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Fig. 14.6
in
(
14.5
) for each 4D-Var cycle of the preliminary WCRA13 analysis sequence. Also shown are the
values of
Time series of the initial (
blue
)andfinal(
red
) values of the cost function log
10
.J/
J
NL
from (
14.2
) computed at the end of the single outer-loop (
red pluses
)
therefore only able to show some preliminary results from a sequence of benchmark
integrations for WCRA13 which were performed to assess storage requirements,
execution time, efficacy of the assimilation set-up, etc. The final analyses for
WCRA31 and WCRA13 are now available to the community via a dedicated
Opendap web server at
http://oceanmodeling.pmc.ucsc.edu
.
To illustrate the performance of 4D-Var in ROMS CCS, Fig.
14.6
shows a time
series of the initial and final values of the cost function
from (
14.5
) for each
data assimilation cycle of the preliminary WCRA13 sequence. In general, the cost
function is reduced by
50
J
-
70
% during most cycles. Also shown in Fig.
14.6
is the
value of
during most cycles. Clearly the
4D-Var procedure moves the model circulation estimates closer to the observations.
J
NL
from (
14.2
) which is consistent with
J
14.5
The CCS Near Real-Time Analysis and Forecast System
In addition to the historical analyses described in Sect.
14.4
, ROMS CCS is also
being used in conjunction with 4D-Var to compute analyses for the ocean in near
real-time. The system described here builds on previous experience using ROMS
4D-Var in real-time analysis and ensemble prediction mode in the Caribbean Sea
and the Gulf of Mexico by
Powell et al.
(
2009
). The near real-time aspect of this
system places strict constraints on the
prior
information and observations that can
be used in the assimilation system. The
prior
surface forcing fields are computed by
ROMS based on standard height atmospheric variables, surface radiation fluxes and
precipitation from COAMPS that is run at NRL Monterey in a near real-time mode.
There is no near real-time product available for constraining the model at the open
boundaries, so climatological open boundary conditions derived from WOA05 are
used as the prior in this case.
The CCS near real-time analysis system is run every Monday morning using
all of the available ocean observations from the previous week. The primal 4D-Var
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