Site Description

SMEAR III is the urban station of the SMEAR (Stations for Measuring Ecosystem–Atmosphere Relations) network. It is on the Kumpula campus of the University of Helsinki (UHEL), about 4 km northeast of the city centre (60.2029° N, 24.9611° E). Continuous measurements began in autumn 2004. The aim was to extend the long term observations made at the SMEAR forest stations into a city, where human influence on the atmosphere is strongest (Järvi et al., 2009). The station is operated by INAR at UHEL together with the Finnish Meteorological Institute (FMI).

The site is an urban background location with varied surroundings. Depending on wind direction, the air arriving at the station passes over buildings, roads, or parks and woodland, so the station sees how urban emissions mix and change in the atmosphere. The measurements cover aerosol particle number size distributions from about 1–820 nm, aerosol optical properties and black carbon, trace gases and meteorology. It also measures turbulent fluxes of momentum, heat, water vapour, CO₂ and aerosol particles by eddy covariance. Data from the UHEL instruments at the station are openly available through SmartSMEAR. Data from the FMI instruments can be downloaded from the FMI Download observations service. Refer to the Instruments page to see which instruments are operated by UHEL and which by FMI.

Measurement Points

• Station container: UHEL instruments for aerosol particle number size distributions and trace gases, and FMI instruments for black carbon, aerosol scattering and particle mass.
• Supersite container: installed in 2026, currently with a volatile organic compound (VOC) gas chromatograph operated by FMI. It will soon host the station’s EU air quality monitoring supersite measurements, combining online instruments with offline filter sampling for particulate mass (PM10 and PM2.5), PM2.5 chemical composition, ultrafine particles, black carbon, nitrogen dioxide, ozone and ozone precursor VOCs.
• Mast: a 32 m tower with temperature profiles at 4, 8, 16 and 32 m; wind, radiation measurements, a condensation particle counter (CPC) for total particle number concentration, and eddy covariance at the top.
• Physicum roof: present weather, visibility and precipitation.

Research Infrastructures

ICOS: SMEAR III has been an Associated ICOS (Integrated Carbon Observation System) Ecosystem Station since November 2019, under station ID FI-Kmp. It is one of very few urban ecosystem stations in ICOS.

ACTRIS: SMEAR III is a candidate ACTRIS (Aerosol, Clouds and Trace Gases Research Infrastructure) observation site, and is currently going through the ACTRIS labelling process. The station is actively involved with the Cluster Calibration Center (CCC) of CAIS-ECAC. The CCC coordinates ACTRIS measurements of particles smaller than 10 nm and is hosted by INAR here on the Kumpula campus.

EU air quality supersite: SMEAR III is Finland’s urban background monitoring supersite under the revised EU Ambient Air Quality Directive (Directive (EU) 2024/2881). It is expected to be fully established in 2027.

Related Helsinki Sites

• Hotel Torni: eddy covariance flux measurements on the roof of Hotel Torni, a 69.5 m building in the city centre.
• Viikki: urban ecosystem and aerosol measurements on the Viikki campus, about 3 km northeast of Kumpula.
• Kumpula Botanic Garden (Kumpula puutarha): urban tree and soil measurements, including tree gas exchange and sap flow, soil temperature and moisture, and chamber measurements of CO₂ exchange.

Contact

Station manager: Tommy Chan (tommy.chan@helsinki.fi)
Data questions: atm-tech@helsinki.fi

References

Järvi, L., Hannuniemi, H., Hussein, T., Junninen, H., Aalto, P. P., Hillamo, R., Mäkelä, T., Keronen, P., Siivola, E., Vesala, T. and Kulmala, M. (2009). The urban measurement station SMEAR III: Continuous monitoring of air pollution and surface–atmosphere interactions in Helsinki, Finland. Boreal Environment Research 14 (Suppl. A), 86–109.