Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Atmos. Chem. Phys., 18, 49-63, 2018
https://doi.org/10.5194/acp-18-49-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
03 Jan 2018
Observations of ozone depletion events in a Finnish boreal forest
Xuemeng Chen1, Lauriane L. J. Quéléver1, Pak L. Fung1, Jutta Kesti2, Matti P. Rissanen1, Jaana Bäck1, Petri Keronen1, Heikki Junninen1,3, Tuukka Petäjä1, Veli-Matti Kerminen1, and Markku Kulmala1 1Division of Atmospheric Sciences, Department of Physics, 00014 University of Helsinki, Finland
2Atmospheric Composition Research, Finnish Meteorological Institute, P.O. Box 503, 00101 Helsinki, Finland
3Institute of Physics, University of Tartu, Ülikooli 18, 50090 Tartu, Estonia
Abstract. We investigated the concentrations and vertical profiles of ozone over a 20-year period (1996–2016) at the SMEAR II station in southern Finland. Our results showed that the typical daily median ozone concentrations were in the range of 20–50 ppb with clear diurnal and annual patterns. In general, the profile of ozone concentrations illustrated an increase as a function of heights. The main aim of our study was to address the frequency and strength of ozone depletion events at this boreal forest site. We observed more than a thousand of 10 min periods at 4.2 m, with ozone concentrations below 10 ppb, and a few tens of cases with ozone concentrations below 2 ppb. Among these observations, a number of ozone depletion events that lasted for more than 3 h were identified, and they occurred mainly in autumn and winter months. The low ozone concentrations were likely related to the formation of a low mixing layer under the conditions of low temperatures, low wind speeds, high relative humidities and limited intensity of solar radiation.

Citation: Chen, X., Quéléver, L. L. J., Fung, P. L., Kesti, J., Rissanen, M. P., Bäck, J., Keronen, P., Junninen, H., Petäjä, T., Kerminen, V.-M., and Kulmala, M.: Observations of ozone depletion events in a Finnish boreal forest, Atmos. Chem. Phys., 18, 49-63, https://doi.org/10.5194/acp-18-49-2018, 2018.
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Short summary
We analysed a 20-year-long dataset collected in a Finnish boreal forest at SMEAR II station to investigate the frequency and strength of ozone depletion events. We could identify a number of ozone depletion events that lasted for more than 3 h, mainly in the autumn and winter months. Their occurrence was likely related to the formation of a low mixing layer under the conditions of low temperatures, low wind speeds, high relative humidities and limited intensity of solar radiation.
We analysed a 20-year-long dataset collected in a Finnish boreal forest at SMEAR II station to...
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