Preprints
https://doi.org/10.5194/acp-2022-697
https://doi.org/10.5194/acp-2022-697
27 Oct 2022
 | 27 Oct 2022
Status: a revised version of this preprint was accepted for the journal ACP and is expected to appear here in due course.

Simulation of organic aerosol, its precursors and related oxidants in the Landes pine forest in south-western France: Need to account for domain specific land-use and physical conditions

Arineh Cholakian, Matthias Beekmann, Guillaume Siour, Isabelle Coll, Manuela Cirtog, Elena Ormeno, Pierre-Marie Flaud, Emilie Perraudin, and Eric Villenave

Abstract. Organic aerosol (OA) still remains one of the most difficult components of the atmospheric aerosols to simulate, given the multitude of its precursors, the uncertainty of its formation pathways and the lack of measurements of its detailed composition. The LANDEX project (The LANDes Experiment), during its intensive field campaign in summer 2017, gives us not only the opportunity to compare biogenic secondary OA (BSOA), but also its precursors and oxidants obtained within and above the Landes forest canopy, to simulations performed with CHIMERE, a state of the art regional Chemistry-Transport Model. The Landes forest is situated in the south-western part of France, and is one of the largest anthropized forests in Europe (1 million ha), composed by a majority of maritime pine trees, strong terpenoid emitters, providing a large potential for biogenic SOA formation. In order to simulate OA build-up in this area, a specific model configuration set-up, adapted to the local peculiarities was necessary. As the forest is inhomogeneous, with interstitial agricultural fields, high-resolution 1 km simulations over the forest area were performed. BVOC emissions were predicted by MEGAN, but specific land cover information needed to be used, chosen from the comparison of several high-resolution land cover databases. Moreover, the tree species distribution needed to be updated for the specific conditions of the Landes forest. In order to understand the canopy effect in the forest, canopy effects on vertical diffusivity, winds and radiation were implemented in the model in a simplified way. The refined simulations show a redistribution of BVOCs with a decrease in isoprene and an increase in terpenoid emissions with respect to the standard case, in line with observations. Corresponding changes on simulated BSOA sources are tracked. Very low night-time ozone, sometimes near zero, remains overestimated in all simulations. This has implications to the night-time oxidant budget, including NO3. Despite careful treatment of physical conditions, simulated BSOA is overestimated in the most refined simulation. Simulations are also compared to air quality sites surrounding the Landes forest, reporting a more realistic simulation in these stations in the most refined test case. Finally the importance of the see breeze system which also impacts species concentrations inside the forest is made evident.

Arineh Cholakian et al.

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2022-697', Anonymous Referee #1, 12 Dec 2022
  • RC2: 'Comment on acp-2022-697', Anonymous Referee #2, 06 Jan 2023
  • AC1: 'Comment on acp-2022-697', Arineh Cholakian, 21 Feb 2023

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2022-697', Anonymous Referee #1, 12 Dec 2022
  • RC2: 'Comment on acp-2022-697', Anonymous Referee #2, 06 Jan 2023
  • AC1: 'Comment on acp-2022-697', Arineh Cholakian, 21 Feb 2023

Arineh Cholakian et al.

Arineh Cholakian et al.

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Short summary
This article revolves around the simulation of biogenic secondary organic aerosols in the Landes forest (south-west France). In order to do so, several sensitivity cases involving biogenic emission factors, landcover data, anthropogenic emissions and physical parameters were performed and each compared to measurements both in the forest canopy and around the forest. The chemistry behind the formation of these aerosols and their production and transport in the forest canopy are discussed.
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