Sand at sea, as seen from space

By Mark Higgins (EUMETSAT) and Sancha Lancaster (Blue Monday)

This project was a partnership between EUMETSAT and the national weather services of Germany (DWD), Austria (ZAMG) and Portugal (IPMA), and theAlfred Wegener Institute for Polar and Marine Research (AWI), the operator of the research vessel. DWD followed the ship with two classes of students in weather forecasting and observing at the Deutscher Wetterdienst (DWD) training school in Langen, Germany.

Throughout the expedition EUMETrain’s Polarstern portal allowed users to monitor the track of the vessel while comparing the ship’s data with satellite-derived products, images and model fields from DWD. So the users will have the opportunity to hone their skills in:

• interpretation of satellite images and products, including wind information and altimetry;
• interpretation of radio soundings and synops (FM13 Ship);
• interpretation of NWP-products;
• the format of the different climate zones.

Polarstern meteorological monitoring research

Polarstern was well-equipped for meteorological research, as well as for routine meteorological services. Data from a number of measuring systems and sensors — including the navigation system and sensors from the meteorology, oceanography, bathymetry, and chemistry — were stored by the DSHIP (formerly PODAS) data acquisition system.

The data were sampled every second as non-validated raw-data in physical units. The meteorological observatory was permanently manned with a weather observer from DWD, who performed the three-hourly synoptic observations (during night time — when the weather observer was not on duty — they were performed automatically) and the daily upper air soundings. Upper air soundings included profile measurements of pressure, temperature, relative humidity and wind vector.

For this cruise there was also be a forecaster on-board, whose role was to advise the captain and all scientists on any weather-related questions.

Data from EUMETSAT included satellite images, significant wave height (from altimeters) and wind speed and direction (from scatterometers).

On 11 April ship was cruising from Punta Arenas (Chile) to Bremerhaven (arriving 16 May), taking continuous measurements of atmospheric and marine properties, plus energy and material fluxes between ocean and atmosphere.

When the Polarstern crossed the equator on its journey to Bremerhaven, the weather was been calm, but the skies were not clear. Saharan sand was carried out to sea by an African easterly jet, a specific type of wind pattern.

The dust was 1,500 to 6,000m above the ground and at sea it lead to reduced visibility (about 4km). As well as witnessing the reduction in visability, meteorologists on board the ship discovered deposits of sand on deck (Figure 2).

This dust could be seen clearly from space, showing up as pink in image on the right (top).

The image was produced using a particular set of channels from the MSG satellite, these channels are sensitive to dust in the atmosphere.

The dust can also be seen in the visible image (bottom) as a brown haze over the ocean.

EUMETSAT trainer Mark Higgins, who had been tracking Polarstern, said: "This small amount of dust is not a hazard for the ship, but it shows that we are able to get information about small airborne particles from the satellite data.

"This allows us to track dust storms (hazardous for people) over land or volcanic ash (a hazard for aircraft) in the air."

This project was a partnership between EUMETSAT and the national weather services of Germany (DWD), Austria (ZAMG) and Portugal (IM), and the Alfred Wegener Institute for Polar and Marine Research (AWI), the operator of the research vessel.

EUMETSAT’s international training project EUMETrain tracked the ship via a special Polarstern portal.

Safety at sea

The primary role of a marine weather forecaster is safety — providing information and warnings to people who work at sea or in coastal areas. Satellite information is crucial in diagnosing the atmosphere forecasting hazards. Sea captains depend on the advice of marine weather forecasters so that they can steer away from large storms.

This portal follows the journey of a real ship and crew. It is a tangible example of the practical nature of weather forecasting at sea, the reports from the onboard meteorologist will tell the story of life aboard and the connection between the weather and working at sea.

The weather forecasts are also very important for the transaction of the different scientific experiments aboard Polarstern.

Polarstern facts

• RV Polarstern (meaning pole star) is a German research icebreaker of the Alfred Wegener Institute for Polar and Marine Research in Bremerhaven. The Polarstern was commissioned in 1982 and is mainly used for research in the Arctic and Antarctica.
• Polarstern is a double-hulled icebreaker. It is operational at temperatures as low as -50°C. (-58°F) Polarstern can break through ice 1.5m (4ft 11in) thick at a speed of 5 knots.
• Polarstern spend 320 days a year at sea.
• It has been the working place for more than 7,000 scientists from more than 35 nations.
• There are nine laboratories and room for 50 scientists onboard.
• Polarstern was built by the Howaldtswerke-Deutsche Werft at Kiel and the Nobiskrug at Rendsburg. The ship has a length of 118m (387ft).