Published January 3, 2018
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Observations of ozone depletion events in a Finnish boreal forest
Authors/Creators
- 1. Division of Atmospheric Sciences, Department of Physics, 00014 University of Helsinki, Finland
- 2. Atmospheric Composition Research, Finnish Meteorological Institute, P.O. Box 503, 00101 Helsinki, Finland
- 3. Institute of Physics, University of Tartu, Ülikooli 18, 50090 Tartu, Estonia
Description
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.
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