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 Kulmala1Xuemeng Chen et al. 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
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
Received: 03 May 2017 – Discussion started: 22 Jun 2017 – Revised: 13 Oct 2017 – Accepted: 07 Nov 2017 – Published: 03 Jan 2018
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.
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...
