VOS Ships Evolution 2003-2006
Ville de Bordeaux
Two categories of VOS ships are considered by the programme: “manned VOS” and shipborne Automated Weather Stations (AWS). Fixed platforms such as moored buoys or oil rigs reporting FM-13 SHIP messages onto the GTS are presently excluded. The first category of VOS is composed of ships on which crew officers are reading instruments and report their data as well as visual observations through the GMDSS Inmarsat transmitter of these ships. The data are primarily coded thanks to a dedicated software such as TurboWin.
TurboWin, developed by KNMI, has been recognized by E-SURFMAR participants as being essential for manned VOS. The most recent version includes a new procedure for unambiguous input of the barometer reading, add-ons for additional (WMO Pub-47) data and extended phenomena descriptions. E-SURFMAR recommends its installation or upgrade on all EUMETNET VOS ships who are not equipped with an AWS.
AWS carry out basic measurements – air pressure, sea surface temperature, air temperature and humidity, wind direction and velocity – at regular intervals (hourly or 3-hourly) and send the data automatically. Most of the AWS allow crew officers to enter their visual observations before transmission, if they wish.
Data availability
During 2003-2006, EUMETNET VOS reported approximately 47% of the manned VOS observations carried out in the world and 58% of the AWS observations. Figures 1 and 2 show the mean number of air pressure observations reported by EUMETNET VOS from the EUCOS area of interest every day. One can see the number of observations reported by manned VOS dropped from approximately 400 observations per day in 2003 to less than 300 by the beginning of 2006 although the number of daily observations received from AWS increased from 300 to more than 450 during the same period (550 in April 2006).
Automation
The growth of automation to measure the basic surface marine parameters is strongly encouraged by E-SURFMAR. The BATOS AWS system developed by Météo-France seems to be well adapted to the programme.
The system was upgraded and made available to the E-SURFMAR participants. Although these latest may purchase their own BATOS systems to equip their ships for national purposes, E-SURFMAR funded three systems in 2005 for the purposes of the programme and five others in 2006.
A Memorandum of Understanding (MoU) between Meteo-France and volunteer operators was prepared. It covers both cases : the use of BATOS systems funded by E-SURFMAR and those directly purchased by the operators.
The UK Met Office is evaluating a number of AWS from different manufacturers (e.g AVOS, AutoMet, MINOS and BATOS, etc). The results of this evaluation will help to inform E-SURFMAR decisions concerning the most suitable automatic systems for use in the future.
Data transmission
Thanks to a compression technique, it is allowed to report hourly observations at a reasonable price. For the record, a text report presently sent through the GMDSS transmitter of the ship (e.g. to SAC 41) costs approximately 1.00 €.
The compression technique used to report AWS data can not be applied to Inmarsat GMDSS transmitters. However, a half compression technique could be used to reduce the transmission costs for manned VOS. Meteo-France and KNMI are working together to test this technique on a few ships. The TurboWin software is enhanced to compress the ship data and to make them ready to be transmitted (in ASCII) through the GMDSS transmitter of the ship. Meteo-France is developing the decoding software at the receiving centre. Communication costs should be divided by 2.5 approximately (60% savings). The results of the tests should be available in March 2007.
In parallel, the use of Iridium (Short Burst Data service) was tested in 2006 as an alternative communication system for AWS. The transmission of a report costs 0.08 € approximately.
Data quality
Carmen
Since the E-SURFMAR design study was issued, air pressure data reported by EUMETNET ships into the EUCOS area have been monitored as a matter of priority. Clearly, the quality of measurements carried out by “manned” VOS is presently worse than this of AWS.
The main problem is due to ships on which the air presure is sometimes uncorrected or double corrected from the height of the barometer. The new procedure implemented in TurboWin to warn observers about barometer reading, should improve the quality of air pressure data reported by manned VOS. However, it will take a while before all ships have their software upgraded.