An online ensemble coupled data assimilation capability for the Community Earth System Model: system design and evaluation
<p>The Community Earth System Model (CESM) developed by the National Center for Atmospheric Research (NCAR) has been used worldwide for climate studies. This study extends the efforts of CESM development to include an online (i.e., in-core) ensemble coupled data assimilation system (CESM-ECDA)...
| Main Authors: | , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2022-06-01
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| Series: | Geoscientific Model Development |
| Online Access: | https://gmd.copernicus.org/articles/15/4805/2022/gmd-15-4805-2022.pdf |
| Summary: | <p>The Community Earth System Model (CESM) developed by the
National Center for Atmospheric Research (NCAR) has been used worldwide for
climate studies. This study extends the efforts of CESM development to
include an online (i.e., in-core) ensemble coupled data assimilation system
(CESM-ECDA) to enhance CESM's capability for climate predictability studies
and prediction applications. The CESM-ECDA system consists of an online
atmospheric data assimilation (ADA) component implemented in both the
finite-volume and spectral-element dynamical cores and an online ocean
data assimilation (ODA) component. In ADA, surface pressures (<span class="inline-formula"><i>P</i><sub>s</sub></span>) are
assimilated, while in ODA, gridded sea surface temperature (SST) and ocean
temperature and salinity profiles at real Argo locations are assimilated.
The system has been evaluated within a perfect twin experiment framework,
showing significantly reduced errors of the model atmosphere and ocean
states through “observation” constraints by ADA and ODA. The weakly coupled data assimilation (CDA) in
which both the online ADA and ODA are conducted during the coupled model
integration shows smaller errors of air–sea fluxes than the single ADA and
ODA, facilitating the future utilization of cross-covariance between the
atmosphere and ocean at the air–sea interface. A 3-year CDA reanalysis
experiment is also implemented by assimilating <span class="inline-formula"><i>P</i><sub>s</sub></span>, SST and ocean
temperature and salinity profiles from the real world spanning the period
1978 to 1980 using 12 ensemble members. The success of the online CESM-ECDA
system is the first step to implementing a high-resolution long-term climate
reanalysis once the algorithm efficiency is much improved.</p> |
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| ISSN: | 1991-959X 1991-9603 |