Marine Frequently Asked Questions
Marine Frequently Asked Questions
- How to access marine data?
- What are the obligations for national institution for marine meteorological services?
- What is the Douglas scale and is it appropriate terminology ?
- What is the Beaufort scale ? What is Sea State ?
- What is the GMDSS ?
- What is Code 41 (or Inmarsat Code-41) ?
- What is WMO Publication No. 47 (Pub 47) ?
- What is swell ?
- What is a storm surge ?
- What are the recommended observing practices ?
- How do I get buoy WMO identification numbers ?
- How to participate in the Voluntary Observing Ship (VOS) scheme ?
- How to make Voluntary Observing Ship (VOS) data available to the WMO ?
- How to share buoy data ?
1. How to access marine data?
On the "Access to Data and Services" of JCOMM.info, you will find links to various sources for marine meteorological and oceanographic data.
Historical Data can be requested from the International Comprehensive Ocean-Atmosphere Data Set (ICOADS). More details on ICOADS and how to access the data on its web site are available at: http://icoads.noaa.gov/products.html .
Real-time data are normally being exchanged internationally via the Global Telecommunication System (GTS) of the World Weather Watch (WWW). GTS data are exchanged according to WMO Resolution 40 (Cg. XII). Annex 1 to the Resolution defines “Essential” Data and Products to support WMO Programmes and which Members shall exchange without charge and with no conditions on use. All available in situ observations from the marine environment as well as upper air observations (e.g. ASAP soundings) are regarded as “Essential” by the Resolution (see the text of the Resolution here). These can be requested by contacting any Permanent Representative of a National Meteorological and Hydrological Service (NMHS) with WMO (see WMO Publication No. 5 for their references). GTS data will gradually be integrated in the WMO Information System (WIS) which will also eventually provide for Data Discovery, Access and Retrieval service (DAR).
In addition, it is possible to access real-time data through international programmes such as ODP (Ocean Data Portal), GODAE (Global Data Assimilation Experiment), CLIVAR (Variability and predictability of the ocean-atmosphere system). They provide data posted by experts and accessible to a large number.
Data Centres: In situ observational data are also provided by specific data centres depending upon the type of observing platform. JCOMM (here) and JCOMMOPS (here) both provide complementary lists of such centres .
2. What are the obligations of the national institutions for marine meteorological services?
Obligations of National Meteorological Services in the implementation of Marine Meteorological Services (MMSs) are detailed in the Manual on Marine Meteorological Services (WMO-No.558). It provides detailed information on
- international obligations of national meteorological agencies to provide MMS for the high seas
- international obligations of national meteorological agencies to provide MMS for coastal and off-shore areas
- international obligations regarding services for main ports and harbour areas
3. What is the Douglas scale and is it appropriate terminology?
References to Douglas Scale appear more regularly in the maritime literature. The following terminology is recommended for use, such as supplying weather information and forecasts for shipping, publications, pilots, etc.:
For the length of swell waves:
Short 0 - 100 m
Average 100 - 200 m
Long over 200 m
For the height of swell waves:
Low 0 - 2 m
Moderate 2 - 4 m
Heavy over 4 m
For the height of sea waves:
Calm (glassy) 0
Calm (rippled) 0 - 0.1 m
Smooth (wavelets) 0.1 - 0.5 m
Slight 0.5 - 1.25 m
Moderate 1.25 - 2.5 m
Rough 2.5 - 4 m
Very rough 4 - 6 m
High 6 - 9 m
Very high 9 - 14 m
Phenomenal over 14 m
In all cases, the exact bounding length or height is included in the lower category, i.e. a sea of four meters is described as rough. When the state of the sea surface is so confused that none of the above descriptive terms can be considered appropriate, the term “confused” should be used. The above-mentioned information is described in detail in the WMO publication No. 8 (Guide to Meteorological Instruments and Methods of Observation) - part II, Chapter 4 (Marine Observations).
4. What is the Beaufort scale? What is Sea State?
The sea state basically specifies wave height. Wave height depends on local winds but on remote winds also (swell).
The Beaufort scale specifies wind speed.
As far as weather observation is concerned, while sea state reporting remains a legal international practice, with modern in situ observing techniques we try to avoid using sea state or Beaufort scale as we prefer direct readings from appropriate instruments (e.g. wave buoys and anemometers respectively). Details about sea state and Beaufort can be found in the WMO Manual on Codes, No. 306, part A, Alphanumeric codes (look for the WMO Code table 3700 (i.e. Sea State) and in Section E for the Beaufort scale).
As far as forecasts and warnings are concerned, WMO does not recommend the use of sea state as it recommends using wave height; however, national meteorological services may be using sea state (e.g. Douglas scale) in some cases instead of wave height but this is not a formal international practice.
5. What is the GMDSS?
The GMDSS is the Global Maritime Distress and Safety System. It is an integrated communications system using satellite and terrestrial radiocommunications to ensure that no matter where a ship is in distress, aid can be dispatched. This System ensures also the provision of Maritime Safety Information (MSI), both meteorological and navigational information, on a global basis at sea. More information is being provided on the JCOMM GMDSS.
6 What is Code 41 (or Inmarsat Code-41)?
In the framework of the GMDSS, meteorological observations from ships – regarded as Maritime Safety Information – can be sent free of charge for the ships if sent via the Inmarsat satellite data telecommunication system using transmission code 41. The cost of transmission is paid by the meteorological service of the receiving country. The list of Inmarsat Land Earth Stations accepting Code 41 is available here.
7. What is WMO Publication No. 47 (Pub 47)?
This is the international list of selected, supplementary and auxiliary ships which contains information about the ships participating in the WMO Voluntary Observing Ships Scheme. Each participating country is providing the WMO Secretariat on a quarterly basis with the list of ships they operate nationally. The catalogue contains a comprehensive range of ship metadata (e.g. ship’s characteristics, meteorological instrument siting) useful for quality monitoring, climate studies, and operational applications. The Publication is available online here.
8. What is swell?
A Swell is any system of water waves that has left its generating area (source: International Meteorological Vocabulary, WMO-No. 182). It is a series of surface gravity waves that are not generated by the local wind. Swell waves often have a long wavelength and a narrower range of frequencies and directions. Information on practical applications for swell and wave forecasting can be found in the Guide to Wave Analysis and Forecasting (WMO-No.702).
9. What is a storm surge?
A storm surge is a difference between the actual water level under influence of a meteorological disturbance (storm tide) and the level which would have been attained in the absence of the meteorological disturbance (i.e. astronomical tide). (source: International Meteorological Vocabulary, WMO - No. 182). Storm surges are caused primarily by high winds pushing on the water surface. Further information can be found in the Guide to Storm Surge Forecasting (WMO-No. 1076).
10. What are the recommended observing practices?
Recommended basic observing practices are detailed in the WMO Guide to meteorological instruments and methods of observation (WMO Publication No. 8). Part II, Observing Systems, Chapter 4, Marine Observations, provides for information and recommendations regarding marine observations from ships, moored buoys, unstaffed light vessels, towers and platforms, as well as drifting buoys.
11. What are the recommended observing practices?
WMO identification numbers are allocated to ocean platforms reporting on the Global Telecommunication System (GTS). WMO numbers are allocated by country depending upon deployment area, and platform type (i.e. drifting buoys, moored buoys, ocean reference sites, and profiling floats). One should normally contact the National Focal Point (NFP) for buoy programmes (here) to obtain WMO numbers. If there is no NFP in your country, you may contact the Ocean Affairs Division of WMO directly (here). More details are provided on the following web page: here
12 How to participate in the Voluntary Observing Ship (VOS) scheme?
WMO welcomes the participation of shipping companies in the Voluntary Observing Ship (VOS) scheme. Ships plying the various oceans and seas of the world are recruited by WMO through the VOS scheme for taking and transmitting meteorological observations. VOS ships make a highly important contribution to the Global Observing System (GOS) of the World Weather Watch (WWW), and increasingly to global climate studies. Detailed information about the Voluntary Observing Ship (VOS) scheme can be found on the following website: http://www.bom.gov.au/jcomm/vos/
The easiest way for interested maritime companies or ship masters to participate in the VOS scheme is to contact the Port Meteorological Officer (PMO) of a port and country where the ship(s) is/are calling regularly, and to discuss the details with him/her. The List of PMOs can be found at: http://www.jcomm.info/pmos
See also the FAQ below regarding how to make VOS data available to the WMO.
13. How to make Voluntary Observing Ship (VOS) data available to the WMO?
Data should be distributed onto the Global Telecommunication System (GTS) using the so-called FM-13 SHIP format. As of 2012, the Binary Universal Form for the Representation of Meteorological Data (BUFR FM-94) should be used instead. These formats are described in the WMO Manual on Codes, WMO No. 306, Volume I, see at:
In the framework of the Global Maritime Distress and Safety System (GMDSS), meteorological observations from ships can be sent free of charge onto the GTS from the ships if sent via the Inmarsat satellite data telecommunication system using transmission code 41. The cost of transmission is paid by the meteorological service of the receiving country. The list of Inmarsat Land Earth Stations accepting Code 41 is available here. However, in recent years, concerns have been expressed by some Meteorological Services supporting most of the related transmission costs because of the increasing concentration of Inmarsat services.
One easy solution for encoding the data according to WMO rules is to use “freeware” Electronic Logbook (e-logbook) software. E-logbook software enables the observer to manually enter the observation into the system which then automatically encodes the data in FM-13 SHIP format The encoded data can then be transmitted through the ship's Inmarsat system using Special Access Code No. 41, with the resultant telecommunication costs paid by the Met Service receiving the data from the Land Earth Station. To date, the following e-logbook software types are available:
- TurboWin (the Netherlands). See http://www.knmi.nl/turbowin/
- ObsJMA (Japan). See http://marine.kishou.go.jp/en/obsjma-en.html
- SEAS (USA). See http://www.aoml.noaa.gov/phod/goos/seas/amverseas_software.php
Other techniques or commercial satellite telecommunication systems can be used such as:
- E-mail transmission via Inmarsat or other means. In practice, ships and/or shipping companies may accept to report meteorological observations through emails at their own expenses. The format is presently FM-13 but it could be easily replaced by compressed or half compressed data files as discussed below.
- Half compression technique through Inmarsat. Data are compressed and formatted in binary, and bits inserted as appropriate in order to obtain a message in alphanumeric form which is suitable for data transmission through Inmarsat. Data are sent ashore to a LES belonging to an Inmarsat provider having a contract with the NMS who recruited the ship; and new Short Access Codes are created for that purpose. Some e-logbooks as described above permit to use this technique. Upon reception at the data processing centre, the extra bits are removed to retrieve the full compressed data message which is processed for GTS distribution purposes. Compared to the normal SAC41 transmission of un-compressed messages, this technique permits significant savings, costs are borne by the meteorological service recruiting the ship (so it is more fair), and does not require the use of FM-13 format which will soon become obsolete.
- Iridium satellite data telecommunication system. Data are compressed and formatted in ASCII or binary format.
In all the above cases, the data are transmitted to shore using some binary or ASCII format defined by the Meteorological Service recruiting the ship. There may be costs to the NMS recruiting the ship associated with these other communications systems. Arrangements must be made with the responsible national meteorological service for the data to be appropriately decoded, converted to geo-physical units, quality controlled, and distributed onto the GTS.
Port Meteorological Officers (PMO) of a port and country where a given ship is calling regularly can be contacted to discuss details and obtain technical assistance. The List of PMOs can be found at:
14. How to share buoy data ?
Information on how to share buoy data and make data available to the WMO is available from the Data Buoy Cooperation Panel (DBCP) website at: https://www.ocean-ops.org/dbcp/data/sharing.html
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