09 Oct 2023
 | 09 Oct 2023
Status: this preprint is open for discussion.

Evaluation of isoprene emissions from the coupled model SURFEX-MEGANv2.1

Safae Oumami, Joaquim Arteta, Vincent Guidard, Pierre Tulet, and Paul Hamer

Abstract. Isoprene, a key biogenic volatile organic compound, plays a pivotal role in atmospheric chemistry. Due to its high reactivity, this compound contributes significantly to the production of tropospheric ozone in polluted areas, and to the formation of secondary organic aerosols.

The assessment of biogenic emissions is of great importance for regional and global air quality evaluation. In this study, we have implemented the biogenic emissions model MEGANv2.1 (Model of Emission of Gases and Aerosols from Nature, version 2.1) in the surface model SURFEXv8.1 (SURface EXternalisée in french, version 8.1). This coupling aims to improve the estimation of biogenic emissions using the detailed vegetation type-dependent treatment included in the SURFEX vegetation ISBA scheme. This scheme provides to MEGAN vegetation-dependent parameters allowing a more precise estimation of biogenic fluxes (e.g., leaf area index, soil moisture, wilting point data).

The present study focuses on the assessment of the SURFEX-MEGAN model isoprene emissions. The evaluation of the coupled SURFEX-MEGAN model results was carried out by conducting a global isoprene emissions simulation in 2019 and comparing the simulation results with other MEGAN-based isoprene inventories. The coupled model estimates a total global isoprene emission of 442 Tg in 2019. The estimated isoprene is within the range of results obtained with other MEGAN-based isoprene inventories, ranging from 311 Tg to 637 Tg. The spatial distribution of SURFEX-MEGAN isoprene is consistent with other studies, with some differences located in low isoprene emission regions.

Several sensitivity tests were conducted to quantify the impact of different model inputs and configurations on isoprene emissions. Using different meteorological forcings resulted in a +/-5 % change in isoprene emission using MERRA and IFS, respectively, compared with ERA5. The impact of using different emission factors data was also investigated. The use of PFT spatial coverage and PFT-dependent emission potential data resulted in a 14 % reduction compared to using the isoprene emission potential gridded map. A significant reduction of around 38 % in global isoprene emissions, was observed in the third sensitivity analysis, which applied a parameterization of soil moisture deficit, particularly in certain regions of Australia, Africa and South America.

The significance of coupling the SURFEX and MEGAN models lies particularly in the ability of the coupled model to be able to be forced with meteorological data from any time period. This means, for instance, that this system can be used to predict biogenic emissions in the future. This aspect of this work is significant given the changes that biogenic organic compounds are expected to undergo as a result of changes in their climatic factors.

Safae Oumami et al.

Status: open (until 04 Dec 2023)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-2206', Anonymous Referee #1, 31 Oct 2023 reply
  • RC2: 'Comment on egusphere-2023-2206', Anonymous Referee #2, 13 Nov 2023 reply
  • CEC1: 'Comment on egusphere-2023-2206', Juan Antonio Añel, 19 Nov 2023 reply
    • AC1: 'Reply on CEC1', Safae Oumami, 28 Nov 2023 reply
      • CEC2: 'Reply on AC1', Juan Antonio Añel, 28 Nov 2023 reply
        • AC2: 'Reply on CEC2', Safae Oumami, 29 Nov 2023 reply

Safae Oumami et al.

Safae Oumami et al.


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Short summary
In this paper, we have coupled the SURFEX and MEGAN models. The aim of this coupling is to improve the estimation of biogenic fluxes by using the SURFEX canopy environment model. The coupled model results were validated and several sensitivity tests were performed. The coupled model total annual isoprene flux is 442 Tg, this value is within the range of other reported isoprene estimates. The ultimate aim of this coupling is to predict the impact of climate change on biogenic emissions.