rdale
EF5
NOUS41 KWBC 071925 AAB
PNSWSH
TECHNICAL IMPLEMENTATION NOTICE XX-XX
NATIONAL WEATHER SERVICE HEADQUARTERS WASHINGTON DC
XXXX XM EST XXX XXX XX 2008
TO: FAMILY OF SERVICES /FOS/ SUBSCRIBERS...NOAA WEATHER
WIRE SERVICE /NWWS/SUBSCRIBERS...EMERGENCY MANAGERS
WEATHER INFORMATION NETWORK /EMWIN/ SUBSCRIBERS...
NOAAPORT SUBSCRIBERS...OTHER NATIONAL WEATHER SERVICE
/NWS/ PARTNERS AND USERS...NWS EMPLOYEES
FROM: PAUL HIRSCHBERG
SCIENCE PLANS BRANCH CHIEF
OFFICE OF SCIENCE AND TECHNOLOGY /OST/
SUBJECT: NORTH AMERICAN MESOSCALE MODEL CHANGES:
EFFECTIVE DECEMBER 02 2008
EFFECTIVE TUESDAY DECEMBER 2 2008...BEGINNING WITH THE 1200
COORDINATED UNIVERSAL TIME /UTC/ RUN...SEVERAL CHANGES WILL BE
MADE TO THE:
- WEATHER RESEARCH FORECAST NON-HYDROSTATIC MESOSCALE MODEL
/WRF-NMM/ RUNNING IN THE NORTH AMERICAN MESOSCALE MODEL /NAM/
- NAM DATA ASSIMILATION SYSTEM /NDAS/
- DOWNSCALED GLOBAL FORECAST SYSTEM /GFS/ WITH ETA EXTENSION
/DGEX/.
- GRIDPOINT STATISTICAL INTERPOLATION /GSI/ ANALYSIS WHICH
PROVIDES INITIAL CONDITIONS TO THE NDAS AND NAM FORECASTS.
THESE CHANGES ARE BEING MADE TO IMPROVE MODEL PERFORMANCE.
THE MODEL MODIFICATIONS INCLUDE:
1. A CHANGE TO THE WRF-NMM RADIATION PARAMETERIZATION...BY DOUBLING THE ABSORPTION COEFFICIENT FOR CLOUD WATER AND CLOUD ICE.
2. TWO COLD-SEASON RELATED CHANGES TO THE WRF-NMM LAND-SURFACE PHYSICS...CHANGING THE COMPUTATION OF POTENTIAL EVAPORATION TO DECREASE LINEARLY WITH BULK RICHARDSON NUMBER UNDER STABLE CONDITIONS /WEIGHTED BY SNOW COVERAGE/...AND ALLOWING THE SLOPE OF THE SATURATED HUMIDITY FUNCTION WITH RESPECT TO TEMPERATURE TO DECREASE LINEARLY WITH SNOW COVERAGE
3. CHANGING THE TURBULANT MIXING AND DIFFUSION SCHEMES SO THAT THEY VERTICALLY MIX AND DIFFUSE EACH HYDROMETEOR SPECIES SEPARATELY
THE ANALYSIS CHANGES INCLUDE:
1.ASSIMILATION OF NEW OBSERVATION TYPES...INCLUDING METOP2 RADIANCE DATA...AND TAMDAR/AMDAR AIRCRAFT DATA
2.USE OF THE LATEST (1Q 2008) VERSION OF THE GSI ANALYSIS...AND AN IMPROVED VERSION OF THE COMMUNITY RADIATIVE TRANSFER MODEL /CRTM/
THE CHANGES TO THE NDAS INCLUDE:
1.EACH NDAS CYCLE WILL BE INITIALIZED USING ATMOSPHERIC STATES FROM THE GLOBAL DATA ASSIMILATION SYSTEM /GDAS/ INSTEAD OF THAT FROM THE PREVIOUS NDAS CYCLE /SO-CALLED PARTIAL CYCLING OPTION/...NDAS LAND-SURFACE STATES WILL CONTINUE TO BE FULLY CYCLED FROM THE PREVIOUS NDAS RUN
2.THE OBSOLETE WRF STANDARD INITIALIZATION /WRF-SI/ SOFTWARE USED TO PROCESS THE GDAS FIRST GUESS FOR THE NDAS IS BEING REPLACED WITH THE NEW WRF PREPROCESSING SYSTEM /WPS/ SOFTWARE
3. REPLACE THE CURRENT AFWA SNOW DEPTH ANALYSIS WITH A NEW HIGHER RESOLUTION /23-KM/ AFWA ANALYSIS
ALL WRF-NMM MODEL CHANGES WILL BE SIMULTANEOUSLY IMPLEMENTED INTO THE DGEX...AS WILL THE REPLACEMENT OF WRF-SI SOFTWARE WITH WPS SOFTWARE...WHICH PROCESSES THE 78-H NAM FORECAST INTO INITIAL CONDITIONS TO THE DGEX
NAM OUTPUT CHANGES INCLUDE:
1.A NEW ENLARGED 32-KM OUTPUT GRID WHICH COVERS THE ENTIRE EXPANDED NAM COMPUTATIONAL DOMAIN...WHICH WILL HAVE THE SAME FIELDS AS THE EXISTING 32-KM GRID #221 /AWIP32/ FILE
2. ADD RICHARDSON NUMBER BASED PLANETARY BOUNDARY LAYER HEIGHT...MIXED LAYER DEPTH...AND TRANSPORT WIND COMPONENTS TO GRID #221 /AWIP32, 32 KM NORTH AMERICA/, GRID #218 /AWIP12, 12 KM CONUS/...AND GRID #242 /AWP242, 11.25 KM ALASKA/
STATIONS.
3.CHANGE THE NAM POST-PROCESSOR SOFTWARE TO USE SHELTER TEMPERATURE INSTEAD OF SKIN TEMPERATURE IN THE UNDERGROUND CHECK FOR LOWEST FREEZING LEVEL HEIGHT
4.ADD SNOW MIXING RATIO ON PRESSURE LEVELS TO THREE OUTPUT GRIDS /GRID #104..GRID #212...GRID #237/ THAT CURRENTLY ONLY OUTPUT CLOUD ICE...SO THAT TOTAL ICE CAN BE COMPUTED
THE COMBINED IMPACT OF THESE CHANGES HAS LED TO:
1. IMPROVED NAM FORECAST PERFORMANCE BASED ON QUANTITATIVE SKILL
SCORES FOR HEIGHTS AND TEMPERATURE /RMS ERROR AND BIAS/ OVER BOTH THE CONUS AND ALASKA
2. NEUTRAL OR BETTER QUANTATTIVE PRECIPITATION FORECAST SCORES /DEPENDING ON SEASON/ WITH LOWER PRECIPIATION BIAS
3. SLIGHT IMPROVEMENTS TO MOST NEAR-SURFACE FORECASTS... ESPECIALLY IN THE COLD SEASON /DUE TO THE WRF-NMM MODEL RADIATION CHANGE/
MORE DETAILS ABOUT THESE CHANGES CAN BE SEEN AT /USE LOWERCASE
LETTERS/:
http://www.emc.ncep.noaa.gov/MMB/MMBPLL/PARALOG/PARALOG.NAMY_PARTIALCYC.HTML
WHEN IT BECOMES AVAILABLE...A COPY OF THE BRIEFING PACKAGE FOR
THE NCEP DIRECTOR CAN BE FOUND AT /USE LOWERCASE LETTERS/:
http://www.emc.ncep.noaa.gov/MMB/NAMCHANGES_FALL2008/NAM_UPGRADES.FALL2008.HTML
DATA DELIVERY TIMING WILL NOT BE IMPACTED BY THIS IMPLEMENTATION. THE NAM DELIVERY TIME WILL NOT CHANGE.
DATA VOLUMES ARE EXPECTED TO CHANGE FOR SOME NAM OUTPUT GRIDS DUE TO THE CHANGES OUTLINED ABOVE. FOR THOSE GRIDS IMPACTED...THESE CONTENT CHANGES WILL IMPACT ALL DISSEMINATION
ROUTES WHICH INCLUDE NOAAPORT...THE NWS PUBLIC FTP SERVER AND THE NCEP PUBLIC FTP SERVER.
PARALLEL DATA FOR THE NAM...NDAS AND DGEX WILL BECOME AVAILABLE ON THE NCEP FTP SERVER ON OCTOBER 14 2008. IT WILL BE AVAILABLE AT THE LINKS BELOW /USE LOWERCASE LETTERS/:
ftp://ftp.ncep.noaa.gov/PUB/DATA/NCCF/COM/NAM/PARA
NCEP ENCOURAGES ALL USERS TO ENSURE THEIR DECODERS ARE FLEXIBLE
AND ARE ABLE TO ADEQUATELY HANDLE CHANGES IN CONTENT ORDER...
PARAMETER FIELDS CHANGING ORDER...CHANGES IN THE SCALING FACTOR
COMPONENT WITHIN THE PDS OF THE GRIB FILES AND ALSO ANY VOLUME
CHANGES WHICH MAY BE FORTHCOMING. THESE ELEMENTS MAY CHANGE WITH
FUTURE NCEP MODEL IMPLEMENTATIONS. NCEP WILL MAKE EVERY ATTEMPT
TO ALERT USERS TO THESE CHANGES BEFORE IMPLEMENTATION.
THIS AND OTHER NWS TECHNICAL IMPLEMENTATION NOTICES ARE AVAILABLE
ONLINE AT /USE LOWER CASE LETTERS/:
http://www.nws.noaa.gov/OM/NOTIF.HTM
$$
NNNN
PNSWSH
TECHNICAL IMPLEMENTATION NOTICE XX-XX
NATIONAL WEATHER SERVICE HEADQUARTERS WASHINGTON DC
XXXX XM EST XXX XXX XX 2008
TO: FAMILY OF SERVICES /FOS/ SUBSCRIBERS...NOAA WEATHER
WIRE SERVICE /NWWS/SUBSCRIBERS...EMERGENCY MANAGERS
WEATHER INFORMATION NETWORK /EMWIN/ SUBSCRIBERS...
NOAAPORT SUBSCRIBERS...OTHER NATIONAL WEATHER SERVICE
/NWS/ PARTNERS AND USERS...NWS EMPLOYEES
FROM: PAUL HIRSCHBERG
SCIENCE PLANS BRANCH CHIEF
OFFICE OF SCIENCE AND TECHNOLOGY /OST/
SUBJECT: NORTH AMERICAN MESOSCALE MODEL CHANGES:
EFFECTIVE DECEMBER 02 2008
EFFECTIVE TUESDAY DECEMBER 2 2008...BEGINNING WITH THE 1200
COORDINATED UNIVERSAL TIME /UTC/ RUN...SEVERAL CHANGES WILL BE
MADE TO THE:
- WEATHER RESEARCH FORECAST NON-HYDROSTATIC MESOSCALE MODEL
/WRF-NMM/ RUNNING IN THE NORTH AMERICAN MESOSCALE MODEL /NAM/
- NAM DATA ASSIMILATION SYSTEM /NDAS/
- DOWNSCALED GLOBAL FORECAST SYSTEM /GFS/ WITH ETA EXTENSION
/DGEX/.
- GRIDPOINT STATISTICAL INTERPOLATION /GSI/ ANALYSIS WHICH
PROVIDES INITIAL CONDITIONS TO THE NDAS AND NAM FORECASTS.
THESE CHANGES ARE BEING MADE TO IMPROVE MODEL PERFORMANCE.
THE MODEL MODIFICATIONS INCLUDE:
1. A CHANGE TO THE WRF-NMM RADIATION PARAMETERIZATION...BY DOUBLING THE ABSORPTION COEFFICIENT FOR CLOUD WATER AND CLOUD ICE.
2. TWO COLD-SEASON RELATED CHANGES TO THE WRF-NMM LAND-SURFACE PHYSICS...CHANGING THE COMPUTATION OF POTENTIAL EVAPORATION TO DECREASE LINEARLY WITH BULK RICHARDSON NUMBER UNDER STABLE CONDITIONS /WEIGHTED BY SNOW COVERAGE/...AND ALLOWING THE SLOPE OF THE SATURATED HUMIDITY FUNCTION WITH RESPECT TO TEMPERATURE TO DECREASE LINEARLY WITH SNOW COVERAGE
3. CHANGING THE TURBULANT MIXING AND DIFFUSION SCHEMES SO THAT THEY VERTICALLY MIX AND DIFFUSE EACH HYDROMETEOR SPECIES SEPARATELY
THE ANALYSIS CHANGES INCLUDE:
1.ASSIMILATION OF NEW OBSERVATION TYPES...INCLUDING METOP2 RADIANCE DATA...AND TAMDAR/AMDAR AIRCRAFT DATA
2.USE OF THE LATEST (1Q 2008) VERSION OF THE GSI ANALYSIS...AND AN IMPROVED VERSION OF THE COMMUNITY RADIATIVE TRANSFER MODEL /CRTM/
THE CHANGES TO THE NDAS INCLUDE:
1.EACH NDAS CYCLE WILL BE INITIALIZED USING ATMOSPHERIC STATES FROM THE GLOBAL DATA ASSIMILATION SYSTEM /GDAS/ INSTEAD OF THAT FROM THE PREVIOUS NDAS CYCLE /SO-CALLED PARTIAL CYCLING OPTION/...NDAS LAND-SURFACE STATES WILL CONTINUE TO BE FULLY CYCLED FROM THE PREVIOUS NDAS RUN
2.THE OBSOLETE WRF STANDARD INITIALIZATION /WRF-SI/ SOFTWARE USED TO PROCESS THE GDAS FIRST GUESS FOR THE NDAS IS BEING REPLACED WITH THE NEW WRF PREPROCESSING SYSTEM /WPS/ SOFTWARE
3. REPLACE THE CURRENT AFWA SNOW DEPTH ANALYSIS WITH A NEW HIGHER RESOLUTION /23-KM/ AFWA ANALYSIS
ALL WRF-NMM MODEL CHANGES WILL BE SIMULTANEOUSLY IMPLEMENTED INTO THE DGEX...AS WILL THE REPLACEMENT OF WRF-SI SOFTWARE WITH WPS SOFTWARE...WHICH PROCESSES THE 78-H NAM FORECAST INTO INITIAL CONDITIONS TO THE DGEX
NAM OUTPUT CHANGES INCLUDE:
1.A NEW ENLARGED 32-KM OUTPUT GRID WHICH COVERS THE ENTIRE EXPANDED NAM COMPUTATIONAL DOMAIN...WHICH WILL HAVE THE SAME FIELDS AS THE EXISTING 32-KM GRID #221 /AWIP32/ FILE
2. ADD RICHARDSON NUMBER BASED PLANETARY BOUNDARY LAYER HEIGHT...MIXED LAYER DEPTH...AND TRANSPORT WIND COMPONENTS TO GRID #221 /AWIP32, 32 KM NORTH AMERICA/, GRID #218 /AWIP12, 12 KM CONUS/...AND GRID #242 /AWP242, 11.25 KM ALASKA/
STATIONS.
3.CHANGE THE NAM POST-PROCESSOR SOFTWARE TO USE SHELTER TEMPERATURE INSTEAD OF SKIN TEMPERATURE IN THE UNDERGROUND CHECK FOR LOWEST FREEZING LEVEL HEIGHT
4.ADD SNOW MIXING RATIO ON PRESSURE LEVELS TO THREE OUTPUT GRIDS /GRID #104..GRID #212...GRID #237/ THAT CURRENTLY ONLY OUTPUT CLOUD ICE...SO THAT TOTAL ICE CAN BE COMPUTED
THE COMBINED IMPACT OF THESE CHANGES HAS LED TO:
1. IMPROVED NAM FORECAST PERFORMANCE BASED ON QUANTITATIVE SKILL
SCORES FOR HEIGHTS AND TEMPERATURE /RMS ERROR AND BIAS/ OVER BOTH THE CONUS AND ALASKA
2. NEUTRAL OR BETTER QUANTATTIVE PRECIPITATION FORECAST SCORES /DEPENDING ON SEASON/ WITH LOWER PRECIPIATION BIAS
3. SLIGHT IMPROVEMENTS TO MOST NEAR-SURFACE FORECASTS... ESPECIALLY IN THE COLD SEASON /DUE TO THE WRF-NMM MODEL RADIATION CHANGE/
MORE DETAILS ABOUT THESE CHANGES CAN BE SEEN AT /USE LOWERCASE
LETTERS/:
http://www.emc.ncep.noaa.gov/MMB/MMBPLL/PARALOG/PARALOG.NAMY_PARTIALCYC.HTML
WHEN IT BECOMES AVAILABLE...A COPY OF THE BRIEFING PACKAGE FOR
THE NCEP DIRECTOR CAN BE FOUND AT /USE LOWERCASE LETTERS/:
http://www.emc.ncep.noaa.gov/MMB/NAMCHANGES_FALL2008/NAM_UPGRADES.FALL2008.HTML
DATA DELIVERY TIMING WILL NOT BE IMPACTED BY THIS IMPLEMENTATION. THE NAM DELIVERY TIME WILL NOT CHANGE.
DATA VOLUMES ARE EXPECTED TO CHANGE FOR SOME NAM OUTPUT GRIDS DUE TO THE CHANGES OUTLINED ABOVE. FOR THOSE GRIDS IMPACTED...THESE CONTENT CHANGES WILL IMPACT ALL DISSEMINATION
ROUTES WHICH INCLUDE NOAAPORT...THE NWS PUBLIC FTP SERVER AND THE NCEP PUBLIC FTP SERVER.
PARALLEL DATA FOR THE NAM...NDAS AND DGEX WILL BECOME AVAILABLE ON THE NCEP FTP SERVER ON OCTOBER 14 2008. IT WILL BE AVAILABLE AT THE LINKS BELOW /USE LOWERCASE LETTERS/:
ftp://ftp.ncep.noaa.gov/PUB/DATA/NCCF/COM/NAM/PARA
NCEP ENCOURAGES ALL USERS TO ENSURE THEIR DECODERS ARE FLEXIBLE
AND ARE ABLE TO ADEQUATELY HANDLE CHANGES IN CONTENT ORDER...
PARAMETER FIELDS CHANGING ORDER...CHANGES IN THE SCALING FACTOR
COMPONENT WITHIN THE PDS OF THE GRIB FILES AND ALSO ANY VOLUME
CHANGES WHICH MAY BE FORTHCOMING. THESE ELEMENTS MAY CHANGE WITH
FUTURE NCEP MODEL IMPLEMENTATIONS. NCEP WILL MAKE EVERY ATTEMPT
TO ALERT USERS TO THESE CHANGES BEFORE IMPLEMENTATION.
THIS AND OTHER NWS TECHNICAL IMPLEMENTATION NOTICES ARE AVAILABLE
ONLINE AT /USE LOWER CASE LETTERS/:
http://www.nws.noaa.gov/OM/NOTIF.HTM
$$
NNNN
