• 62.900°N 27.650°E 306 m a.s.l.

Observational platform

Finland

• Finnish Meteorological Institute (FMI)
• University of Eastern Finland (UEF)

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

• Annele Virtanen
  Facility PI
• Mika Komppula
  PI deputy

The SMEAR IV is located approximately 2 km northwest from the center of Kuopio on the top of an observation tower on Puijo hill. The station is at semi-urban environment and the surrounding vegetation represent boreal forest environment. Measurements are made at the height of 306 m above sea level and 230 m above the surrounding lake level. The measurements cover aerosol size distribution and number concentration, light extinction (scattering and absorption) by aerosol particles, cloud droplet size distribution, trace gas concentration, and several meteorological parameters. The aerosol size distribution is measured through two inlets: the interstitial, which removes the cloud droplets and particles smaller than 2.0 µm in diameter, and the total air inlet, which allows aerosol paticles and cloud droplets to enter the sampling line. In the total air inlet the cloud droplets are dried.

At SMEAR IV the idea is 1) to study and collect long time series of atmospheric composition (aerosols, trace gases etc) originated from different airmass sources as well as from local sources 2) to study the interactions of aerosol particles and clouds, especially the activation of aerosol particles into cloud droplets. The instrumentation covers measurement of aerosol dynamics, cloud droplet properties, optical measurements, trace gases and meteorological parameters. The characteristic features at SMEAR IV are the elevated location in a semi-urban area and the site being frequently in cloud.

• Portin et al. (2014). The effect of local sources on particle size and chemical composition and their role in aerosol–cloud interactions at Puijo measurement station. Atmos. Chem. Phys., 14(12), 6021-6034. https://doi.org/10.5194/acp-14-6021-2014
• Calderón et al. (2022). Aerosol–stratocumulus interactions: towards a better process understanding using closures between observations and large eddy simulations. Atmos. Chem. Phys., 22(18), 12417-12441. https://doi.org/10.5194/acp-22-12417-2022
• Ruuskanen et al. (2021). Observations on aerosol optical properties and scavenging during cloud events. Atmos. Chem. Phys., 21(3), 1683-1695. https://doi.org/10.5194/acp-21-1683-2021
• Väisänen et al. (2016). In-cloud measurements highlight the role of aerosol hygroscopicity in cloud droplet formation. Atmos. Chem. Phys., 16(16), 10385-10398. https://doi.org/10.5194/acp-16-10385-2016
• https://doi.org/10.5194/acp-14-13483-2014, 2014
• Hao et al. (2013). Aerosol Chemical Composition in Cloud Events by High Resolution Time-of-Flight Aerosol Mass Spectrometry. Environ. Sci. Technol., 47(6), 2645-2653. https://doi.org/10.1021/es302889w