NOUS41 KWBC 301342



Technical Implementation Notice 12-41

National Weather Service Headquarters Washington DC

942 AM EDT Thu Aug 30 2012


To:        Subscribers:

           -Family of Services

           -NOAA Weather Wire Service

           -Emergency Managers Weather Information Network


           Other NWS Partners, Users and Employees


From:      Tim McClung

           Chief, Science Plans Branch

           Office of Science and Technology


Subject:   New NGAC Aerosol Forecast System

           Effective September 11, 2012


Effective on or about Tuesday, September 11, 2012, the National Centers for Environmental Prediction (NCEP) will begin to run and disseminate data from the NOAA Environmental Modeling System Global Forecast System (GFS) Aerosol Component (NGAC).


NGAC is NCEP’s global in-line atmospheric-aerosol module within GFS. The aerosol component of the NGAC is the Goddard Chemistry Aerosol Radiation and Transport Model (GOCART).  Funded mainly by NASA’s Earth Science programs, the GOCART model was developed to simulate common atmospheric aerosols (sulfate, black carbon (BC), organic carbon (OC), dust, and sea-salt), CO, and sulfur gases. 


NGAC Version 1 provides 5-day forecasts of aerosol dust proxies and five dust particle size ranges listed below, once per day for the 0000 UTC cycle. The NGAC output will be available in GRIB2 format on a 1x1 degree output grid, with output available for 00 to 120 hours, with output every
3 hours.  The NGAC output will be disseminated via NCEP's ftp/http server at the following location:


Output files and their contents include:

(1) ngac.t00z.a2df$HR, where HR=00, 03, ...,120:

2D products including

AER_OPT_DEP_at550: dust aerosol optical depth at 550nm (dimensionless)

CR_AER_SFC_MASS_CON: coarse mode surface mass concentration (kg/m3)

FN_AER_SFC_MASS_CON: fine mode surface mass concentration (kg/m3)

CR_AER_COL_MASS_DEN: coarse mode column mass density (kg/m2)

FN_AER_COL_MASS_DEN: fine mode column mass density kg/m2

DUST_EMISSION_FLUX: dust emission fluxes (kg/m2/sec)

DUST_SEDIMENTATION_FLUX: dust sedimentation fluxes (kg/m2/sec)

DUST_DRY_DEPOSITION_FLUX: dust dry deposition fluxes (kg/m2/sec)

DUST_WET_DEPOSITION_FLUX: dust wet deposition fluxes (kg/m2/sec)



(2) ngac.t00z.a3df$HR, where HR=00, 03, ..., 120:

3D products at model levels including

PRES: pressure (Pa)

RH: relative humidity (%)

TEMP: temperature (K)

DUST1: dust bin1 (0.1-1 micron) mixing ratio (kg/kg)

DUST2: dust bin2 (1-1.8 micron) mixing ratio (kg/kg)

DUST3: dust bin3 (1.8-3 micron) mixing ratio (kg/kg)

DUST4: dust bin4 (3-6 micron) mixing ratio (kg/kg)

DUST5: dust bin5 (6-10 micron) mixing ratio (kg/kg)



(3) ngac.t00z.aod_$NM, where NM=11p1um, 1p63um, 340nm, 440nm, 550nm, 660nm, 860nm:

Aerosol optical depth at specified wavelengths (11.1, 1.63, 0.34, 0.44, 0.55, 0.66, and 0.86 micron)


A consistent parallel feed of data is currently available on the NCEP server via the following URL's:



Users please note that NGAC products are encoded in GRIB2 using a relatively-new GRIB template.  Users should download the latest versions of wgrib2 and the other NCEP GRIB utilities to use the NGAC output products.  Many of these utilities were updated on July 17, 2012.  Users can access the NCEP GRIB utilities from this URL:


A Website containing more information about NCEP's dust product can be found at:



For questions regarding the scientific content of the NGAC model please contact:


Sarah Lu


College Park, Maryland 20740



For questions regarding the dataflow aspects of these data

sets please contact:


Rebecca Cosgrove

NCEP/NCO Dataflow Team

College Park , Maryland 20740




NWS National Technical Implementation Notices are online at: