Ship based measurements - SOT


Brief history:

Since the days when sailing vessels were the primary vehicle for commerce and exploration, ships have observed the marine environment.

Today, all types of ships make routine weather and ocean observations that are shared internationally to support research, climate forecasting, numerical weather prediction and maritime safety services amongst other applications.

Ships-based observations include meteorological and oceanographic measurements acquired under the umbrella of the Ship Observations Team (SOT) network.


Ship-based meteorological observations

Good forecasting of conditions at sea (wind, waves, current, etc.) make navigation safer and cheaper. However, such forecasts rely heavily on good quality of in-situ data. Every day, 2,000 voluntary ships - including merchant ships, ferries, fishing vessels, sailing yachts, etc. - moving around the world ocean, observe the weather at their location. Participating National Meteorological Services recruit these ships whose officers and staff are encouraged to record and transmit weather observations with loaned instruments. Today, an increasing number of Automatic Weather Stations installed on ships provide hourly meteorological data.

These data are transmitted in near real-time over satellite and then made available to users around the world. The data are also archived for future use by climatologists and other scientists.

A small number of merchant ships launching weather balloons also provide reliable marine upper-air data in a cost-effective way. These profile data are all made available to users around the world in real-time.

 Main data collected:
  • Air pressure
  • Wind speed and direction
  • Sea state
  • Humidity
  • Visibility
  • Air and sea surface temperature
  • Etc.
 Societal applications: 
  • Marine forecasts and early warnings
  • Monitoring the ocean state
  • Monitoring changes in the earth's climate


Ship-based oceanographic observations 

Ships also contribute to collect key oceanographic data (e.g. sea temperature, salinity, ocean carbon, etc.) in many different ways.

In this section we only describe an eXpendable BathyThermograph (called XBT) that provides the simplest and most cost-efficient solution for frequently  temperature profiles along fixed transects of the upper thousand meters of the ocean. The first XBT probes were tested in 1959, and systematic deployment of XBTs began in the mid to late 1960s. XBTs thus provide one of the longest available historical records of upper ocean temperature profiles.

An XBT is a temperature probe that is launched manually from the bridge wing of a ship or using an automatic launcher. The probes are launched 4 to 6 times per day. The data are logged to a computer where it is processed and formatted for satellite transmission in real-time through the Global Telecommunications System (GTS). The data are then used by national and international organizations, universities, research instituts for weather and climate forecasting as well as for climate research.

Data collected by an XBT:

Upper ocean thermal data

Societal applications:

XBTs provide vital observations to estimate the heat contained in the upper ocean and the surface currents which drive the sea surface temperatures. The understanding of the upper ocean temperatures provided by XBT observations is critical for better forecasts of marine weather and operations.


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