GUIDE TO OPERATIONAL PROCEDURES FOR THE COLLECTION

AND EXCHANGE OF JCOMM OCEANOGRAPHIC DATA

1999 UNESCO

All nations are profoundly influenced by the world oceans in many ways - some direct and obvious, others indirect and subtler. Even those countries without ocean coastline feel the influence of the ocean, for example, as it affects world-wide weather and climate and in the availability of foreign goods and access to distant markets. Some influences of the ocean are beneficial; others may be detrimental to human activities; most are beyond our ability to control, except in very limited ways. Forewarned with knowledge of the state of the ocean and even a limited prediction of future trends, it may be possible to maximise the beneficial effects and to avoid or guard effectively against those that could be detrimental.

The Integrated Global Ocean Services System (IGOSS) was conceived as a means to collect and exchange oceanic data in such a form that they could be readily interpreted and applied to practical problems. Data in various forms may be gathered from many sources. It is necessary to properly encode and route these data to processing centres using proper quality control procedures. It is possible to prepare products that summarise and/or interpret the data in ways that are meaningful and useful to others. Finally, the products are distributed to users and the data are stored or "archived" for future use. The IGOSS system had been designed to carry out these functions in co-operation with other international agencies.

The Global Ocean Observing System, GOOS, is a new international system for making ocean observations and providing both data and information to clients. It is setting requirements for the type and frequency of sampling, for timely delivery of data to users and establishing the data quality needs. In co-operation with the Global Climate Observing System (GCOS), GOOS has already developed a first action plan for data requirements and exchange entitled: "Global Physical Ocean Observations for GOOS/GCOS: an Action Plan for Existing Bodies and Mechanisms. IGOSS was one of the bodies concerned and had an important role to play for GOOS to provide data and information and to respond positively to the requirements expressed.

In the mean time, GOOS, GCOS and the World Climate Research Programme (WCRP) expressed the requirement for a coherent joint IOC-WMO mechanism for the implementation and international co-ordination of operational oceanography. On that ground, as well as from a number of related considerations (e.g.: the need for a fully co-ordinated mechanism for implementing the requirements for ocean and surface marine meteorological data in support of GOOS and GCOS; the expanding requirements of all marine users for a comprehensive range of marine meteorological data and products; etc.), the IOC and WMO governing bodies decided to establish a Joint WMO-IOC Technical Commission for Oceanography and Marine Meteorology (JCOMM), to replace the existing Joint IOC-WMO IGOSS and the WMO Commission for Marine Meteorology (CMM). JCOMM shall be responsible for: the further development of the observing networks; the implementation of data management systems; the delivery of products and services; the provision of capacity building to Member States; and the assistance in the documentation and management of the data in international systems. The JCOMM terms of reference encompass, inter alia, the programme activities previously undertaken within IGOSS.

Within that general framework, this document is intended as a general guide to the operational procedures for the collection, encoding, quality control and exchange of oceanic surface and sub-surface temperature, salinity and current (BATHY, TESAC and TRACKOB) data. It is anticipated that individual nations will issue specific guidelines within the framework of this document. In all cases, it should be recalled that the overall objectives of JCOMM include the timely collection and exchange of oceanographic data and products. Therefore, proper procedures and precautions must be exercised at all times by participants in the programme.

This edition of the Manuals and Guides No. 3 replaces the 1988 edition.

1.1 GENERAL

1.1.1 The Joint WMO-IOC Technical Commission for Oceanography and Marine Meteorology (JCOMM) is the body responsible for, inter alia, the implementation and international co-ordination of operational oceanography. It encompasses the late WMO Commission for Marine Meteorology (CMM) and Joint IOC-WMO Integrated Global Ocean Services System (IGOSS). The latter used to be the international operational oceanic system for: (i) the global collection and exchange of oceanic data; and (ii) the timely preparation and dissemination of oceanic products and services. WMO and IOC co-operate in the planning and implementation of JCOMM. The operation of JCOMM is based on national contributions and depends on the full support of all IOC Member States and WMO Members. The timely dissemination of data and/or products depends on the facilities of the Global Telecommunication System (GTS) of the World Weather Watch (WWW) of WMO.

1.1.2 The programme for the collection and exchange of BATHY and TESAC data was initiated as a pilot project on 15 January 1972 and became fully operational in June 1975 as the BATHY/TESAC Operational Programme. It involves the global collection and exchange of ocean temperature, salinity and current data observed from merchant ships, research vessels, Ocean Weather Stations (OWS), ocean data buoys, offshore platforms, coastal stations and aircraft, and other platforms. The incorporation of new technological developments will enhance the implementation of this programme.

1.1.3 The development of the Global Ocean Observing System, GOOS, relies heavily on the infrastructure developed by JCOMM both for data collection and data exchange. GOOS is conceived as a new, internationally organized system for gathering, coordination, quality control and distribution of many types of marine and oceanographic data and derived products. The climate module of GOOS has as one goal the provision of observations needed for the prediction of climate variability and change. Thus GOOS is setting the requirements for data collection and dissemination to which the JCOMM programme is responding.

1.1.4 This Guide describes the operational procedures for the BATHY/TESAC Operational Programme, which includes the collection and exchange of operational BATHY, TESAC and, since 1 November 1987, TRACKOB data. The instructions and guidelines to be followed are arranged under the following main headings:

• Data Collection
• Data Encoding
• Data Routing
• Error Checking and Quality Control
• Monitoring

1.2 DEFINITION OF TERMS

A number of terms are used in this Guide with a meaning unique to JCOMM (oceanography) and may cause some confusion to meteorologists, oceanographers and data specialists. Working definitions of these terms, taken from the IGOSS Glossary, are given below.

Operational Data

1.2.1 Oceanographic data up to 30 days old from the time of observation. Operational data should be exchanged on the GTS.

Non-Operational Data

1.2.2 Oceanographic data older than 30 days. Non-operational or delayed mode data should not be exchanged on the GTS.

Timely

1.2.3 Within that space of time, since the time of observation, such that the data continue to be representative of the environmental conditions and are of operational use. The duration of the timely period depends on the physical phenomenon under consideration. For JCOMM (oceanography) purposes that duration goes from one or two days up to 30 days.

Oceanographic Product

1.2.4 Any analysis, forecast or summary of oceanographic conditions prepared and disseminated in a format, and according to a schedule, that suits the needs of governmental, commercial, academic or private user groups. JCOMM (oceanography) service products include analyses, forecasts and summaries for such variables as sea surface temperatures, sub-surface temperatures, mixed layer depth, ocean frontal position, current, salinity and their anomalies.

Operational Product

1.2.5 An operational product is prepared to reach the user in a timely fashion and is produced on a regular basis for more than a year. An operational product distributed by means other than through telecommunications channels is referred to as a delayed mode product.

Report

1.2.6 An observation encoded in appropriate code form and transmitted to shore (BATHY reports are in WMO code form FM 63-X Ext., TESAC reports in WMO code form FM 64-IX, and TRACKOB reports in WMO code form FM 62-VIII Ext.). Reports are then forwarded through national channels to a GTS input point where they are gathered into GTS bulletins.

1.2.7 A message transmitted from the platform to shore and containing:

(i) the abbreviation OBS;

(ii) the radio address of a meteorological or oceanographic centre;

(iii) one or more reports;

(iv) any other information prescribed by radio-telecommunication procedures.

2.1 VARIABLES INVOLVED

2.1.1 The primary variables to be observed within the framework of JCOMM (oceanography) are those which are relevant for the physical description of the state of the ocean and which can be measured on a routine basis. Therefore, the Operational Programme deals with temperature, salinity and currents. In addition, other environmental variables may be useful in order to interpret the data.

Temperature

2.1.2 Knowledge of the thermal structure of the upper layers of the ocean is essential in order to understand heat transfer between the atmosphere and the sea, and heat transport in the ocean. In addition, knowledge of the thermal structure is needed for operational applications (e.g. in fisheries) and for climate analysis.

Salinity

2.1.3 Sea surface salinity is important in order to determine water mass movement, circulation and frontal activity. Sub-surface salinity structure together with sub-surface temperature structure is useful for calculating geostrophic currents. It is also pertinent to the behaviour of the mixed layer.

Currents

2.1.4 Currents are the main process through which heat is transferred from one zone of the world to another, and is a critical item in climate studies. Regular current monitoring is also of great value for such practical purposes as ship routing.

2.2 INSTRUMENTATION

The instruments used for measuring temperature, salinity and current are:

2.2.1 For temperature versus depth:

• Mechanical Bathythermographs (MBT)
• Expendable Bathythermographs (XBT)
• Airborne Expendable Bathythermographs (AXBT)
• Submarine launched XBTs (SXBT)
• Thermistor Chains
• Reversing Thermometers.

2.2.2 For temperature and salinity versus depth:

• Hydrocasts
• Conductivity-Temperature-Depth Instruments (CTD)
• Expendable CTD (XCTD).
• PALACE floats (Profiling Autonomous Lagrangian Circulation Explorer) or profiling floats.

2.2.3 For surface temperature and/or salinity along a ship's track:

• Any of the above
• Different kinds of instruments fixed to the hull of a platform such as thermo-salinographs.

2.2.4 For sea surface current:

• GEK (Geomagnetic Electrokinetograph)
• Acoustic Doppler Devices
• Ship's set and drift
• Drifting buoys.

2.2.5 For current versus depth:

• Moored current meters
• Doppler current profiling systems.

2.3 PLATFORMS

Ships

2.3.1 Ships are a valuable means of oceanographic data gathering. Three types of ships are commonly used for this purpose:

1. Merchant ships are of major importance for JCOMM and are encouraged to observe oceanic variables by participating in the IOC-WMO Ship-of-Opportunity Programme (SOOP) and in the WMO Voluntary Observing Ships (VOS) scheme;
2. Research vessels continue to be a prime element for JCOMM (oceanography) because of the versatility, dependability and accuracy of their observations and despite the fact that their number is relatively small and their operating costs are increasing;
3. Ocean Station Vessels (OSV) assigned to the Ocean Weather Stations (OWS) have provided high quality time-series measurements of oceanographic variables at fixed points, and are important for the calibration and verification of satellite and ship data.

Buoys

2.3.2 Both moored and drifting buoys have proved to be useful for oceanic data gathering. Member States should make particular efforts to develop reliable automatic systems capable of producing information on sub-surface variables in the ocean environment.

2.3.3 Aircraft are used for the airborne deployment of such instruments as expendable bathythermographs and for the recording of measurements.

2.3.4 Coastal stations and offshore platforms should be considered part of JCOMM (oceanography) as far as they provide JCOMM oceanographic data. In particular, countries and/or firms operating offshore platforms are encouraged to carry out regular measurements of oceanic variables in order to provide calibration values and dependable time-series.

2.3.5 Newer platforms, such as Profiling Autonomous Lagrangian Circulation Explorer (PALACE) floats are a technology that shows great promise to make remote observations in ocean regions not easily or regularly visited by other platforms.

2.4 OBSERVATIONAL STRATEGY

2.4.1 Three scales of interest determine the requirements for observations by JCOMM (oceanography):

1. The largest of these scales is the ocean basin scale wherein observations are needed to investigate or describe large, planetary-type or climate phenomena or motions occurring in ocean basins;
2. Regional requirements are directly linked to more detailed investigation of planetary motions and the preparation of corresponding products. These requirements will arise from cooperative regional programmes by two or more participating Member States;
3. Finally, there are requirements on national or local scale that are dictated by the scientific, economic and industrial requirements of the individual state. These requirements will vary greatly from country to country, and will undoubtedly interact with the other 2 categories.

2.4.2 The frequency and spacing of observations under JCOMM (oceanography) must be adjusted to suit the physical scales of the oceanographic phenomena to be described. The following classification of scales of oceanographic phenomena are considered under JCOMM:

Although the scales indicate the minimum sampling rates to describe the process, higher sampling rates in space and time may be required to prevent aliasing. In general terms, fixed stations such as weather ships, moored buoys, etc., should take observations at least four times per day. It is desirable that mobile ships take BATHY or TESAC measurements at least 4 times per day as well, or at approximately 100 km intervals (more closely spaced if crossing major current systems or crossing the continental shelves). TRACKOB observations should be made at shorter intervals, e.g., every one or two hours. The operating agency or institution should determine more precise specification of observational programmes. Apart from the requirement for a world-wide distribution of oceanographic data, there is a strong demand for repeated data from the same area through seasonal or annual cycles. Repeated sections can be achieved, for example, by means of merchant ships on routine tracks.

3.1 The encoding instructions are designed to provide a means for formatting the report as a ship-to-shore message. Detailed instructions on how to complete the BATHY, TESAC and TRACKOB code forms are contained in Annex II, III and IV, respectively.

3.2 It has been demonstrated (see Hanawa, et. al., UNESCO Technical Papers in Marine Sciences, 67, 1994) that expendable instruments such as XBTs do not fall through the water column at the rate specified by the manufacturer. This has an impact on the computed depths of observations. The present real-time BATHY code form has a group, IXIXIXXRXR, to encode the fall rate equation used when reporting data in real-time. A new TESAC code form will be instituted in 2000 to contain the same information for XCTDs. It is essential that this information is included in the real-time data.

3.3 More commonly, information to create a BATHY, TESAC or TRACKOB message is stored digitally and prepared in the correct format for transmission via satellite to shore. The full resolution profile or higher time resolution surface observations are recorded on magnetic media by a computer. The recorded data are often subsampled to create the BATHY, TESAC or TRACKOB message and these are sent ashore. When the platform returns to port, the magnetic media with the full resolution data should be forwarded to the country's NODC or other agency willing to handle the data.

3.4 For some platforms, such as PALACE floats, the full resolution data are sent ashore via satellite. This is because these platforms are expendable. At the shore processing facilities, BATHY or TESAC reports are created from the profiles. The profiles may or may not be subsampled.

3.5 There are two strategies used in subsampling a profile to prepare a BATHY or TESAC report. The first strategy chooses observations at a predetermined set of depths. This is encoded in the BATHY or TESAC as "selected depths". The second strategy chooses observations at inflection points in the profile. This method is better able to represent the shape of the profile and is encoded in the BATHY or TESAC as "significant depths".

3.6 Even though profile data may be recorded digitally, a form that records basic information about each instrument deployment is valuable. The record should include information about the ship, its location and, sometimes, other observations made at the same time. Annex I shows a suggested form for the log. Copies of these forms should be sent along with the delayed mode data to the appropriate processing centre.

4.1 GENERAL DATA FLOW

4.1.1 JCOMM oceanographic data that do not need subsequent processing (such as is required to decode a satellite transmission) enter the dissemination system in two ways:

1. As operational messages received at a National Oceanographic Centre (NOC) or a National Meteorological Centre (NMC) and a Regional Telecommunication Hub (RTH). In the past, these arrived via coastal radio stations, but now more frequently are received via email or ftp (file transfer protocol) using the Internet; and
2. As completed reports, or raw data, and log forms via a national oceanographic agency through the normal International Oceanographic Data and Information Exchange (IODE) procedures.

4.1.2 Data that need some subsequent processing, such as data from environmental satellites and satellite-communicated data from moored and drifting buoys, bottom moorings and floats, pass through and are processed by satellite receiving centers. The processed data then enter the system in two ways:

1. As operational data via a NOC or NMC and a RTH;
2. As non-operational data with all available additional information - delivered on computer media - via National Oceanographic Data Centres (NODCs) through the data exchange system of IODE.

4.1.3 To provide the data to the user within the operational time, as well as to provide long-time archiving, the data flow is separated into two components as the figure next page shows:

1. An operational data flow for which JCOMM is responsible. This data flow contains, in general, that information which has been transmitted. The time frame in which the data set is available for JCOMM activities extends from one to thirty days. The quality control procedures applied to these data are described in Section 5. The operational data set is also forwarded to the RNODCs (JCOMM) of IODE which provide long-term storage; and
2. A non-operational data flow for which IODE is responsible. This data flow contains detailed identification information and ocher supporting environmental data as well as the basic oceanographic data.

4.1.4 Bridging these two systems is the Global Temperature Salinity Profile Programme, GTSPP. This programme was started in order to improve the performance of both (then) IGOSS and IODE in making data or higher quality more quickly available to users. GTSPP handles temperature and salinity profile data as well as other types of profiles collected at the same time. The real-time (JCOMM) data are gathered from the GTS and pass through well-documented quality control and duplicates checking procedures. The data then pass to a Continuously Managed Database, CMD, from which users have access to the most up-to-date and highest quality data available at any time. As delayed mode data arrive at the CMD they replace the lower resolution real-time data. On a regular basis, the available data are passed to Science Centres who subject the data to higher data quality assessment and return them to the CMD.

4.1.5 There are three Science Centres that participate in the GTSPP. They are at Scripps Institution of Oceanography in San Diego, the Atlantic Oceanographic and Meteorological Laboratory in Miami, and CSIRO in Hobart. They use custom software to examine the data and assess their scientific quality. Flags are assigned that provide reasons for judging the data to be of lower quality. Data are processed yearly with as much delayed mode data as possible replacing the real-time data. The resulting files are then passed back to the CMD, for archiving.

4.1.6 The collection and exchange of operational JCOMM oceanographic data involves the following four stages:

• Platform to Shore Transmission
• National Routing Arrangements
• International Routing Arrangements
• Operational Data Dissemination.

4.2 PLATFORM TO SHORE TRANSMISSION

4.2.1 The platform to shore transmission concerns the forwarding of data from the platform to a National Oceanographic Centre (NOC) or a National Meteorological Centre (NMC) via a shore-collecting centre. At the present time, this transmission is largely based on satellite data collection systems although some data may still be collected through the International Maritime Mobile Service (IMMS).

4.2.2 The report consists of the completed BATHY, TESAC or TRACKOB code form. In most cases, these reports are prepared by computer software from the digitally stored data. After checking, the data are sent ashore through satellite communications services.

4.2.3 The reports should be transmitted as soon as possible after the time of observation. However, the reports may be transmitted up to 48 hours after the time of observation, in case operational difficulties preclude their earlier transmission. Nevertheless, in order not to interfere with the transmission of meteorological reports, it is recommended to avoid, as far as possible, the following regularly scheduled meteorological transmission periods:

4.2.4 Many reports which were not telecommunicated may be collected after the return of the ship to port. The operators are encouraged to forward the data to the appropriate national agency as soon as practicable for insertion onto the GTS. As long as the data are less than 30 days old, they may be inserted on the GTS. If data are older than this, they may be forwarded to any data centre participating in the GTSPP. In particular, the Marine Environmental Data Service of Canada (MEDS, 12th floor, 200 Kent Street, Ottawa, Ontario, Canada, K1A 0E6.

See also http://www.meds-sdmm.dfo-mpo.gc.ca or email services@meds-sdmm.dfo-mpo.gc.ca) handles the real-time component of the GTSPP and so it is appropriate to send such data to them for inclusion in the international data bases. These data are still very valuable for a number of purposes.

4.2.5 The use of semi-automated or automated transmission devices onboard platforms is common. These include those employed in the International Maritime Satellite (INMARSAT) system, environmental satellite DCPs and the Argos System. Specific procedures for data transmission are determined by the particular system in use. In all cases, the objective remains to transfer observational data from the platform to the appropriate NMC or NOC for insertion onto the GTS as rapidly and as error-free as possible.

4.3 NATIONAL ROUTING ARRANGEMENTS

4.3.1 The national arrangements for the routing of JCOMM oceanographic observations fall under the responsibility of the country in which the shore-collecting station is located. In principle, this part of the routing can be envisioned as follows:

4.3.2 The messages sent from platform to shore contain the address of the NMC or NOC to which they are to be forwarded from the shore collecting station. If the NOC and the NMC are not co-located, the NOC should ensure the relay of reports to the NMC.

4.3.3 The NMC is usually responsible for the collection of oceanographic reports received by centres located in its area of responsibility and for their transmission to the associated RTH of the GTS. The NMC is also responsible for checking and correcting reports to ensure that standard telecommunication procedures are applied. The NMC acts therefore as the GTS centre responsible for compiling individual reports into bulletins. It is recommended that bulletins be compiled at least every 12 hours or as they become available. They may contain reports from several ships and various observation times. BATHY, TESAC and TRACKOB observations should be compiled in separate bulletins.

4.3.4 WMO Members operating those GTS centres which insert oceanographic reports onto the GTS should provide the WMO Secretariat with the transmission schedules, TTA1A2ii and CCCC groups.

4.4 INTERNATIONAL ROUTING ARRANGEMENTS

4.4.1 The exchange programme of JCOMM oceanographic observations over the GTS is based on the decision of the WMO Executive Council and Commission for Basic Systems (CBS) that the WMO Regional Associations make suitable arrangements for the exchange of these data in their regions. It has, however, become necessary to widen the scope to include inter-regional and global exchanges, taking into account the increasing requirements for the exchange of oceanographic data.

4.4.2 On the basis of requirements expressed by Members, the WMO Secretariat has prepared a plan for the routing of the JCOMM oceanographic messages. The basic principles followed in establishing this plan were:

1. These messages are exchanged globally on the Main Telecommunication Network (MTN) and its branches. Since the MTN and its branches are fully operational, all WMCs and RTHs located on the MTN and its branches receive and transmit messages in accordance with stated requirements;
2. The WMO standard telecommunication procedures specified in the Manual on the Global Telecommunication System (WMO No. 386) apply to JCOMM oceanographic messages;
3. The national meteorological services operating NMCs as GTS centres are the responsible parties for the international exchange of the messages.

4.4.3 Only messages formatted in accordance with the rules enacted in the Manual on the GTS may be routed on the GTS:

1. Each message is composed of a starting signal <SOH>, one bulletin and an end-of-message signal, <ETX>;
2. A bulletin is composed of an abbreviated heading followed by a set of reports in one code form only, each separated by a report separation signal;
3. The reports have already been defined (see para. 1.2.6).

Annex V shows the layout of a JCOMM oceanographic message as it must be compiled for exchange through the GTS. Annex VI gives an example of such a message and explains how to decode it.

4.5 OPERATIONAL DATA DISSEMINATION

4.5.1 The NMC which is the terminal point of the GTS for the receipt of data disseminated over the GTS is responsible for receiving the oceanographic reports and forwarding them to oceanographic and meteorological centres involved in the preparation of products. The routing arrangements in this phase should be established on a national basis.

4.5.2 Requirements for the operational receipt of oceanographic data should be directed to and consolidated by the National Meteorological Service which operates the NMC as a GTS centre. These requirements are to be further submitted to the WMO Secretariat to ensure the co-ordination of routing arrangements, in consultation with appropriate WMO bodies, for the implementation by Members concerned.

4.6 NON-OPERATIONAL ROUTING ARRANGEMENTS

4.6.1 The international data exchange and archiving of JCOMM oceanographic data in non-real-time falls under the responsibility of the International Oceanographic Data and Information Exchange (IODE) system of IOC. The Guide to IGOSS Data Archiving and Exchange (IOC Manuals and Guides No. 1) stipulates the procedures to be followed. As the original data records and the log forms are to be submitted, observers should strive to label records correctly.

4.6.2 After return to port, the completed log forms and data logged on magnetic media will be forwarded to the national oceanographic agency in charge of collecting these data. The actual channels through which the data are routed before entering the IODE system vary from country to country.

5.1 INTRODUCTION

5.1.1 The value of JCOMM oceanographic data for a user depends essentially upon the quality of the data. In this context, quality is meant in terms of accuracy and reliability which concerns the physical content of a measurement as well as in terms of correct encoding of the value measured.

5.1.2 Several studies have shown that a significant percentage of the reports still contain errors that can be easily corrected. These errors are the ones that are possible to detect by examination of a telecommunicated data set without the benefit of the original data. Thus, such subtle errors as those arising from minor instrument malfunctions or miscalibration, poor choices of inflection points by the observer, or inaccurate reading techniques are not considered in this classification. The following are definitions of different types of errors, taken from the IGOSS Glossary, which will be used in this text.

5.1.3 An error which concerns the starting line of a message, the abbreviated heading of a bulletin or end-of-message signals.

5.1.4 An error which is assumed to have occurred if the report received does not conform with the internationally agreed code forms FM 63-X Ext. BATHY, FM 64-IX TESAC or FM 62-VIII Ext. TRACKOB. This can be an error in the position or content of those fields or characters which are used to indicate the type, origin and content of the report.

5.1.5 An error in the reported value of any observation, e.g., date/time of observation, position, depth, temperature, salinity, current and wind speed and direction, air temperature and pressure.

5.1.6 At any stage within the data exchange scheme, errors may creep into a report, therefore quality control procedures should be applied to the JCOMM oceanographic data at the following three stages:

• Onboard ship,
• At a NMC (or NOC) before insertion onto the GTS,
• At a SOC (or NOC) after reception from the GTS.

5.2 STEPS TO IMPROVE THE DATA QUALITY AT ITS ORIGIN

5.2.1 Errors begin with the instrumentation. The accuracy of the instrument, its calibration and the operational limitations, e.g. depth or the speed of the ship, have to be considered. In this context, reference is made to the Guide to Oceanographic and Marine Meteorological instruments and Observing Practices (IOC Manuals and Guides Series No. 4).

5.2.2 Crude or subtle errors introduced by such factors as malfunctioning temperature thermistors, recorder response and uncalibrated thermometers are very often difficult to detect from isolated stations. Also, the spike induced by insulation punctures along the launcher probe connecting wire sometimes looks real. The recording of additional information, such as sea surface temperature, from other sensors can help significantly to identify such problems (See Annex I).

5.2.3 The proper training in the use and maintenance of ocean instrumentation, particularly the instrumentation used onboard ships-of-opportunity, is an important factor in the improvement of data quality.

5.2.4 Direct discussion of the programme between the ship's crew and a national authority will lead to closer identification with the value and importance of the JCOMM programme. Feedback of results and expressions of appreciation are some of the best means of ensuring high-quality reports from the observing ship.

5.2.5 Several types of automated systems have been developed. These systems automatically format and transmit data through highly reliable satellite systems. Therefore, they are undoubtedly the best way to minimize data quality problems arising from manual interpretation, coding and transmission.

5.2.6 One such system, the Shipboard Environmental Data Acquisition System (SEAS) was developed in the USA to deliver data from ships to shore. Data entered into the SEAS units are automatically transmitted through the GOES or INMARSAT-C satellite systems or by email. As the data pass to US processing facilities, they are also made available to authorized users who have a terminal with a phone modem. Only seconds elapse between the time of shipboard transmission and the arrival of the data to users. The SEAS equipment is totally portable, can be set up in a few hours and occupies a space of about 0.3 m³. Currently, it is possible to enter, code and transmit standard shipboard meteorological observations (winds, temperature, pressure, waves/swell and ice) and Expendable Bathythermograph (XBT) observations via SEAS.

5.2.7 Another automated system was developed by Collecte Localisation Satellite (CLS) Service Argos at the request of the Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER) to gather, record, process and transmit BATHY data to the GTS via the Argos system. The hardware is made up of a launcher, an electronics unit and a microcomputer (which can be used for other shipboard applications when not required for soundings). The electronics unit is portable, and occupies less than 0.1 m³. The location of the observation is computed at the Argos processing centres in Toulouse, France, or Landover, USA, which also forward the reports to the RTHs of Paris or Washington, respectively, for insertion onto the GTS.

5.3 QUALITY CONTROL PROCEDURES BEFORE INSERTION ONTO THE GTS

5.3.1 JCOMM oceanographic reports are inserted onto the GTS by NMCs or, as an exception, by NOCs which have access to the GTS via an NMC. The data arriving at NMCs contain various errors, some of which are easily detected and identified and, therefore, can be corrected, such as, for example, primarily coding errors. The data reside at NMCs for only a short time, so that correction procedures are best carried out operationally on a computer. However, limited manual corrections can be carried out where data quantity is not large. It is therefore recommended that the minimum set of correction procedures intended for this purpose (see Annex VII) be applied to the reports at an NMC (or at an NOC on behalf of an NMC) before the data are inserted onto the GTS.

5.3.2 When compiling bulletins and preparing messages, special attention should be given to the following message format errors which are frequently observed (see Annex V):

1. TT must be SO. If it is not, most centres cannot retrieve the bulletin and it will be lost.
2. A₁A₂ are incorrect. ("Country codes" (WMO No. 386, Vol. 1, Part 11, Attachment II-6, table C1)) should not be used; table C2 (same reference) should be followed). The position of the observation is not within the region designated by A₂; whenever practicable, X should not be used for A₂;
3. ii conflicts with C in catalogue number. For JCOMM oceanographic data bulletins, ii should be in the range 01-19 inclusive for global distribution according to the Manual on GTS (WMO No. 386, Vol. I, Part II, para. 2.3.2.2);
4. YYGGgg is incorrect. This should be the time (day, hour, minute in UTC) that the bulletin is compiled at the GTS centre for exchange;
5. BBB used incorrectly. The use of RTD is reserved for delayed information but has been used for overflow bulletins at the same time as the normal bulletin.

5.4 QUALITY CONTROL PROCEDURES AFTER RECEPTION FROM GTS

5.4.1 The further quality control of JCOMM oceanographic data is necessary after reception of the message from the GTS to ensure the accuracy of operational products and to provide archive centres with uniform quality-controlled data sets.

5.4.2 Quality control procedures at this point in the system should include checks for message format, coding and physical errors. Data which are found to be erroneous or highly suspect should be flagged as such. Changes are permissible only when they can be made with a high degree of confidence and if the original value is stored in the data record. No data should be removed from the record. Flags are to be provided for all reported physical variables including position, date, time and depth. The flags are considered necessary to provide users with information and results of quality control operations and to document any changes made to physical variables.

5.4.3 The GTSPP has published a well-documented set of quality control procedures in IOC Manuals and Guides No. 22. This has been further enhanced by procedures published by the participating Science Centres in GTSPP. These latter are available from the separate centres (CSIRO, Australia, AOML and Scripps in the U.S.A.) or through data centres participating in the GTSPP. It is recommended that these procedures be used.

6.1 GENERAL

The exchange of JCOMM oceanographic reports is monitored in four ways. Exchange of national data is monitored at the national level. International exchange is monitored on a broad statistical basis through examination of monthly input/output figures submitted by Members. Finally, detailed examination of the GTS exchange is periodically carried out in conjunction with other GTS monitoring within the World Weather Watch of WMO. Finally, there have been extensive monitoring procedures established by the GTSPP.

6.2 NATIONAL MONITORING

Since reports come from a variety of platforms without fixed positions or observation times, it is important that a close watch be maintained on the entire process of exchange to avoid interruptions in data flow due to errors in formatting or routing. It is a national responsibility to assure that all observations destined for international exchange are collected, correctly formatted and exchanged via the GTS in a timely manner. This can only be accomplished through an adequate national monitoring programme. In particular, it is important that the national monitoring programme know how many messages are sent from their ships and to check that all of these appeared on the GTS.

6.3 MONTHLY EXCHANGE

The monthly summaries of the number of JCOMM oceanographic reports inserted onto the GTS (INPUT) and extracted from the GTS (OUTPUT) are submitted by national meteorological or oceanographic centres to the SOOP Technical Coordinator. An example of the monthly statistical summary with an explanation for completion is given in Annex VIII. These summaries are analyzed to identify data exchange problems, particularly inconsistencies among centres. The centre where the apparent problem occurs is then alerted to the nature of the problem and a solution is sought.

6.4 PERIODIC GTS MONITORING

The periodic GTS monitoring is used to determine the efficiency of the exchange of the JCOMM oceanographic data and to identify discrepancies observed at different centres. The actual message transcripts at several centres are compared. One of the major causes of data loss is errors in formatting the GTS messages.

6.5 GTSPP MONITORING

6.5.1 A number of reports are generated from the GTSPP to monitor data flow and quality. The real-time data are accumulated on a monthly basis from four different centres connecting to the GTS (Canada, U.S.A., Japan and Germany). These are examined to determine how many reports were received at each centre, and where and if data were not received. A report is issued each month.

6.5.2 In recent years the JJYY form of BATHY code (the form described in this document) is being used. Each month a report is compiled documenting the progress in switching from the older code form (JJXX form) to the newer one.

6.5.3 On a monthly basis, a data quality report is assembled that shows which platforms have had higher rates of problems in their data collections. Ship's operators are notified so that they can take actions to correct these noted problems.

6.5.4 A display of where profiles were collected is made both on a monthly basis and in the previous 12 months. This is used to monitor the global sampling and where possible adjust the sampling to provide a more uniform coverage of the oceans.