NAVDAS
Last Updated: Tuesday, 15-Jul-2008 11:04:59 PDT
NAVDAS GOES OPERATIONAL
1. Title: Operational Implementation of the NRL Atmospheric Variational
Data Assimilation System
2.Technical Point of Contact: 7531@nrlmry.navy.mil
/ 831-656-4739
3. Sponsor/Type Funding: 6.4 SPAWAR and
6.2 NRL Base
4. Abstract: The operational implementation
at Fleet Numerical Meteorology and Oceanography Center (FNMOC) of the
NRL Atmospheric Variational Data Assimilation System (NAVDAS) is the culmination
of an extensive research effort begun in 1996, led by the late Roger Daley.
NAVDAS is an observation-space-based three-dimensional variational data
assimilation suite for generating atmospheric state estimates to satisfy
a variety of Navy needs ranging from global initial conditions for Navy
global prediction to local initial conditions for forward-deployed mesoscale
prediction. Its implementation at FNMOC permits the Navy's atmospheric
forecast systems to benefit, for the first time, from the direct assimilation
of satellite radiances, which have resulted in significant forecast improvements
at other forecast centers.
5. Background: The development of NAVDAS
began in 1996, after visits were made to the National Centers for Environmental
Prediction (NCEP) and the Data Assimilation Office (DAO) at the NASA/Goddard
Space Flight Center to examine their data assimilation systems. The purpose
of NAVDAS development was to replace the multivariate optimum interpolation
(MVOI) data assimilation system, originally developed in the mid-1980's
and first implemented at FNMOC in 1988, with a competitive, state-of-the
art three-dimensional variational (3DVAR) data assimilation system. Unlike
the MVOI system, NAVDAS was designed to permit the direct assimilation
of satellite radiances into the Navy's data assimilation systems, a capability
that has resulted in significant forecast improvements at other forecast
centers and will be a necessary ingredient for all future data assimilation
systems. The formulation of NAVDAS in observation-space makes it possible
for the same software to be used to satisfy Navy needs ranging from providing
initial conditions for central site applications like the Navy Operational
Global Atmospheric Prediction System (NOGAPS) and the Coupled Ocean/Atmosphere
Mesoscale Prediction System (COAMPS™) as well as forward-deployed
applications like COAMPS-OS™ (On Scene). NAVDAS can perform central
site global assimilation on massively parallel super computers as well
as local data assimilation on workstations or personal computers with
the same code. Finally, NAVDAS was designed so that the nested analyses
required for COAMPS and COAMPS-OS™ can be produced simultaneously,
producing a seamless transition between the nests, and correcting a deficiency
in the MVOI system.
6. Accomplishment: Upon completion of its
development, NAVDAS was tested extensively under conditions designed to
closely mimic the operational environment at FNMOC. NAVDAS was found to
meet or exceed the performance of the current operational MVOI system
for all measures of skill required by FNMOC and was transitioned to FNMOC
in August 2003. NAVDAS was tested in real-time parallel operations at
FNMOC for over a year. Its performance in parallel operations confirmed
the results of our testing. NAVDAS passed its Optest in September 2003
by satisfying the following seven test criteria: (1) a scorecard of statistical
metrics, (2) synoptic performance, (3) tropical cyclone track performance,
(4) observational data quality control, (5) wave model performance, (6)
stress testing with limited data availability, and (7) classified data
assimilation functionality. NAVDAS has been proven to run robustly in
the FNMOC operational environment and has met all the requirements established
by the FNMOC Optest Panel for implementation into operations. On 1 October
2003, NAVDAS was operationally implemented at FNMOC as the data assimilation
system for NOGAPS.
7. Significance: With the operational implementation
of NAVDAS at FNMOC, the Navy will once again have a data assimilation
system that will permit the forecasts from its global and mesoscale atmospheric
prediction models to remain competitive with those produced by other forecast
centers around the world. The capability of NAVDAS to directly assimilate
satellite radiances will permit the Navy to benefit from the myriad of
advanced satellite sensor systems scheduled for operations over the next
decade. Furthermore, NAVDAS provides the Navy with a stepping stone to
more advanced data assimilation approaches (e. g., 4DVAR, Kalman Filter,
etc.) for the future.
8. Application: At FNMOC, NAVDAS will replace
all of the analysis, analysis error estimation, and quality control software
associated with the MVOI data assimilation system for NOGAPS and COAMPS™.
It will also be used to replace the MVOI data assimilation software for
COAMPS-OS™ at sites around the world.
9. References:
Validation
Test Report for the NAVDAS/NOGAPS Data Assimilation System (Report
hosted by FNMOC)
