What a Saildrone Measures
Learn the various types of measurements scientists are working to validate with Saildrone
29 April - ITAE has several researchers working with the data collected during this project. From data transmissions received via email, we’ve used processing software to generate maps and time series (data over a period of time) of atmospheric and oceanic data that the Saildrones record. These maps are updated daily when the files are received. We have two Saildrones operating during this project - referred to as numbers 128 and 126.
Saildrones measure and report back, via an Iridium satellite data link, their position (latitude and longitude), atmospheric parameters (barometric pressure, wind, air temperature, relative humidity and sunlight) and oceanic parameters (red-light backscatter, chlorophyll-a concentration, dissolved oxygen concentration, water temperature, salinity, colored dissolved organic matter, ocean surface current, and magnetic field strength).
What does this data tell us? The position data allow scientists to plot measurements on a map. Barometric pressure and wind speed are indicators of storms and mixing of the ocean’s upper layers, as well as fair or foul weather that affects Saildrone sailing conditions. Air temperature and humidity tell whether it is warm or cold, perhaps owing to the proximity of sea ice – something Saildrones must stay away from to avoid hull damage. Sunlight provides energy to top-up Saildrone batteries and to grow microscopic plants or phytoplankton – the basis of the oceanic food web. Measurement of the amount of sunlight scattered back to the sky in the red color band is used to calibrate satellite measurements that can deduce ocean properties from high above. The chlorophyll-a concentration is a direct measure of how much phytoplankton are present. The dissolved oxygen concentration measures their ability to transform inorganic material – nutrients and carbon dioxide – into plant biomass consumed and passed up the food web to larger animals, including zooplankton, crab, fish, whales and humans. Water temperature and salinity govern the basic physical conditions of the oceanic ecosystem. Colored dissolved organic matter (CDOM) is a tracer of river water that has entered the ocean. Ocean currents transport water and passive plankton to new locales. Magnetic field signatures show variations in the earth’s magnetic field and provide information on seafloor spreading.
Kim Martini (JISAO) shares three samples of Saildrone data with us; wind, temperature, and salinity. The display of the data is broken into three parts. First, on the right side, is a map of the Bering Sea and the track of the Saildrone (in orange) since it was deployed from Dutch Harbor, AK in the Aleutian Islands on April 23, 2015. Second, the map on the left side is a zoomed-in map, showing wind speed (color) and direction (arrows) as measured by Saildrone No. 128. Third, in the bottom right is the time series of wind speed (blue) and wind gusts (pink) over the course of the deployment.
WIND is measured in knots and is referred to by the direction from which the wind is blowing.
TEMPERATURE is measured in Celsius of the first several meters of the waters surface.
SALINITY is measured in Practical Salinity Units (PSU) and measures the saltiness or dissolved salt content of a body of water.