NOUS41 KWBC 281909
PNSWSH
Technical Implementation Notice 12-17
National
Weather Service Headquarters Washington DC
310 PM EDT Wed Mar 28 2012
To:
Subscribers:
-Family of Services
-NOAA Weather Wire Service
-Emergency Managers Weather Information Network
-NOAAPORT
Other NWS Partners, Users and Employees
From:
Timothy McClung
Chief, Science Plans Branch
Office of Science and Technology
Subject:
Change to Wave Model Physics:
Effective Date May 8, 2012
Effective
on or about Tuesday, May 8, 2012, beginning with the 1200 Coordinated Universal
Time (UTC) run, the National Centers for Environmental Prediction (NCEP) will
introduce a physics upgrade and a few minor product changes to the Multi-grid
Global Wave Model.
This
model is currently run using WAVEWATCH-III v3.14.
The wave model will be upgraded to WAVEWATCH-III v4.5.1, which introduces
several new physics packages to the wave model. The key changes are as follows:
3. A
new physics package for wave dissipation due to wave breaking.
The
new physics packages are outlined in Ardhuin et. Al. 2010 (see full reference below). Validation studies show that the new physics significantly improve model skill
for wave height, especially in regions of strong swells such as the Pacific.
The
majority of the output products will remain unchanged. The number of stations
available in the point output products will be reduced by 112. The stations
that are being removed are - WALLOPS_?? (?? ranging from 01 to 61) and
SANCLEM_?? (?? ranging from 01 to 51). These stations were added in an
experimental mode and are now being removed. In addition, the spectral output
files will now be compressed due to their large sizes. The uncompressed files, including the multi_1.txxz.spec_tar
file (xx is the model cycle) will be removed from the NCEP server. Any
downstream users actively using these spectral output files will need to adapt
their software to use the compressed versions. Note that the tar files are
being compressed, the individual spectral files inside
the respective tarballs will not be compressed.
The
output data from these models are disseminated on the NCEP server at
http://www.ftp.ncep.noaa.gov/data/nccf/com/wave/prod/
and
ftp://ftp.ncep.noaa.gov/pub/data/nccf/com/wave/prod/
The
files that will be compressed are
akw.txxz.spec_tar becomes akw.txxz.spec_tar.gz
enp.txxz.spec_tar becomes enp.txxz.spec_tar.gz
wna.txxz.spec_tar becomes wna.txxz.spec_tar.ga
The
file multi_1.txxz.spec_tar will be removed. The file multi_1.txxz.spec_tar.gz has been available on the server for
some time.
Sample
output files from the new physics are available at
ftp://polar.ncep.noaa.gov/pub/waves/develop/
Details
about the NCEP Multi-grid Wave Model are online at:
http://polar.ncep.noaa.gov/waves/index2.shtml
These
changes will only correspond to the global wave model (multi_1). Upgrade of the
hurricane wave model (multi_2) will occur at a later date.
A
consistent parallel feed of data will be available on the NCEP server once the
model is running in parallel on the NCEP Central Computing System in late March.
The parallel data will be available via the following URLs:
http://www.ftp.ncep.noaa.gov/data/nccf/com/wave/para
ftp://ftp.ncep.noaa.gov/pub/data/nccf/com/wave/para
NCEP urges all users to ensure their
decoders can handle changes in content order, changes in the scaling factor
component within the product definition section (PDS) of the GRIB files,
changes to the GRIB Bit Map Section (BMS), and volume changes. These elements
may change with future NCEP model implementations. NCEP will make every attempt
to alert users to these changes before implementation.
For
questions regarding these model changes, please contact:
Hendrik Tolman
NCEP/Marine Modeling and Analysis Branch
Camp Springs, Maryland
301-763-8000 ext 7253
For
questions regarding the dataflow aspects of these data sets, please contact:
Rebecca Cosgrove
NCEP/NCO Dataflow Team
Camp Springs, Maryland 20746
301-763-8000 x 7198
ncep.list.pmb-dataflow@noaa.gov
Reference: Ardhuin, F. et.
al., 2010: Semi-empirical dissipation source functions for ocean waves: Part 1,
definition, calibration and validation. J.
Phys. Oceanogr., 40, 1917-1941.
NWS
National Technical Implementation Notices are online at:
http://www.nws.noaa.gov/os/notif.htm
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