Global biogenic volatile organic compound emissions in the ORCHIDEE and MEGAN models and sensitivity to key parameters
A new version of the biogenic volatile organic compounds (BVOCs) emission scheme has been developed in the global vegetation model ORCHIDEE (Organizing Carbon and Hydrology in Dynamic EcosystEm), which includes an extended list of biogenic emitted compounds, updated emission factors (EFs), a depe...
| Main Authors: | , , , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2016-11-01
|
| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/16/14169/2016/acp-16-14169-2016.pdf |
| Summary: | A new version of the biogenic volatile organic compounds (BVOCs) emission
scheme has been developed in the global vegetation model ORCHIDEE (Organizing
Carbon and Hydrology in Dynamic EcosystEm), which includes an extended list
of biogenic emitted compounds, updated emission factors (EFs), a dependency
on light for almost all compounds and a multi-layer radiation scheme. Over
the 2000–2009 period, using this model, we estimate mean global emissions of
465 Tg C yr<sup>−1</sup> for isoprene, 107.5 Tg C yr<sup>−1</sup> for monoterpenes,
38 Tg C yr<sup>−1</sup> for methanol, 25 Tg C yr<sup>−1</sup> for acetone and
24 Tg C yr<sup>−1</sup> for sesquiterpenes. The model results are compared to
state-of-the-art emission budgets, showing that the ORCHIDEE emissions are
within the range of published estimates. ORCHIDEE BVOC emissions are compared
to the estimates of the Model of Emissions of Gases and Aerosols from Nature
(MEGAN), which is largely used throughout the biogenic emissions and
atmospheric chemistry community. Our results show that global emission
budgets of the two models are, in general, in good agreement. ORCHIDEE
emissions are 8 % higher for isoprene, 8 % lower for methanol, 17 %
higher for acetone, 18 % higher for monoterpenes and 39 % higher for
sesquiterpenes, compared to the MEGAN estimates. At the regional scale, the
largest differences between ORCHIDEE and MEGAN are highlighted for isoprene
in northern temperate regions, where ORCHIDEE emissions are higher by
21 Tg C yr<sup>−1</sup>, and for monoterpenes, where they are higher by 4.4 and
10.2 Tg C yr<sup>−1</sup> in northern and southern tropical regions compared to
MEGAN. The geographical differences between the two models are mainly
associated with different EF and plant functional type (PFT) distributions,
while differences in the seasonal cycle are mostly driven by differences in
the leaf area index (LAI). Sensitivity tests are carried out for both models
to explore the response to key variables or parameters such as LAI and
light-dependent fraction (LDF). The ORCHIDEE and MEGAN emissions are
differently affected by LAI changes, with a response highly depending on the
compound considered. Scaling the LAI by a factor of 0.5 and 1.5 changes the
isoprene global emission by −21 and +8 % for ORCHIDEE and −15 and
+7 % for MEGAN, and affects the global emissions of monoterpenes by −43
and +40 % for ORCHIDEE and −11 and +3 % for MEGAN. Performing a
further sensitivity test, forcing ORCHIDEE with the MODIS LAI, confirms the
high sensitivity of the ORCHIDEE emission module to LAI variation. We find
that MEGAN is more sensitive to variation in the LDF parameter than ORCHIDEE.
Our results highlight the importance and the need to further explore the BVOC
emission estimate variability and the potential for using models to
investigate the estimated uncertainties. |
|---|---|
| ISSN: | 1680-7316 1680-7324 |