Measurement stations in Kuopio
Experimental research for the Atmospheric Research Centre of Eastern Finland is carried out on three measurement stations: Puijo, Savilahti, and Vehmasmäki.
At Puijo the idea is 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, greenhouse gases, and meteorological parameters. The characteristic features are the elevated location (306 m above sea level, 224 m above surrounding lake level, on top of a 75 m tall observation tower standing on a 150 m high hill) in a semi-urban area (2 km northwest of the centre of Kuopio) and the site being frequently (approximately 15 % of the time) in cloud. The station is jointly operated by the Atmospheric Observations group and the Aerosol Physics group at the Department of Applied Physics of the Kuopio campus of University of Eastern Finland (UEF).
The measurements cover aerosol size distribution and number concentration, light extinction (scattering and absorption) by aerosol particles, cloud droplet size distribution, trace gas concentration, greenhouse gas concentration, and several meteorological parameters. The aerosol size distribution and optical properties are measured through two inlets: the interstitial, which removes cloud droplets and particles larger than 1.0 µm in diameter, and the total air inlet, which allows aerosol paticles and cloud droplets smaller than 40 µm in diameter to enter the sampling line. In the total air inlet the cloud droplets are dried and both the remaining residual and interstitial particles are measured. The difference between the total aerosol and interstitial aerosol gives then the fraction of activated particles as a function of particle size.
The Puijo measurement station is part of the SMEAR (Station for Measuring Ecosystem-Atmosphere Relations) network since 2009 and has provided ICOS (Integrated Carbon Observation System) compliant data since October 2020 (preceded by a demo experiment phase that started 2011).
The Savilahti site is at the Kuopio campus area of the UEF, approximately 2 km southwest from Puijo and approximately 2 km west from the center of Kuopio. The site is at the height of 87 m above sea level and 5 m above the surrounding lake level. At Savilahti, FMI has an automated weather station measuring several meteorological parameters, including the cloud base height measured with a ceilometer, and also instruments for measuring solar radiation. Observations of the weather and solar radiation in Savilahti can be accessed at data download site. In addition to the weather measurements, aerosol optical properties are measured by using a sun photometer that belongs to the AERONET (AErosol RObotic NETwork) network maintained by the US National Aeronautics and Space Association (NASA). Measurements of the direct solar radiation provide information to retrieve the columnar aerosol optical depth, while the sky radiance measurements can be inverted to produce aerosol optical properties such as size distribution, single scattering albedo, phase functions, and the complex index of refraction. Furthermore, the global solar radiation is measured with a pyranometer that belongs to the SolRad-Net (Solar Radiation Network) network implemented as a companion to AERONET and also maintained by NASA.
Vehmasmäki is located in a forested rural area about 20 km south from the city centre of Kuopio. The station was established next to a 318 m tall mast in 2012. We are studying atmospheric profiles of various aerosol particles and clouds with ground-based remote sensing instruments. The most recent topics have been pollen observations with lidars and atmospheric icing.
The main tool, also part of EARLINET, is a PollyXT multiwavelength Raman depolarization lidar. The so called “3+2+2+1” system is capable of measuring profiles of backscatter coefficient at three wavelengths (355, 532 and 1064 nm), extinction coefficient at two wavelengths and particle depolarization at two wavelengths. Additionally, profiles of water vapour mixing ratio can be retrieved. This information can be retrieved from about 100 m above ground level to few tens of kilometers, with a resolution of 7.5 m.
The tall mast provides a facility to study atmospheric icing which is an important topic as icing is causing operative problems for example for aviation and energy sector. Icing measurements are conducted at 115 and 272 m levels. The 318 m mast also is equipped with temperature and RH measurements at 7 different altitudes (2, 66, 115, 168, 215, 272 and 300m) and wind speed and direction are provided from 4 altitudes (26, 115, 215 and 272 m).
Supporting measurements include aerosol and wind profile measurements with a Halo Streamline Doppler lidar and aerosol/cloud profiling with Vaisala CL51 ceilometer. At ground-level aerosol total mass and size distributions, aerosol scattering coefficients, absorption coefficients and black carbon concentrations are measured. In addition, specific measurements of pollen are carried out during the pollen season. Present weather parameters, including visibility are also observed.