GFS upgrade:

[JonathanBelles]

This is from EUSWX:

http://www.nws.noaa.gov/om/notification ... rade-2.txt

QUOTE:
EFFECTIVE TUESDAY MAY 1 2007...BEGINNING WITH THE 1200
COORDINATED UNIVERSAL TIME /UTC/ RUN...THE NATIONAL CENTERS FOR
ENVIRONMENTAL PREDICTION /NCEP/ WILL UPGRADE THE GLOBAL FORECAST
SYSTEM /GFS/ TO IMPROVE ITS ACCURACY AND PRODUCTS.

http://www.nco.ncep.noaa.gov/pmb/changes/

[cycloneye]

ANALYSIS CHANGES:

1. REPLACE SPECTRAL STATISTICAL INTERPOLATION /SSI/ ANALYSIS
SYSTEM WITH GRIDPOINT STATISTICAL INTERPOLATION /GSI/
ANALYSIS SYSTEM.

2. USE OF INCREASED OBSERVATIONS INCLUDING FULL RESOLUTION
ATMOSPHERIC INFRARED SOUNDER /AIRS/ DATA...CONSTELLATION
OBSERVING SYSTEM FOR METEOROLOGY...IONOSPHERE AND CLIMATE
/COSMIC/ GLOBAL POSITIONING SYSTEM RADIO OCCULTATION /GPSRO/
DATA.

MODEL CHANGES:

3. MODIFY SIGMA COORDINATE SYSTEM TO A HYBRID SIGMA-PRESSURE
COORDINATE SYSTEM.

4. UPDATED GFS RADIATION MODULE

PRODUCT CHANGES:

5. SURFACE FLUX FILES HAVE 30 NEW RECORDS MAINLY FOR
HYDROLOGICAL USE

6. CHANGE OUTPUT OF GLOBAL DIAGNOSTIC ASSIMILATION SYSTEM
/GDAS/ FROM 3-HOURLY TO HOURLY

7. MODEL TO NATIVE OUTPUT FILE WILL CHANGE FROM A SIGMA
SPECTRAL BINARY FILE TO A HYBRID SPECTRAL BINARY FILE



Maybe our resident pro mets can chim in here to help us with these technnical words that many dont understand about the upgrade of GFS starting on May 1rst.

[milankovitch]

3. MODIFY SIGMA COORDINATE SYSTEM TO A HYBRID SIGMA-PRESSURE
COORDINATE SYSTEM.


The rest are kind of self-explanatory but sigma coordinates are terrain following. So it's switching from a modified sigma to a sigma at low levels and pressure aloft coordinates system.