Eliashiv, J., A. C. Subramanian and A. J. Miller, 2020:
Tropical climate variability in the Community Earth
System Model: Data Assimilation Research Testbed
Climate Dynamics,
54, 793-806.
Abstract.
A new prototype coupled ocean-atmosphere Ensemble Kalman Fil8
ter reanalysis product, the Community Earth System Model using the Data
Assimilation Research Testbed (CESM-DART), is studied by comparing its
tropical climate variability to other reanalysis products, available observations
tions, and a free-running version of the model. The results reveal that
CESM-DART produces fields that are comparable in overall performance with those
of four other uncoupled and coupled reanalyses. The clearest signature of differences
in CESM-DART is in the analysis of the Madden-Julian Oscillation
(MJO) and other tropical atmospheric waves. MJO energy is enhanced over
the free-running CESM as well as compared to the other products, suggesting
the importance of the surface
ux coupling at the ocean-atmosphere interface
in organizing convective activity. In addition, high-frequency Kelvin waves in
CESM-DART are reduced in amplitude compared to the free-running CESM
run and the other products, again supportive of the oceanic coupling playing
a role in this difference. CESM-DART also exhibits a relatively low bias in the
mean tropical precipitation field and mean sensible heat
flux field. Conclusive
evidence of the importance of coupling on data assimilation performance
will require additional detailed direct comparisons with identically formulated,
uncoupled data assimilation runs.
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