Back to Example List

Can one generate 3hr input data if only 6hr input data is available in the analysis files?

This is not a recommended option, but if one has a lot of good quality observations available at a very temporal high resolution, creating 3hr analysis data in REGRID may have an advantage.

Download a test dataset: ftp://ftp.ucar.edu/mesouser/MM5V3/TESTDATA/FNL_test_data.TAR.gz

Inside the test dataset listed above, you will find the following files:

   FNL/fnl_030311_00_00
   FNL/fnl_030311_06_00
   FNL/fnl_030311_12_00
   FNL/fnl_030311_18_00
   FNL/fnl_030312_00_00

All fields for each time period is stored in a separate file.

Below is an extract from the pregrid.csh file. Listed are the settings you need to change / pay attention to.

# Tell the script in which directory the data file is
set DataDir = /home/$USER/MM5V3/REGRID/pregrid/FNL

# These data files are in GRIB format
#set SRC3D = ON84       # Old ON84-formatted NCEP GDAS analyses
# set SRC3D = NCEP    # Newer GRIB-formatted NCEP GDAS analyses
set SRC3D = GRIB     # Many GRIB-format datasets

# Tell the script where the data files are, and that you called them (wild card permitted)
set InFiles = ( ${DataDir}/fnl* )

# The source of our SST is the same as for the 3D and surface data
set SRCSST = $SRC3D
# set SRCSST = ON84
# set SRCSST = NCEP
# set SRCSST = NAVY

# Since the SST data is also in these files, there is no need to repeat the details here
set InSST = ( )

# The source of our SNOW cover data is the same as for the 3D and surface data
set SRCSNOW = $SRC3D
# set SRCSNOW = ON84
# set SRCSNOW = GRIB

# Since the SNOW cover data is also in these files, there is no need to repeat the details here
set InSnow = ()

# We are not interested in SOIL data at this stage
# set SRCSOIL = $SRC3D

# We are not interested in SOIL data at this stage
# set InSoil = ()

#
# Remember to set the correct dates for your case
#
START_YEAR = 2003 # Year (Four digits)
START_MONTH = 03 # Month ( 01 - 12 )
START_DAY = 11 # Day ( 01 - 31 )
START_HOUR = 00 # Hour ( 00 - 23 )

END_YEAR = 2003 # Year (Four digits)
END_MONTH = 03 # Month ( 01 - 12 )
END_DAY = 12 # Day ( 01 - 31 )
END_HOUR = 00 # Hour ( 00 - 23 )

INTERVAL = 10800       << Setting this to 3hr, although only 6hr data is available will force interpolation to 3hr

# This is GRIB data so we need to supply the correct Vtables here - AVN and FNL data has the same grib codes, so we will use the AVN Vtables here as they have already been created
set VT3D = ( grib.misc/Vtable.AVN3D )
set VTSST = ( grib.misc/Vtable.AVNSST )
set VTSNOW = ( grib.misc/Vtable.AVNSNOW )
set VTSOIL = ( grib.misc/Vtable.xxxSOIL )            << We are not interested in SOIL data

This will create the following files:

To use these files in regridder set root in the regridder namelist.input to:

   root = '../pregrid/FILE' '../pregrid/SST_FILE' '../pregrid/SNOW_FILE'

Set the INTERVAL in regridder namelist.input to 10800 as well to take advantage of the 3hr analysis data.