1990 as Reports on Marine Science Affairs No. 16 (WMO No. 750). Subsequently, in 1995 the Data Buoy Cooperation Panel considered that this valuable guide should be updated in the light of recent technological developments. Mr E. Meindl (USA) offered to undertake this updating, and the present revised version of the guide while retaining portions of the first edition and including input from Members, is still largely the result of his own work. The sincere thanks of the DBCP, of WMO and IOC, are therefore extended to Mr Meindl for his very important contribution. 1. INTRODUCTION Obtaining adequate marine environmental observations from the ocean areas of the world has long presented a serious problem. Observations of synoptic weather and sea conditions are considered sufficient only along major shipping routes. Marine forecast accuracy will be optimized by a balanced, well-conceived observation network that can provide input to numerical models and operational forecasters. In addition to ship reports, observations in the offshore and coastal areas are provided by satellites, radars, buoys, and other Ocean Data Acquisition Systems (ODAS). Each observing system has strengths and weaknesses, and each tends to complement the others. All of the systems are valuable. Ship observations are absolutely essential to the World Weather Watch (WWW), the World Climate Research Programme (WCRP), and other programmes. However, it is becoming increasingly difficult for individual ships' personnel (whose numbers are decreasing) to maintain meteorological observation schedules. Ship reports tend to be concentrated along shipping lanes, which leads to data-sparse areas outside these routes. The quality of ship observations varies considerably from ship to ship. This is probably caused by differences in individual instrument exposure, sensor maintenance, and differences in the level of training of personnel. Finally, ships tend to avoid areas of rough weather and seas, where observations usually are most needed. Satellite imagery gives an unparalleled, broad view of weather patterns. Its utility, however, is dictated by satellite type and location of the weather with regard to the satellite position. Satellites with all-weather microwave instrument capability and the ability to provide global observations of many marine environmental parameters are becoming operational, but there will still be shortcomings in data coverage and timeliness. Coastal radar is a very useful tool for detecting precipitation and severe weather approaching land. However, its value is limited by range and, in some places, by topography. Drifting buoys have been found to be very effective in improving weather analysis and forecasting in data-sparse marine areas. They have been used extensively in research projects, such as the Tropical Ocean and Global Atmosphere (TOGA) programme. A key component of the World Ocean Circulation Experiment (WOCE), the Surface Velocity Profiler drifting buoy, played a vital role in studies of oceanic circulation. It has been out-fitted with a barometer (SVP-B), making it useful to atmospheric forecasting as well. The use of drifting buoys is documented in a Guide to Drifting Data Buoys [33]. At its second session (Geneva, October 1986), the Drifting Buoy Co-operation Panel recommended that a companion Guide to Moored Buoys and Other Ocean Data Acquisition Systems be considered for preparation. In so doing, it recognized the important role that such platforms play in the acquisition of marine meteorological and oceanographic data and of the potential interest of a large number of countries in their deployment. This recommendation was endorsed by the fifth session of the Joint Intergovernmental Oceanographic Commission (IOC)/World Meteorological Organization (WMO) Committee for the Integrated Global Ocean Services System (IGOSS) (Paris, November 1988) and the tenth session of the WMO Commission for Marine Meteorology (CMM) (Paris, February 1989). As a result, this publication was produced originally in 1990 by Dr G.D. Hamilton (USA). At its eleventh session (Pretoria, October 1995), the Data Buoy Co-operation Panel (DBCP) (formerly the Drifting Buoy Co-operation Panel) recognized the need to update it. -2- WMO and IOC requirements for operational ocean station networks, including moored buoy and other ODAS, are clearly discussed in [4c]. Worldwide requirements are for a minimum of 75 anchored buoys outside the main shipping routes reporting sea-surface and air temperature, surface pressure and other data, four times a day. Establishment of about 10 0 additional conventional tide gauges is needed. Most of the existing requirements for subsurface data to be gathered within the framework of IGOSS come from WCRP requirements for such parameters. A number of Member countries have recognized the need for moored buoys and other ODAS and have established their own programmes. This rapporteur report is intended to inform present operators of the experience of different moored buoy and other ODAS programme managers, as well as to provide information for those planning to initiate such programmes. Moored ocean buoys offer the only means of obtaining real-time, continuous, frequent, and accurate observations of marine conditions from the same deep-water location. Often, the first indications that forecasters have of rapid intensification or change in movement of storms come from buoys. In United States (US) coastal and offshore waters, approximately 50 per cent of all marine advisory warnings or actions are instigated by buoy reports or reports from automated platforms in coastal areas. On 9 November 1983, forecasters were first alerted to the rapid intensification of a storm off the north-west Pacific coast by observations of wind direction, wind speed, and barometric pressure from deep-ocean data buoys. Adequate clues were not initially recognizable from satellite data because this particular storm was at the edge of the useful image. Another severe storm, on 11-12 October 1984, resulted in the drowning of five fishermen and the loss of six vessels off the west coast of Canada. The final Canadian report [ 161 stated that while satellite imagery showed the cloud pattern associated with the storm, it did not give a good indication of its strength or future development. The earliest indication of possible explosive development was from US buoys and two ships that were reporting rapidly falling pressures. Only several hours later did satellite imagery appear to indicate that the storm was changing character. The final report stated that ship reports, while useful, suffer from the fact that ships are moving, are often not positioned to best sample the weather, and provide little information at night. It noted further that "malfunctions and shifts in position of the Geostationary Operational Environmental Satellite (GOES) made it difficult to interpret the early images obtained from the storm". The technical summary of this storm stated that "data from the stationary buoys . .. were absolutely crucial in the determination of explosive deepening", and the report's conclusion endorsed the value of moored data buoys. Canada now has its own moored buoy programme, with a number of buoys deployed in the Pacific and Atlantic Oceans and in the Great Lakes [2, 4f]. The poor observational coverage in the eastern Atlantic at a critical period of rapid development of the low that led to the October '87 storm which devastated parts of southern Britain and northern Europe gave added impetus to the UK Meteorological Office (UKMO) proceeding with its proposals for developing a network of moored buoys in the north-east Atlantic and around its shores; this network was completed in 1995. Buoys also provide ground truth for surface measurements from satellites. Space-based sensors are vulnerable to systematic biases that can only be compensated for by reference to such ground truth [25]. Buoys provide the most accurate data [40] and are being used to develop algorithms for satellite retrieval of winds and other surface parameters. Buoy data are also an important source of observations for research studies, since they are usually the most accurate marine data available and normally one of the few long-time-series data sets from fixed locations. Research programmes on the marine boundary layer, wave generation and propagation, climate, pollution, etc., frequently use buoy data. Numerical model development for forecasting marine parameters uses buoy data