Geoscience Reference
In-Depth Information
represent every 10th grid point. The vertical grid is comprised of 47 levels,
with the top 20 levels at a resolution of 10 m. Each three-dimensional vari-
able has dimension 1191
47 and a single snapshot is approximately
250 M bytes. A single snapshot of the five prognostic variables of the model
is 1.2 Gbytes.
The performance of the OFAM on the NEC SX6 has been measured dur-
ing two ocean model only integrations (so called “spinup”) using ERA40.
10
The first integration was performed using MOM4p0b, which included
the leap-frog time integration scheme and neutral physics using a baro-
clinic timestep of 300 s. This was performed on 21 processors across three
nodes sustaining 20.3 Gflops. The second integration was performed using
MOM4p0d, which included a new time integration scheme without neu-
tral physics using a baroclinic timestep of 600 s. This was performed on
42 processors across six nodes sustaining 31.8 Gflops demonstrating some
problems in scalability of the MOM software. The usage values are sum-
marised in Table 2. OFAM's I/O requirements are outlined in Table 3 and
include a complete ocean state specification either as initial conditions or
a restart, O(5) Gbytes.
×
968
×
3.2.
Data assimilation
BODAS
8
isanewsoftwarepackagedevelopedtoperformamulti-variate
analysis based on statistics derived from the global ocean forecast system.
The key feature of BODAS is the way it defines the background error
covariances which is based on the stationary covariance of an ensemble
Table 2.
Performance of OFAM (MOM4) on the NEC SX6.
Spinup I
Spinup II
Nodes
3
6
Cpu's (total)
21
42
Memory (total)
∼
86 GBytes
∼
114 GBytes
Cputime/model day
20 min
11.5 min
Sustained flops
20.3 Gflops
31.8 Gflops
Table 3. Input files required for the Ocean
Forecast Australia Model.
Input files
Size
Grid specification
∼
400 MBytes
Restart
∼
5GBytes
NWP surface fluxes
∼
150 MBytes
SST analysis
23 MBytes
