In Scandinavia and other northern lands, boreal forests produce gases that contribute to particle formation. In the atmosphere, these particles can influence cloud properties and, by extension, the climate.
Analyzing data gathered in a Finnish forest, an international team of researchers found that boreal forests might be able to moderate earth system changes across a continent. This work appeared in the January 2022 issue of Nature Geoscience.
Data in the paper came from the 2014 Biogenic Aerosols – Effects on Clouds and Climate (BAECC) field campaign. For almost eight months, the Atmospheric Radiation Measurement (ARM) user facility conducted BAECC in a Scots pine forest in Hyytiälä, Finland.
ARM instruments operated next to the Station for Measuring Ecosystem-Atmosphere Relations II (SMEAR II), managed by the University of Helsinki. ARM’s aerosol and remote-sensing data complemented SMEAR II’s long-term aerosol measurements. (SMEAR II data collection began in 1996.)
The paper’s lead author is Tuukka Petäjä, a University of Helsinki professor who led the BAECC campaign. BAECC work received support through the U.S. Department of Energy’s Atmospheric System Research (ASR).
Petäjä and his co-authors wanted to know how gases from boreal forests might affect the aerosol population, cloud and rain properties, and aerosol-cloud interactions. The team chose to study these effects in air masses originally from the Arctic Ocean. This was to reduce the influence of emissions from human activities.
One to three days after the clean marine air moved into the forest, scientists saw an increase in aerosol concentration in the lower boundary layer. This increase tracked with the quantity of new particles formed in the forest. In addition, the team noted that the new particles plus water vapor from the forest affected the reflectivity of warm, low-level clouds. When pieced together, this information indicates that boreal forests could affect climate on a continental scale.
For other continental areas with sources of gaseous emissions like those from boreal forests, the authors say that even small changes in those emissions could have big effects on cloud properties in moderately polluted environments.