Östergarnsholm field station

On the island Östergarnsholm located about 2 nautical miles off the east coast of Gotland a 30 m micrometeorological tower was established in 1995 on the most southern tip of the island.  The measurement station consists of anemometers, temperature and humidity sensors as well as sophisticated instrumentation for measuring gas exchange of carbon dioxide and other scalars between the sea and the atmosphere.

In addition to measurements in the mast, the conditions in the water are also measured with several types of instruments (see Figure 1) as part of Östergarnsholm's field station becoming part of the Integrated Carbon Observation System (ICOS) in 2015 as a Fixed Ocean Station (FOS). The purpose of this Swedish marine ICOS station is to collect data to study processes that control how the ocean and atmosphere interact and exchange gases between them.

Figure 1: Schematic of water-side buoy system located about 1 km from the measurement tower.

The ICOS station at Östergarnsholm acts as a unique marine measurement site open to researchers from Europe and other parts of the world to come and visit and perform measurements with their own instruments. An example of the use of the station's infrastructure was in connection with measurements of gas exchange of mercury between sea and atmosphere from which the picture below (Figure 2) was taken of the 30 m measuring mast below and a 10 m measuring mast operated by Stockholm University for exchange as aerosols. Since the station's establishment, a long-term collaboration between Uppsala University and the Finnish Meteorological Institute (FMI) has also been carried out with studies of ocean surface waves in the Baltic Sea with measurements from a wave buoy located approximately 4 km from the field station.

Figure 2: Photograph of the 30 m main measurement tower maintained by Uppsala University since 1995 and also a smaller 10 m tower instrumented for studying aerosol fluxes and air-sea exchange operated by Stockholm University.

The station operated by Uppsala University is used in connection with a number of associated or independent surveys where a number of different measurement techniques have been used for specific field visits or for semi-continuous or more continuous measurements. These include radiosoundings and drone measurements (Figure 3), water sampling and analysis of carbon dioxide and methane (Figure 4), measurements of currents, turbulence and waves with Acoustic Doppler Current Profiles (ADCP) (Figure 5), wind profiles and turbulence up to about 250 m altitude with wind lidar (Figure 6), precipitation and droplet size distributions with distrometer (Figure 7) and clouds using ceilometer (Figure 8).

Figure 3: During a field campaign and maintenance week simultaneous radiosounding and drone measurements was conducted.
Figure 4: Researchers and PhD students working on analysis of water samples taken at the site for quantification and validation of carbon dioxide and methane concentration in the Baltic Sea.

Figure 5: Photograph from the deployment of an Acoustic Doppler Current Profiler (ADCP) about one kilometer from Östergarnsholm.
Figure 6: Photograph of a wind lidar measuring wind profile and turbulence in the atmosphere up to about 250 m height for basic research and wind energy related projects.
Figure 7: Photograph of the distrometer measuring precipitation and droplet size distributions.
Figure 8: Photograph of the ceilometer measuring clouds and hydrometeors up to 6500 m.

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