 |
| Titel |
A new model of the global biogeochemical cycle of carbonyl sulfide – Part 2: Use of carbonyl sulfide to constrain gross primary productivity in current vegetation models |
| VerfasserIn |
T. Launois, P. Peylin, S. Belviso, B. Poulter |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 15, no. 16 ; Nr. 15, no. 16 (2015-08-20), S.9285-9312 |
| Datensatznummer |
250119981
|
| Publikation (Nr.) |
 copernicus.org/acp-15-9285-2015.pdf |
|
|
|
|
|
| Zusammenfassung |
Clear analogies between carbonyl sulfide (OCS) and carbon dioxide (CO2)
diffusion pathways through leaves have been revealed by experimental studies,
with plant uptake playing an important role for the atmospheric budget of
both species. Here we use atmospheric OCS to evaluate the gross primary
production (GPP) of three dynamic global vegetation models (Lund–Potsdam–Jena, LPJ; National
Center for Atmospheric Research – Community Land Model 4,
NCAR-CLM4; and Organising Carbon and Hydrology In Dynamic Ecosystems, ORCHIDEE). Vegetation uptake of OCS is modeled as a linear function of
GPP and leaf relative uptake (LRU), the ratio of OCS to CO2 deposition
velocities of plants. New parameterizations for the non-photosynthetic sinks
(oxic soils, atmospheric oxidation) and biogenic sources (oceans and anoxic
soils) of OCS are also provided. Despite new large oceanic emissions, global
OCS budgets created with each vegetation model show exceeding sinks by
several hundred Gg S yr−1. An inversion of the surface fluxes
(optimization of a global scalar which accounts for flux uncertainties) led
to balanced OCS global budgets, as atmospheric measurements suggest, mainly
by drastic reduction (up to −50 %) in soil and vegetation uptakes.
The amplitude of variations in atmospheric OCS mixing ratios is mainly
dictated by the vegetation sink over the Northern Hemisphere. This allows
for bias recognition in the GPP representations of the three selected
models. The main bias patterns are (i) the terrestrial GPP of ORCHIDEE at high
northern latitudes is currently overestimated, (ii) the seasonal variations
of the GPP are out of phase in the NCAR-CLM4 model, showing a maximum carbon
uptake too early in spring in the northernmost ecosystems, (iii) the overall
amplitude of the seasonal variations of GPP in NCAR-CLM4 is too small, and
(iv) for the LPJ model, the GPP is slightly out of phase for the northernmost
ecosystems and the respiration fluxes might be too large in summer in the
Northern Hemisphere. These results rely on the robustness of the OCS
modeling framework and, in particular, the choice of the LRU values (assumed
constant in time) and the parameterization of soil OCS uptake with small
seasonal variations. Refined optimization with regional-scale and seasonally
varying coefficients might help to test some of these hypothesis. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|