Ship based measurements - SOT


Brief history:

Ships play a key role in atmospheric, oceanic and biogeochemical observations. Since the days when sailing vessels were the primary vehicle for commerce and exploration on the high seas, 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 quality in-situ data. Every day, 2,000 voluntary ships (merchant ships, ferries, fishing vessels, sailing yachts) around the world 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 observing ships provide hourly 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
  • Direction
  • Sea state
  • Humidity
  • Visibility
  • Air and sea surface temperature
  • Etc.


Societal applications: 
  • Marine forecasts and 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. temperature, salinity, ocean carbon, etc.) in many different ways.

In this section we only describe an eXpendable BathyThermograph (XBT) that provides the simplest and most cost-efficient solution for frequently obtaining 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 (to ~1,000 m depth)

An XBT is a temperature probe that is launched from the bridge wing of a ship using a hand or automatic launcher. The probes are launched by ship personnel 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, and government laboratories for weather and climate forecasting and 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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