Articles | Volume 17, issue 2
Atmos. Chem. Phys., 17, 1361–1379, 2017

Special issue: Interactions between climate change and the Cryosphere: SVALI,...

Atmos. Chem. Phys., 17, 1361–1379, 2017

Research article 30 Jan 2017

Research article | 30 Jan 2017

Simulating ozone dry deposition at a boreal forest with a multi-layer canopy deposition model

Putian Zhou1, Laurens Ganzeveld2, Üllar Rannik1, Luxi Zhou1,a, Rosa Gierens1,b, Ditte Taipale3,4, Ivan Mammarella1, and Michael Boy1 Putian Zhou et al.
  • 1University of Helsinki, Department of Physics, P.O. Box 64, University of Helsinki, 00014 Helsinki, Finland
  • 2Meteorology and Air Quality (MAQ), Department of Environmental Sciences, Wageningen University and Research Centre, Wageningen, the Netherlands
  • 3University of Helsinki, Department of Forest Sciences, P.O. Box 27, University of Helsinki, 00014 Helsinki, Finland
  • 4Estonian University of Life Sciences, Department of Plant Physiology, 51014 Kreutzwaldi 1, Estonia
  • anow at: US Environmental Protection Agency, Research Triangle Park, NC, USA
  • bnow at: Institute for Geophysics and Meteorology, University of Cologne, Cologne, Germany

Abstract. A multi-layer ozone (O3) dry deposition model has been implemented into SOSAA (a model to Simulate the concentrations of Organic vapours, Sulphuric Acid and Aerosols) to improve the representation of O3 concentration and flux within and above the forest canopy in the planetary boundary layer. We aim to predict the O3 uptake by a boreal forest canopy under varying environmental conditions and analyse the influence of different factors on total O3 uptake by the canopy as well as the vertical distribution of deposition sinks inside the canopy. The newly implemented dry deposition model was validated by an extensive comparison of simulated and observed O3 turbulent fluxes and concentration profiles within and above the boreal forest canopy at SMEAR II (Station to Measure Ecosystem–Atmosphere Relations II) in Hyytiälä, Finland, in August 2010.

In this model, the fraction of wet surface on vegetation leaves was parametrised according to the ambient relative humidity (RH). Model results showed that when RH was larger than 70 % the O3 uptake onto wet skin contributed ∼ 51 % to the total deposition during nighttime and ∼ 19 % during daytime. The overall contribution of soil uptake was estimated about 36 %. The contribution of sub-canopy deposition below 4.2 m was modelled to be ∼ 38 % of the total O3 deposition during daytime, which was similar to the contribution reported in previous studies. The chemical contribution to O3 removal was evaluated directly in the model simulations. According to the simulated averaged diurnal cycle the net chemical production of O3 compensated up to ∼ 4 % of dry deposition loss from about 06:00 to 15:00 LT. During nighttime, the net chemical loss of O3 further enhanced removal by dry deposition by a maximum ∼ 9 %. Thus the results indicated an overall relatively small contribution of airborne chemical processes to O3 removal at this site.

Short summary
We implemented a multi-layer O3 dry deposition model in a 1-D model SOSAA to simulate O3 flux and concentration within and above a boreal forest at SMEAR II in Hyytiälä, Finland, in August 2010. The results showed that when RH > 70 % the O3 uptake on leaf wet skin was ~ 51 % to the total deposition at night and ~ 19 % at daytime. The sub-canopy contribution below 4.2 m was ~ 38 % at daytime. The averaged daily chemical contribution to total O3 alteration inside the canopy was less than 10 %.
Final-revised paper