SOLAS Ch V - Regulations
1. Application
2. Definitions
3. Exemptions & Equivalents
4. Navigation Warnings
5. Meteorological Services & Warnings
6. Ice Patrol Services
7. Search & Rescue Services
8. Life-Saving Signals
9. Hydrographic Services
10. Ship's Routeing
11. Ship Reporting Systems
12. Vessel Traffic Services
13. Aids to Navigation
14. Ships' Manning
15. Bridge Design
16. Maintenance of Equipment
17. Electromagnetic Compatibility
18. Navigational Systems & Voyage Data Recorder
19. Shipborne Navigation Systems
20. Voyage Data Recorders
21. International Code of Signals
22. Navigation Bridge Visibility
23. Pilot Transfer Arrangements
24. Use of Heading/Track Control Systems
25. Electrical Power
26. Steering Gear
27. Charts & Nautical Publications
28. Records of Navigational Activities & Daily Reporting
29. Distress Signals
30. Operational Limitations
31. Danger Messages
32. Information Required in Danger Messages:
33. Distress Situations
34. Safe Navigation
34-1 Master's Discretion
35. Misuse of Distress Signals
Regulation Appendix
A1. Categories of Waters & Classes of Ships
A2. Table of Requirements for Ships
A3. Nautical Charts & Publications
A4. WMO Maritime Services
A5. Routeing Systems
A6. Safe Manning
A7. Equipment Manuals
A8. Performance Standards & Type Approval
A9. Performance Standards for Navigational Equipment
A10. Voyage Data Recorders
A11. Navigation Equipment - New Ships
A12. Navigation Equipment - Existing Ships
A13. Magnetic Compass
A14. Electronic Charts
A15. Radar Reflectors
A16. Radar Equipment
A17. Automatic Identification Systems
A18. Steering Gear, Heading & Track Control Systems
A19. High Speed Craft Code
A20. Inspection & Survey of Navigational Equipment
A21. Pilot Transfer Arrangements
A22. Recording of Navigational Events
A23. Passenger Ship Operational Limitations
A24. Voyage Planning
A25. Guidelines for Voyage Planning
Annex 4 - WMO Maritime Services

From  “Application of Meteorology Programme” Chapter 6, WMO, Geneva (Revised unedited version)

The WMO Voluntary Observing Ships’ scheme


6.1   Introduction
6.2   Classification of voluntary observing ships

6.3   Recruitment of voluntary observing ships
6.4   Meteorological observations from ships
6.5   Meteorological instrumentation on board ships

6.6   Transmission of ship’s observations to the shore

6.7   Distribution of ships’ weather reports over the GTS

6.8   Meteorological logbooks for ships

6.9   Port Meteorological Officers

6.10  Incentive programme for voluntary observing ships

6.11  Marine meteorological publications produced by national Services for seafarers and marine observers

6.1) Introduction

The international scheme by which ships plying the various oceans and seas of the world are recruited for taking and transmitting meteorological observations is called the "WMO Voluntary Observing Ships’ Scheme". The forerunner of the scheme dates back as far as 1853, the year in which delegates of 10 maritime countries came together at a conference in Brussels, on the initiative of Matthew F. Maury, then director of the U.S. Navy Hydrographic Office, to discuss the establishment of a uniform system for the collection of meteorological and oceanographic data from the oceans and the use of these data for the benefit of shipping in return. In the twentieth century, the system was recognized in the International Convention for the Safety of Life at Sea, which specifies in Regulation 4 of Chapter V — Safety of navigation - that "the Contracting Governments undertake to encourage the collection of meteorological data by ships at sea and to arrange for their examination, dissemination and exchange in the manner most suitable for the purpose of aiding navigation".

Voluntary observing ships make a highly important contribution to the Global Observing System of the World Weather Watch. Relevant standard and recommended practices and procedures are contained in Part III, Section 2.2.3 of the Manual on the Global Observing System (WMO-No.544). Although new technological means, such as satellites and automated buoys, are used to gather data from the oceans, the voluntary observing ships continue to be the main source of oceanic meteorological information.

From the beginning shipping has assisted in the scientific exploration of the oceans and also in the development of suitable measuring techniques for use by shipborne observers. Nowadays, the cooperation of voluntary observing ships is sought in each of the large-scale scientific experiments conducted by special research vessels to furnish the additional data needed for complete analyses of environmental conditions. In addition, the participation of these ships is regularly requested in technical studies and investigations concerning observing methods, such as the measurement of sea-surface temperature, precipitation, wind, etc.

6.2) Classification of voluntary observing ships

6.2.1) Types of surface synoptic sea stations

Meteorological observing stations include surface synoptic sea stations of different types. The terminology used in the Manual on the Global Observing System, Part III, Section 1 is as follows:

Sea stations:

  • Fixed sea stations
  • Ocean weather stations
  • Lightship stations
  • Fixed platform stations
  • Anchored platform stations
  • Island and coastal stations
  • Mobile sea stations
  • selected ship stations
  • supplementary ship stations
  • auxiliary ship stations
  • ice-floe stations
  • Automatic sea stations*
  • fixed sea stations
  • mobile sea stations
  • drifting buoy stations

* Data may be asynoptic when collected by satellite

Since this Guide emphasises the mutual collaboration between marine users and meteorologists, only the activities of Meteorological Services with regard to mobile ship stations are described in the following paragraphs. There are three types of mobile ship stations engaged in the WMO Voluntary Observing Ships’ Scheme, namely:

a.) Selected ship stations;

b.) Supplementary ship stations;

c.) Auxiliary ship stations.

The types of observation normally made by each of these types of ship stations is shown in Table 6.2 under paragraph below.

6.2.2) Selected ships

A selected ship station is a mobile ship station which is equipped with sufficient certified meteorological instruments for making observations, transmits regular weather reports and enters the observations in meteorological logbooks. A selected ship should have at least a barometer (mercury or aneroid), a thermometer to measure sea-surface temperature (either by the bucket method or by other means), a psychrometer (for air temperature and humidity), a barograph, and possibly, an anemometer.

Selected ships constitute the large majority of voluntary observing ships.

6.2.3) Supplementary ships

A supplementary ship station is a mobile ship station equipped with a limited number of certified meteorological instruments for making observations, transmits regular weather reports and enters the observations in meteorological logbooks.

6.2.4) Auxiliary ships

Beyond the shipping lanes normally used by selected or supplementary ships very few observations are available. Ships in these data-sparse areas, although not equipped with certified instruments, may be asked to make and transmit weather reports. They are classified as ‘auxiliary ships’. An auxiliary ship station is a mobile ship station, normally without certified meteorological instruments, which transmits reports in a reduced code form or in plain language, either as a routine or on request, in certain areas or under certain conditions.

6.2.5) International List of Selected, Supplementary and Auxiliary Ships

Selected, supplementary and auxiliary ships constitute an important source of marine data which are used for various purposes all over the world. In analysing these data, Meteorological Services should be aware of the type of instrumentation on board a given ship, or the particular method of observation when several methods are generally in use. For this purpose WMO has compiled an International List of Selected, Supplementary and Auxiliary Ships which is kept up to date through information supplied by Members, and for each ship, contains particulars such as:

a.) Name of ship;
b.) Call sign;
c.) Vessel type;
d.) Vessel dimensions;
e.) Area or routes over which the ship normally plies;
f.) Type of barometer;
g.) Type of thermometer;
h.) Exposure of thermometer;
i.) Type of hygrometer or psychrometer;
j.) Exposure of hygrometer or psychrometer;
k.) Method of obtaining sea surface temperature;
l.) Type of barograph;
m.) Various other meteorological instruments used aboard the ship;
n.) Types of radio equipment, including INMARSAT;
o.) Height of barometer, in metres, measured from maximum load line;
p.) Height of anemometer, in metres, measured from maximum load line;
q.) Depth of sea temperature measurement.

Regular updating of the International List of Selected, Supplementary and Auxiliary Ships is required (see Manual on the Global Observing System, Part III, paragraphs and because of the frequent changes in the international merchant fleet and also the changes in the recruitment of auxiliary ships in particular. Members are asked to provide to the WMO Secretariat every quarter, updates of their list of selected, supplementary and auxiliary ships, preferably on diskette. A diskette is the most efficient means of keeping the master list updated, as no retyping is required. The Secretariat will make available a copy of the master list every quarter, also on diskette, to interested Members. In addition, the Secretariat distributes a hard copy of the master list annually.

6.3) Recruitment of voluntary observing ships

6.3.1) Requirement to recruit ships

According to the Manual on the Global Observing System, Volume I, Part III, paragraph, each Member shall arrange for the recruitment of ships that are on the national register of that Member as mobile sea stations. In fulfilling this obligation, each Member contributes to the common objective of obtaining sufficient coverage of meteorological observations over the sea. While a uniform coverage of the oceans is desirable, this is difficult to achieve in view of the large differences in the density of shipping traffic. This traffic is comparatively dense in the northern hemisphere, but this is not the case in the tropics or in the southern hemisphere. Consequently, greater attention should be given to the recruitment of voluntary observing ships in these areas. Meteorological Services in many countries are required to provide more detailed information of the weather and sea conditions in coastal areas. Some Services have successfully recruited ships of local companies to make and transmit observations during their voyage from harbour to harbour along the coast. Such ships may be recruited as supplementary or as auxiliary ships. Their observations have everywhere been found to be of great value.

6.3.2) Criteria for recruitment

Several criteria can be used in deciding whether a particular ship should be recruited as a selected, supplementary or auxiliary ship, to satisfy both national and international needs. Questions which should be examined are whether all the necessary instruments can be installed, whether the ship's officers will have the time available for recording and transmitting the observations and whether the necessary regular contact can be established for the receipt of meteorological logbooks. Generally shipowners and masters are very cooperative in these matters; however, it is advisable that these questions be thoroughly discussed at the recruiting stage.

Countries may recruit ships of foreign registry which visit the ports of the recruiting country sufficiently often to permit regular contact. This recruitment is sometimes done by arrangement between the Meteorological Services of two countries concerned. In order to avoid the entry of duplicate data into the international archiving system, meteorological logbooks from ships of foreign registry should be procured and stored through appropriate arrangements with the Meteorological Service of the country of registry. When a ship of foreign registry is recruited, the Member in whose country the ship is registered should be notified, unless a port in the country of the Member which recruits the ship is considered to be its home port.

For the recruitment of an auxiliary ship, no prior arrangements are required with the Meteorological Service of the country of registry.

Members should establish a suitable organisational unit for the recruitment of voluntary observing ships. This unit should contact shipping agencies to enlist their cooperation, arrange for the provision of instruments, instructive material and other necessary documents to ships, arrange for the collection and examination of the ships’ meteorological logbooks, arrange for visits to ships, and to look after the various financial questions involved. Port meteorological officers can play a large role in the recruitment of ships.

Complaints about meteorological observations from a particular observing ship should be directed to the Member with which the ship is registered. If the ship was recruited by another Member, the Member receiving the complaint should forward it to the Member concerned.

6.4) Meteorological observations from ships

6.4.1) Danger messages

The International Convention for the Safety of Life at Sea, 1974, in its Regulation 2, Chapter V, concerning the safety of navigation, specifies that the master of every ship is bound to issue a danger message when a ship meets with objects or conditions which are of direct danger to navigation. As far as meteorological phenomena are concerned, danger messages should contain information on:


Tropical cyclones (tropical storms) and their development;

b.) Winds of force 10 or above on the Beaufort scale for which no storm warning has been received;
c.) Sub-freezing air temperatures associated with gale force winds causing severe ice accretion on super-structures;
d.) Sea ice or ice of land origin (e.g. icebergs).

Details concerning the contents of danger messages and their transmission are described in Regulations 31 and 32  of Chapter V of the International Convention for the Safety of Life at Sea. The information given in these messages directly serves the safety of navigation. Those containing meteorological information are of vital importance to Meteorological Services for the preparation of weather and sea bulletins.

6.4.2) Surface observations Content of surface observations from ships

The elements observed by the various types of voluntary observing ship are shown in Table 6.2.

Table 6.2 - Observations made by mobile ships stations





Present and past weather




Wind direction and speed




Cloud amount




Cloud type and height of base












Humidity (dew point)


a a

Atmospheric pressure




Pressure tendency


a a

Ship’s course and speed


a a

Sea temperature


a a

Direction, period and height of waves


a a

Sea ice and/or icing




Special phenomena


a a

Supplementary and auxiliary ships are sometimes asked to add observations of waves to their reports. Programme for surface observations on board ships

The basic programme for making surface observations on board ships consists of the following procedures:

a.) Synoptic observations should be made at the main standard times: 0000, 0600, 1200 and 1800 UTC. When additional observations are required, they should be made at one or more of the intermediate standard times: 0300, 0900, 1500 and 2100 UTC;

b.) While taking observations, atmospheric pressure should be read at the exact standard time, the observation of other elements being made within the ten minutes preceding the standard time;

c.) When operational difficulties on board ship make it impracticable to make the synoptic observation at a main standard time, the actual time of observation should be as near as possible to the main standard times. In special cases, the observations may even be taken one full hour earlier than the main standard time i.e. at 2300, 0500, 1100 and 1700 UTC. In these cases the actual time of observation should be indicated; however, these departures should be regarded only as exceptions;

d.) When sudden or dangerous weather developments are encountered, observations should be made for immediate transmission without regard to the standard times of observation (see paragraph 6.4.1 above for obligations under the International Convention for the Safety of Life at Sea);

e.) Observations should be made more frequently than at the main standard times whenever storm conditions threaten or prevail. Meteorological Services may request more frequent observations for storm warnings, particularly for tropical cyclones. Special observations may also be requested for search and rescue or other safety reasons;

f.) Supplementary observations when required for scientific studies should be made at intermediate standard times, subject to non-interference with navigation duties;

g.) When an observation is made at 0300, 0900, 1500 or 2100 UTC in order to ensure its transmission to a coastal radio station, it is desirable that the observation at the next main standard time should be made for climatological purposes, and if possible transmitted in accordance with normal procedures;

h.) Ships’ officers should be encouraged to continue taking and reporting observations while the ships are in coastal waters, provided it does not interfere with their duties for the safety of navigation;

i.) Transmission of ships’ observations by INMARSAT is not constrained by the watchkeeping hours of radio officers aboard ship; transmission can be made at any time. Observation of sea and swell

The distinction between two separate wave trains, and, in particular, the distinction between sea and swell, can be difficult for an inexperienced observer. Sea waves are systems of waves observed at a point which lies within the wind field producing the waves. Swell waves are systems of waves observed at a point remote from the wind field which produced the waves, or observed when the wind field which generated the waves no longer exists.

The distinction between sea and swell can be made on the basis of one of the following criteria:

Wave direction — if the mean direction of all waves of more or less similar characteristics differs 300 or more from the mean direction of waves of different appearance, then the two sets of waves should be considered to belong to separate wave systems.

Appearance and period — when typical swell waves, characterised by their regular appearance and long-crestedness, arrive approximately, i.e. within 20°, from the direction of the wind, they should be considered as a separate wave system if their period is at least four seconds greater than the period of the larger waves of the existing sea.

More guidance on the observation of waves and swell, as well as the observation of sea ice, can be found in the Guide to Meteorological Instruments and Methods of Observation (WMO-No. 8) Part II, Chapter 4, Marine observations.

6.4.3) Upper air observations

In the past very few mobile ship stations were equipped for making upper-air synoptic observations. An automated means of making upper air soundings from a merchant ship has now been developed under the Automated Shipboard Aerological Programme (ASAP). The balloon can be automatically filled and released, and observations received and encoded under the supervision of a ship’s officer. Nevertheless, the number of ships making upper-air observations is still small.

An upper-air synoptic observation consists of one or more of the following elements:

a.) Atmospheric pressure;

b.) Air temperature;

c.) Humidity;

d.) Wind speed and direction.

The standard times of upper-air synoptic observations are 0000, 0600, 1200 and 1800 UTC. The actual time of regular upper-air synoptic observations should be as close as possible to 30 minutes before these standard times, and should not fall outside the 45 minutes prior to the standard time. The actual time of a pilot-balloon observation may deviate from this time range if by doing so observed winds to considerably greater heights can be obtained.

In the basic programme of upper-air soundings from mobile ships the general objective is to obtain reports from positions which are not more than 1000 km apart and the observations are normally required at 0000 and 1200 UTC. These observations are to be coordinated within the framework of an international programme to ensure that data are obtained from those parts of the oceans where upper-air data are needed. On the other hand, as these observations are scheduled according to circumstances, Members establishing a programme of upper-air observation on board voluntary observing ships should communicate to the Secretariat the following information:

a.) Name and call sign of the ship;

b.) The routes on which the ship normally plies and the zones in which the upper-air observations will be taken;

c.) The means of communication of the reports, and if coastal radio stations are to be used, the names of these stations;

d.) The scheduled dates of departure and arrival at various ports;

e.) Details of the observing programme scheduled for the voyage;

On receipt, these particulars will be notified by the Secretariat to other Members.

6.4.4) Sub-surface observations

Selected ships may also be equipped for the taking of bathythermograph observations during ocean crossings. The use of an expendable bathythermograph (XBT) does not oblige the ship to reduce speed or make course alterations. All arrangements for this type of observation are made within the framework of the Integrated Global Ocean Services System (IGOSS) jointly operated by WMO and IOC.

Procedures for the collection and exchange of BATHY and TESAC (temperature, salinity and current) observations are specified in the Guide to Operational Procedures for the Collection and Exchange of IGOSS Data (IOC/WMO Manuals and Guides No. 3) and the WMO Manual on the Global Telecommunications System, Volume 1, Part 1, Attachment I-1 (WMO-No. 386).) The preferred times for BATHY and TESAC observations are 0000, 0600, 1200 and 1800 UTC. However observations taken at any time are useful and should be transmitted.

6.4.5) Special observations

In relation to international programmes of scientific or economic significance, observations of a special nature are needed from ships at sea and WMO is requested to assist through its Voluntary Observing Ships’ Scheme. One such example is the request for observations on locust swarms in the seas around Africa, Arabia, Pakistan and India. This programme is of great importance to the agricultural economy in the countries concerned.

Another example is the logbook report of freak waves. A freak wave is defined as a wave of very considerable height ahead of which there is a deep trough. It is the unusual steepness of the wave which makes it dangerous to shipping. Favourable conditions for the development of freak waves seem to be strong current flows in the opposite direction to a heavy sea and especially when this occurs near the edge of the continental shelf. The reports may contribute to a mapping of these particularly dangerous areas and to a better understanding of the phenomenon.

Sea-surface currents are a further special observation. These data are derived from measurement of ships’ set and drift and form the basis for consideration of the ocean surface current circulation. They are of value to research and climatic studies and are collated by the International Surface Current Data Centre in the United Kingdom which sends a copy of the stored data to the World Data Centres for Oceanography. All vessels are encouraged to obtain such data, on a voluntary basis, to improve the data base.

6.4.6) Coding of observation

Ships’ observations are coded in the international meteorological codes published in the Manual on Codes, Volume I (WMO -No. 306). The various code forms are given code names which are sometimes included in the heading of the ship's report. In all cases, however, a 4-letter identification group is used (see code 2582 in the Manual on Codes). The identification groups used by ships are shown in Table 6.3.

Table 6.3

Identification groups of codes reported by SHIPS

Code name

Identification group(s)

Content of the code



Surface report from a sea station



Upper-wind report from a sea station; Parts A, B, C, D respectively



Upper-level pressure, temperature, humidity and wind report from a sea station; Parts A, B, C, D respectively



Bathythermal observation



Observation of temperature, salinity and current from a sea station



Report of a marine surface observation along a ship’s track

6.4.7) Automation of observations on board ship

Automation of shipboard observations has been advanced by the advent of personal computers and satellite communications. In one form the observations are taken manually in the traditional way and then entered into a personal computer, which may be in the form of a laptop or notebook. The computer programme then:

a.) Provides screen prompts to assist with data entry;

b.) Calculates the true wind, MSL pressure and dew point;

c.) Checks validity of some data, e.g. month in range 1–12, observations near climatological extremes;

d.) Stores the observation in SHIP code on disc and prints it out for transmission;

e.) Formats the observation in IMMT format (refer Chapter 3, paragraph 3.2.7) and stores it on disc or transmits the data to a shore station via a satellite system.

If the ship is equipped with INMARSAT-C, the computer diskette can be placed in the INMARSAT terminal and transmitted without re-keying. In addition to filling in a meteorological logbook the diskette of observations in IMMT format is sent periodically to the Meteorological Office.

Another form of automation is the Marine Data Collection Platform (MDCP), which consists of a hand-held computer, air temperature and air pressure sensor, transmitter and antenna. The coded SHIP observations are entered into the computer and collected by Service Argos satellite. In this case the meteorological logbook still has to be entered manually and returned to the Meteorological Office in the traditional way.

Completely automated shipboard weather stations present difficulties. Proper locations for sensors are not easy to find, particularly for wind and dew point, while equipment for automated measurement of visibility, weather, clouds and wave height cannot be accommodated in the confined space of a ship.

6.5) Meteorological instrumentation on board ships

6.5.1) General

Full guidance upon the basic meteorological instruments suitable for use on board ships making observations under the Voluntary Observing Ships Scheme, together with advice on methods of observations, is provided in the Guide to Meteorological Instruments and Methods of Observation (WMO-No. 8) Part II, Chapter 4, Marine observations.

Experience over several years has indicated that certain features of the present instrumentation fitted to ships require constant attention. The following comments emphasize those aspects to which special care should be given and are fully complementary to the general guidance in the above-mentioned Guide.

6.5.2) Instruments measuring atmospheric pressure

In practice the proper installation and operation of mercury barometers at sea has proved very difficult, and mercury barometers are now rarely installed on board ships. The use of precision aneroid barometers on the other hand does not give rise to similar problems. However, because of the zero drift to which these instruments are liable, frequent checking against standing barometers is necessary in order to ensure proper continuous operation. The zero drift of aneroids currently in use is seldom continuous, the instrument correction remaining stable for a rather long period of time, then suddenly dropping to another level. Checking procedures should therefore continue routinely even if the correction has remained stable for some time. This checking should be carried out by a PMO whenever possible, preferably at intervals not exceeding three months. A permanent record of all such checks should be attached to the instrument and should include information on the date of the check and the temperature and pressure at which the check was made.

On board small vessels the reduction of the pressure reading to MSL may be carried out by the addition of a given reduction constant, or simply by correcting the reading of the scale to give pressure at MSL directly. When the elevation of the barometer varies significantly with the loading of the ship, the use of different reduction constants has to be considered. The draught of very large tankers can vary between a sea-going ballast condition and a fully-loaded condition by as much as 10 metres. If the barometer elevation is great, air temperature may also have to be taken into consideration when preparing reduction tables. At all times the limit of accuracy of the applied reduction should be kept within 0.2 hPa.

Barographs used on board ships should be supplied with an efficient built-in damping device and the instrument should be mounted on shock-absorbing material in a position where it is least likely to be affected by concussion, vibration or movement of the ship. The best results are generally obtained from a position as close as possible to the centre of flotation. The barograph should be installed with the pen arm oriented athwart-ship to minimize the risk of its swinging off the chart

6.5.3) Instruments measuring wind speed and direction

In order that wind reports from ships equipped with instruments are comparable with estimated winds and wind reports from land stations, anemometer readings should be averaged over 10 minutes. It is difficult to estimate 10-minute means by watching the dial of an anemometer. An overestimation of more than 10% is not uncommon. It is therefore preferable that the instrument readout used for reporting wind velocities be automatically averaged over 10 minutes. If such readouts are not available, careful instructions should be given in order to avoid overestimation.

Due to the flow distortion caused by superstructure, masts and spars, the site of the anemometer sensor has to be carefully selected, preferably as far forward and as high as possible. The wind speed needs to be corrected for effective height (See Marine Meteorology and Related Oceanographic Activities Report No. 22 Reduction of wind measurements at sea to a standard level by R. J. Shearman and A. A. Zelenko (WMO/TD-No. 311)).

Any anemometer mounted on a ship measures the movement of air relative to the ship, and it is essential that the true wind be computed from the relative wind and the ship’s velocity. A simple vector diagram may be used, although in practice this can be a frequent source of error. Special slide rules and hand computers are available and programs can be installed on small digital computers.

6.5.4) Instruments measuring temperature and humidity

Temperature and humidity observations should be made by means of a psychrometer with good ventilation, exposed in the fresh airstream on the windward side of the bridge. The use of a louvred screen is not as satisfactory. If it is used, two should be provided, one secured on each side of the vessel, so that the observation can be made on the windward side. The muslin and wick fitted to a wet-bulb thermometer in a louvred screen should be changed at least once a week, and more often in stormy weather.

Automated or distant-reading thermometers and hygrometers should be sited in a well-ventilated screen with good radiation protection and placed as far away from any artificial source of heat as practicable. It is advisable to compare the readings with standard psychrometer observations at the windward side of the bridge at regular intervals, particularly when new types of equipment are introduced.

6.5.5) Instruments measuring sea temperature

It is important that the temperature of the uppermost thin film of water (measured by infra-red radiometers) should be distinguished from the temperature of the underlying mixed layer. It is the representative temperature of the mixed layer which should be reported by voluntary observing ships. The "bucket" instrument method is the simplest and probably the most effective method of sampling this mixed layer, but unfortunately the method can only be used on board small vessels moving slowly. Other methods are:

a.) Intake and tank thermometers, preferably with distant reading display and used only when the ship is moving;

b.) Hull-attached thermometers located forward of all discharges;

c.) Trailing thermometers; and

d.) Infra-red radiometers.

These instruments are described in Part II, Chapter 4 of the Guide to Meteorological Instrument and Observing Practices (WMO-No.8).

6.6) Transmission of ship’s observations to the shore


Ship reports can be transmitted readily to a Coast Earth Station (CES) which has been authorised to accept these reports at no cost to the ship. The national Meteorological Service of the country operating the CES pays the cost, which is usually less than the cost of a report received via coastal radio. There are a number of such CESs in each satellite footprint and they are listed, together with the area from which they will accept reports, in WMO-No. 9, volume D, Part B. Code 41 is the INMARSAT address which automatically routes the report to the Meteorological Service concerned. To place a limit on the costs incurred by a national Meteorological Service, a CES may be authorised to accept reports only from ships within a designated area of ocean. These limits should be drawn to the attention of the relevant ship’s officers when recruiting a ship under the Voluntary Observing Ships Scheme. A radio operator is not needed to transmit the report, and hence transmission is not restricted to the operator’s hours of duty.

6.6.2) Coast Radio Stations

Ship reports can be transmitted by radio telegraphy to a coastal radio station which has been authorised to accept these reports at no cost to the ship. (The costs are met by the country operating the coastal radio station, in many cases by the national Meteorological Service).

The global plan for the collection of ship reports, and the procedures for the transmission of weather reports to coastal radio stations are described in the Manual on the Global Telecommunications System, Volume 1, Part 1, Section 2.6 and Attachment I-1 (WMO-No 386).

Weather reports from mobile ship stations should (without special request) be transmitted from the ship to the nearest coastal radio station situated in the zone in which the ship is navigating. If it is difficult, due to radio propagation conditions or other circumstances, to contact promptly the nearest radio station in the zone in which the ship is navigating, the weather messages should be cleared by applying the following procedures in the order given below:

a.) Transmission to any other coastal radio station in the zone in which the ship is navigating;

b.) Transmission to any coastal radio station in an adjacent zone within the same Region;

c.) Transmission to any coastal radio station in any other zone within the same Region;

d.) Transmission to a coastal radio station in an adjacent zone in a neighbouring Region, or, failing that, to any other station in neighbouring Region;

e.) Transmission to another ship or an ocean weather station with the function or willing to act as a relay station.

In zones situated along the borderline between two Regions, the order of the procedures for the transmission of ships' weather reports to coastal radio stations, as laid down in sub-paragraphs (a), (b), (c), (d) and (e) above, may be interchanged subject to agreement between the two Regional Associations involved. Any agreement reached on this matter should specify the limits of the area concerned.

Members may issue instructions to their mobile ship stations to the effect that their weather reports may be transmitted via one of their home coastal radio stations designated for the collection of reports from the zone, if the application of such procedures may facilitate the efficient contact with coastal radio stations and the clearing of weather messages.

On most voluntary observing ships there is only one radio officer, whose watch-keeping hours total eight per day, hence he/she is not always available at the time when a weather report is ready for transmission. Watch-keeping hours are based on local standard time where the ship happens to be, and these times do not always synchronize with coordinated Universal Time (UTC) used for meteorological observations. It is desirable that watchkeeping hours are chosen so that as many ships’ observations at the main standard times (0000, 0600, 1200, 1800 UTC) as possible can be transmitted immediately after the observations are taken.

Observations taken while the radio officer is off duty should be sent at the first opportunity even with a delay of up to 12 hours. In the southern hemisphere and other areas where few ships’ weather reports are available they should be sent up to 24 hours after the time of observation.

In transmitting meteorological reports to coastal radio stations, ships' radio officers follow the regulations which are valid for Maritime Mobile Services, as defined in the ITU Radio Regulations.

Coastal radio stations designated to receive ships' weather reports should, for the purpose of receiving the reports:

a.) Keep a continuous 24-hour watch; or

b.) Keep a watch for at least 30 minutes beginning at 0000, 0600, 1200 and 1800 UTC daily; watch should also be kept for a similar minimum time at the beginning of the nearest "single-operator period" following those standard synoptic hours;

c.) Keep watch for shorter periods (stations with limited hours of operation) than those mentioned under (b) above when these stations are considered of particular value.

The list of coastal radio stations accepting ships' weather reports, free of charge to the ship, together with their radio addresses and other relevant particulars, is contained in WMO-No. 9, Volume D, Part B. Members responsible for the reception of meteorological reports from ships need to advise the Secretariat of changes to their coastal radio stations so that this publication can be kept up to date.

The ship weather report must be addressed to the telegraphic address of the relevant National Meteorological Centre. The addresses are included in the information published in WMO-No. 9, Volume D, Part B. The address should be preceded by the abbreviation "OBS" to ensure appropriate handling of the message at the coastal radio station. The coastal radio station must forward the report to the National Meteorological Centre with minimum delay (by telex, landline or other means of electronic communication).

Members whose ships repeatedly encounter difficulties in clearing ships' weather reports with coastal radio stations should communicate promptly with the Member(s) concerned giving full particulars as to dates and times; the presidents of the Commission for Basic Systems and the Commission for Marine Meteorology and the Secretary-General of WMO should also be informed.

6.6.3) Service Argos

Service Argos is a system for receipt of data from automatic weather stations by orbiting satellites. It has been used for many years to collect data from drifting buoys, but is also used to collect data from Marine Data Collection Platforms (MDCPs) on board ships. The data are read out from the satellite at one of three ground stations, and are then distributed on the GTS.

6.7) Distribution of ships’ weather reports over the GTS

Ship weather reports received at a National Meteorological Centre from INMARSAT Coast Earth Stations and coastal radio stations should be assembled into meteorological bulletins and transmitted over the GTS. This should be done with minimum delay, and some Centres transmit a bulletin of available ship weather reports every 15 minutes. The speed of transmission over the GTS has become more important with the advent of INMARSAT, as ship reports which were received at a local coastal radio station and arrived quickly may now be received by a CES in a distant country and have to arrive over the GTS. The ship weather reports are also a vital input to global models run at a number of centres, and there should be minimum delay in receipt of data from all over the world.

6.8) Meteorological logbooks for ships

6.8.1) Layout

The recording of observations in permanent form is obligatory for selected and supplementary ships and recommended for auxiliary ships. On ships where the observations are entered on a personal computer a diskette will be likely to serve as the means of record. Otherwise the observations are recorded in a meteorological logbook. The layout of logbooks is a national responsibility. Generally, the order of parameters recorded in the logbook follows the order of elements in the SHIP code form. Thus the logbook can be used both for recording the synoptic weather report which is to be transmitted and to include in the same format additional information required for climatological purposes. For the latter use, the entries are subsequently transferred on to IMMT format.

Logbooks should contain clear instructions for entering observations. Code books should also be provided, along with logbooks, for ready reference and to correct wrong entries as necessary. It is useful to mark in the logbook those columns which are earmarked for entries to be transmitted as part of the weather report. In some national logbooks, these columns are lightly shaded or coloured and in others they are inserted in a special frame. Also, space is often provided in logbooks to enter the various readings used to compute a meteorological element such as air pressure reduced to sea-level, or actual wind derived from a measured apparent wind and the ship's movement. This will enable a check of the computations carried out on board ship for subsequent quality control of the data during processing for climatological purposes.

The size of a meteorological logbook is usually such as to permit the entries for four days on one sheet, that is, 16 observations made at the four main standard times. Ships should be requested to return a completed logbook to the Meteorological Service or PMO which has recruited the ship. The period covered by a logbook should not be more than three months, so that the delay in entering the observations in the climatological system is not too great.

Logbooks should be returned with information regarding the ship, the instruments used and other details of a general nature, and space should be provided for these entries. The name of the master, the observers and the radio officer should also be included, particularly if an incentive programme exists in the country where the ship has been recruited.

6.8.2) Supply and return

To facilitate the supply of meteorological logbooks to ships which do not regularly visit their home ports, port meteorological officers in various ports keep a stock of logbooks of different National Services. In addition, port meteorological officers may also keep stocks of observing and coding instructions in languages of other countries for supply to ships which may require them. As the method of recording observations on diskette becomes widespread, it may also be necessary for port meteorological officers to keep a stock of these for supply to ships.

Completed logbooks are generally considered the property of the national Meteorological Service which has recruited the ship. As they contain the results of work done on a voluntary basis, they should be kept for a sufficent number of years to permit examination of the original entries. Such an examination is often required to satisfy requests from the ships’s officers concerned or from the shipping company. Sometimes, special arrangements are made between countries whereby one country takes care of all recruitment procedures, but the completed logbooks are sent to the country of registration. In such cases, the country which has recruited the ship receives a copy of the completed logbook when so desired.

6.8.3) Scrutiny of entries

There is always a possibility of errors occurring in the entries in a logbook however clear the instructions might be and despite the care taken by the observer in his work. Completed logbooks must therefore be scrutinised upon receipt and obvious errors corrected. It is of great importance that the types of errors which are made frequently be brought to the attention of the observers concerned so that any misinterpretation of the instructions or erroneous practices in reading instruments or making entries can be corrected. When the logbooks are received by the port meteorological officer, or section of the national Meteorological Service dealing with voluntary observing ships, a first check should be made as soon as possible to permit a personal conversation with the appropriate ship’s officers. Such conversations or written responses commenting on logbooks which have been received constitute an important element of the continuous training of shipborne observers. Without this feedback information the officers would soon become uncertain as to the quality of their work or the implementation of certain observing or coding procedures and, with an inevitable waning of interest, the quality of their observations may deteriorate.

Similar scrutiny and personal liaison is especially important in respect of special observations of freak waves, sea-surface currents, etc. Without the willing cooperation of marine observers, these non-routine data would not be available.

Ships’ officers often include questions on coding matters or on any special phenomena observed by them in the "remarks" column of the logbook. Response to these questions is important, as this falls within the same spirit of maintaining interest in meteorological work. Some countries have instituted special periodicals for meteorological observers on board their ships in which these questions are discussed and explained (see paragraph 6.11 below).

6.9) Port Meteorological Officers

In recruiting voluntary observing ships and assisting them in their meteorological work, direct contact with ships’ officers is often needed to provide them with instructive material and other documents, to inspect meteorological instruments on board ships, to collect completed logbooks of observations and, on an initial check, take such corrective action as is possible by personal contact. For this purpose, port meteorological officers having maritime experience should be appointed at main ports.

Port meteorological officers are representatives of the Meteorological Service of the country as far as the local contact with maritime authorities is concerned. The role of port meteorological officers is a very important one and the efficiency of the voluntary system of ships' observations often depends on the initiative displayed by these officers. They are in a good position to discuss with ships’ officers any problems they have encountered and offer suggestions, bring to their attention any changes in procedures that may have taken place and give them the latest information which they may desire. Opportunity should also be taken to explain various meteorological and/or oceanographic programmes whenever observations are specially needed from ships. Meteorological instruments on board ships should be checked and other advice or assistance in meteorological matters should be given by port meteorological officers upon request by the master of any ship, irrespective of the its State of registry.

The port meteorological officers should also report to the meteorological authorities in their country if the meteorological work done on board the ship has not been entirely satisfactory. Members should immediately react to these reports; when they concern the work carried out under the authority of another Member, the latter should be informed. If action has to be taken upon complaints this can best be done through the port meteorological officers who can play a very important role by a tactful approach to the masters and, if constructive criticism is expressed in positive terms, goodwill can be maintained all round.

The scope of the work of port meteorological officers depends largely on the importance of the marine traffic in the particular area served. Before deciding to establish a port meteorological officer in a given port, a study must be made of the various services which should be provided. As marine activities develop, a review should be made from time to time to see whether new services should be provided. Guidelines for organising port meteorological officer activites are given in Annex 6.G to this Chapter. Useful information on the role of port meteorological officers can be found in Marine Meteorology and Related Oceanographic Activities Report No. 30, Proceedings of the International Seminar for Port Meteorological Officers (1993) (WMO/TD-No. 584).

A list of port meteorological officers with their addresses and telephone numbers is contained in WMO-No. 9, Volume D, Part C; the list should be provided nationally to ships’ officers to facilitate their contact with port meteorological officers.

6.10) Incentive programme for voluntary observing ships

In recognition of the valuable work done by ships’ officers in taking and transmitting meteorological observations and as an incentive to maintain the high standard of the observations many maritime countries have established a national award or certificate system. These systems vary greatly from country to country; in some countries the ships receive the awards, while in other countries awards are made to the masters or navigation and radio officers individually. Sometimes recognition for the meteorological work done on board ships is given in the form of books, charts and other documents presented to the ship.

Members are encouraged to continue the practice of issuing national awards or certificates to selected, supplementary and auxiliary ships recruited by them, or to the ships’ personnel, as a sign of their participation in the WMO Voluntary Observing Ships’ Scheme.

6.11) Marine meteorological publications produced by national Services for seafarers and marine observers

A number of national Meteorological Services in maritime countries publish magazines directed to the masters and officers of ships which cooperate in the WMO Voluntary Observing Ships’ Scheme. Although content and format differ widely, all these periodicals have two goals in common: first to stress the importance of ships' participation in the marine observing programme and second to offer timely marine meteorological information of interest.

Among the material included in these periodicals are:

a.) Incidents where ships’ observations proved particularly useful;

b.) Commendations on active participation in the WMO Voluntary Observing Ships’ Scheme;

c.) Hints on observing practices;

d.) Changes in broadcast schedules of weather and sea bulletins or radio-facsimile broadcasts;

e.) Articles on important weather features of particular ocean areas.

Members are encouraged to produce such periodicals and to provide them to voluntary marine observers.


© Crown Copyright.