12 Aug 2021

12 Aug 2021

Review status: this preprint is currently under review for the journal ACP.

Ozone deposition impact assessments for forest canopies require accurate ozone flux partitioning on diurnal timescales

Auke J. Visser1, Laurens N. Ganzeveld1, Ignacio Goded2, Maarten C. Krol1,3, Ivan Mammarella4, Giovanni Manca2, and K. Folkert Boersma1,5 Auke J. Visser et al.
  • 1Wageningen University, Meteorology and Air Quality Section, Wageningen, the Netherlands
  • 2Joint Research Centre, European Commission, Ispra, Italy
  • 3Utrecht University, Institute for Marine and Atmospheric Research Utrecht, Utrecht, the Netherlands
  • 4University of Helsinki, Institute for Atmospheric and Earth System Research/Physics, Helsinki, Finland
  • 5Royal Netherlands Meteorological Institute, R&D Satellite Observations, de Bilt, the Netherlands

Abstract. Dry deposition is an important sink of tropospheric ozone that affects surface concentrations, and impacts crop yields, the land carbon sink and the terrestrial water cycle. Dry deposition pathways include plant uptake via stomata and nonstomatal removal by soils, leaf surfaces and chemical reactions. Observational studies indicate that ozone deposition exhibits substantial temporal variability that is not reproduced by atmospheric chemistry models due to a simplified representation of vegetation uptake processes in these models. In this study, we explore the importance of stomatal and non-stomatal uptake processes in driving ozone dry deposition variability on diurnal to seasonal timescales. Specifically, we compare two land surface ozone uptake parameterizations – a commonly applied ’big leaf’ parameterization (W89; Wesely, 1989) and a multi-layer model (MLC-CHEM) constrained with observations – to multi-year ozone flux observations at two European measurement sites (Ispra, Italy, and Hyytiälä, Finland). We find that W89 cannot reproduce the diurnal cycle in ozone deposition due to a mis-representation of stomatal and non-stomatal sinks at our two study sites, while MLC-CHEM accurately reproduces the different sink pathways. Evaluation of non-stomatal uptake further corroborates the previously found important roles of wet leaf uptake in the morning under humid conditions, and soil uptake during warm conditions. The misrepresentation of stomatal versus non-stomatal uptake in W89 results in an overestimation of growing-season cumulative ozone uptake (CUO), a metric for assessments of vegetation ozone damage, by 18 % (Ispra) and 28 % (Hyytiälä), while MLC-CHEM reproduces CUO within 7 % of the observation-inferred values. Our results indicate the need to accurately describe the partitioning of the ozone atmosphere-biosphere flux over the in-canopy stomatal and non-stomatal loss pathways to provide more confidence in atmospheric chemistry model simulations of surface ozone mixing ratios and deposition fluxes for large-scale vegetation ozone impact assessments.

Auke J. Visser et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-670', Anonymous Referee #1, 23 Aug 2021
  • RC2: 'Comment on acp-2021-670', Anonymous Referee #2, 30 Aug 2021

Auke J. Visser et al.

Auke J. Visser et al.


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Short summary
Dry deposition is an important sink for tropospheric ozone that affects ecosystem carbon uptake, but process understanding remains incomplete. We apply a common deposition representation in atmospheric chemistry models and a multi-layer canopy model to multi-year ozone deposition observations. The multi-layer canopy model performs better on diurnal timescales compared to the common approach, leading to a substantially improved simulation of ozone deposition and vegetation ozone impact metrics.