 |
| Titel |
A semi-analytical solution to accelerate spin-up of a coupled carbon and nitrogen land model to steady state |
| VerfasserIn |
J. Y. Xia, Y. Q. Luo, Y.-P. Wang, E. S. Weng, O. Hararuk |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1991-959X
|
| Digitales Dokument |
URL |
| Erschienen |
In: Geoscientific Model Development ; 5, no. 5 ; Nr. 5, no. 5 (2012-10-11), S.1259-1271 |
| Datensatznummer |
250002852
|
| Publikation (Nr.) |
 copernicus.org/gmd-5-1259-2012.pdf |
|
|
|
|
|
| Zusammenfassung |
| The spin-up of land models to steady state of coupled carbon–nitrogen
processes is computationally so costly that it becomes a bottleneck issue
for global analysis. In this study, we introduced a semi-analytical solution
(SAS) for the spin-up issue. SAS is fundamentally based on the analytic
solution to a set of equations that describe carbon transfers within
ecosystems over time. SAS is implemented by three steps: (1) having an
initial spin-up with prior pool-size values until net primary productivity
(NPP) reaches stabilization, (2) calculating quasi-steady-state pool sizes
by letting fluxes of the equations equal zero, and (3) having a final
spin-up to meet the criterion of steady state. Step 2 is enabled by averaged
time-varying variables over one period of repeated driving forcings. SAS was
applied to both site-level and global scale spin-up of the Australian
Community Atmosphere Biosphere Land Exchange (CABLE) model. For the
carbon-cycle-only simulations, SAS saved 95.7% and 92.4% of
computational time for site-level and global spin-up, respectively, in
comparison with the traditional method (a long-term iterative simulation to
achieve the steady states of variables). For the carbon–nitrogen coupled
simulations, SAS reduced computational cost by 84.5% and 86.6% for
site-level and global spin-up, respectively. The estimated steady-state pool
sizes represent the ecosystem carbon storage capacity, which was 12.1 kg C m−2 with
the coupled carbon–nitrogen global model, 14.6% lower than
that with the carbon-only model. The nitrogen down-regulation in modeled
carbon storage is partly due to the 4.6% decrease in carbon influx (i.e.,
net primary productivity) and partly due to the 10.5% reduction in
residence times. This steady-state analysis accelerated by the SAS method
can facilitate comparative studies of structural differences in determining
the ecosystem carbon storage capacity among biogeochemical models. Overall,
the computational efficiency of SAS potentially permits many global analyses
that are impossible with the traditional spin-up methods, such as ensemble
analysis of land models against parameter variations. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|