• Main site: 61.850°N 24.283°E 181 m a.s.l.
• Tower: 61.850°N 24.283°E 216 m a.s.l.
• Radar field: 61.844°N 24.287°E 150 m a.s.l.

Observational platform

Finland

• University of Helsinki (UH)

https://www.atm.helsinki.fi/SMEAR/index.php/smear-ii

• Tuukka Petäjä
  Facility PI

The SMEAR II (Station for Measuring Ecosystem-Atmosphere Relations) is a ground-based fixed, observational platform, rural background site. SMEAR II started its operation in 1995, with an extensive range of measurement interests. The station is situated in a 60-year-old (in 2022) rather homogenous Scots pine stand on a flat terrain at Hyytiälä Forestry Field Station of the University of Helsinki 220 km North-West from Helsinki. The station represents a boreal coniferous forest that covers 8% of the Earth’s surface and stores about 10% of the total carbon in the terrestrial ecosystem.
Publication that describes the facility:
Hari, P., & Kulmala, M. (2005). Station for Measuring Ecosystem-Atmosphere Relations (SMEAR II). Boreal Environment Research, 10(5), 315-322.
Other key publications:
Neefjes, I., et al. (2022). 25 years of atmospheric and ecosystem measurements in a boreal forest — Seasonal variation and responses to warm and dry years. Boreal Environment Research, 27, 1-31.

SMEAR II is a Station for Measuring Ecosystem-Atmosphere Relations. SMEAR II produces comprehensive, simultaneous measurements on atmosphere, Earth surface and biosphere, covering meteorology, atmospheric composition and fluxes, as well as ecosystem variables. SMEAR II is a co-located ICOS, ACTRIS and eLTER site. The site contributes to ACTRIS aerosol in situ and reactive trace gases in situ measurements and cloud remote sensing. Using SMEAR II data, processes and phenomena related to biosphere-aerosol-cloud-climate feedback, particle gas-to-particle conversion, biogeochemical cycles and surface-atmosphere exchange of energy and greenhouse gases are investigated.

SMEAR II is operational 24/7, year round. On-site accommodation and support is in place. We provide e.g., open access to comprehensive multidisciplinary SMEAR II data, technical help and instrument monitoring and maintenance for observations during extended periods and support for research planning.

• Petäjä et al. (2021). Influence of biogenic emissions from boreal forests on aerosol–cloud interactions. Nat. Geosci., 15(1), 42-47. https://doi.org/10.1038/s41561-021-00876-0
• Nieminen et al. (2014). Trends in atmospheric new-particle formation: 16 years of observations in a boreal-forest environment. https://hdl.handle.net/10138/228760
• Chen et al. (2021). A modelling study of OH, NO₃ and H₂SO₄ in 2007–2018 at SMEAR II, Finland: analysis of long-term trends. Environ. Sci.: Atmos., 1(6), 449-472. https://doi.org/10.1039/D1EA00020A
• Sulo et al. (2021). Long-term measurement of sub-3 nm particles and their precursor gases in the boreal forest. Atmos. Chem. Phys., 21(2), 695-715. https://doi.org/10.5194/acp-21-695-2021
• Luoma et al. (2019). Over a 10-year record of aerosol optical properties at SMEAR II. Atmos. Chem. Phys., 19(17), 11363-11382. https://doi.org/10.5194/acp-19-11363-2019
• Heikkinen et al. (2020). Long-term sub-micrometer aerosol chemical composition in the boreal forest: inter- and intra-annual variability. Atmos. Chem. Phys., 20(5), 3151-3180. https://doi.org/10.5194/acp-20-3151-2020
• Li et al. (2021). Two-year statistics of columnar-ice production in stratiform clouds over Hyytiälä, Finland: environmental conditions and the relevance to secondary ice production. Atmos. Chem. Phys., 21(19), 14671-14686. https://doi.org/10.5194/acp-21-14671-2021