NCEP’s UNIFIED POST
PROCESSOR (UPP)
Hui-Ya Chuang
1
Overview
• NCEP uses UPP as the common post processor
for all operational models.
• Forecasts from different models are computed
the same way in UPP and can therefore be
verified fairly.
• UPP generates output in GRIB1 or GRIB2.
2
Components of the UPP
The UPP has two components: post and
copygb.
post
Visualization
GFS output
copygb
gfs_cntrl.parm
3
Functions and features of post
• Performs vertical interpolation onto isobaric and
other non-model surfaces
• Computes diagnostic fields
• An MPI-parallel code
• Can be run as a post library on NEMS quilt server
4
Functions of copygb
• Performs horizontal interpolation to a
defined output grid
• Creates an output grid different than the
model integration domain.
• Performs de-staggering for models that
are on staggered grids
– NOTE: many visualization packages cannot
properly handle staggered grids
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Fields generated by the UPP
•
The UPP currently outputs hundreds of possible
fields.
–
Complete list in the Post Processing Utilities Chapter
of the user guide online:
http://www.dtcenter.org/wrf-nmm/users/docs/user_guide/V3/users_guide_nmm_chap1-7.pdf
•
Sample fields generated by UPP:
1) T, Z, humidity, wind, cloud water, cloud ice, rain,
snow, and aerosol on isobaric levels
2) Shelter level T, humidity, and wind fields
3) Two types of SLP
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Fields generated by the UPP
4) Precipitation-related fields: accumulated and
instantaneous precipitation for total, convective, and
grid scale
5) PBL-related fields: PBL height, 6 layers of PBL 30
hPa layer-averaged temperature, humidity, and wind
6) Radiative and Surface fluxes
7) Cloud related fields: Cloud fraction, Cloud
top/bottom p, Z, and T (conv, GS, total)
8) Aviation products: in-flight icing, turbulence and
ceiling
Fields generated by the UPP
9) Diagnostic fields:
Vorticity and geostrophic stream function
Isentropic fields
WMO-defined and dynamic tropopause fields
Precipitation type
Satellite look-alike products
Radar reflectivity for some models
Computation of atmospheric isobaric fields
•
Vertical interpolation of all state fields from
model to pressure levels is performed in linear
in ln(p) fashion.
•
The GFS model does not output height fields,
so the post processor generates model level
heights by integrating the hypsometric
equation.
Computation of underground isobaric fields
•
All underground wind components are the same as
those at the first model level above ground.
•
Temperature applies a constant qv computed from an
average of the 2nd and 3rd model levels above ground.
•
Humidity fields are defined by maintaining the average
RH of the 2nd and 3rd model levels above the surface.
Derivation of sea level pressure
• Standard NCEP SLP:
– Based on underground temperatures extrapolated using a
constant lapse rate, but subject to the Shuell correction.
– Can be very noisy over mountainous terrain in higherresolution model runs
• Membrane NCEP SLP:
– Underground temperatures recomputed by relaxing  2 T v  0 .
using successive overrelaxation.
– Hydrostatic integration of this smooth underground
temperature field yields a much smoother SLP field.
Computation of simulated Satellite
Products
• They are derived by calling Community Radiative
Transfer Model (CRTM) forward model using model
predicted cloud, moisture, and surface fields as input
• Allow users to make direct comparisons between
satellite observations and model forecast
• EMC has been generating NADIR simulated GOES
products operationally for both GFS and NAM since
2007
• HWRF has also been generating simulated GOES
operationally for several years and recently F-17 SSMIS
Computation of simulated radar
reflectivity
• Different algorithms are used depending on the
microphysics (MP) option used in the model run:
– Ferrier MP scheme: consistent with assumptions
made in Ferrier MP scheme (details in Ferrier’s 94
JAS publication).
– Other MP schemes: adopted from RIP4. More
information can be found online:
http://www.mmm.ucar.edu/wrf/users/docs/ripug.htm
– GFS currently does not output radar reflectivity
because its microphysics scheme does not have
suspended rain and snow.
Shelter level fields and PBL height
• Shelter level fields and PBL height are direct
output from each model
• They are not interpolated or diagnosed in the
post
• This ensures that these fields are derived within
the model based on surface and PBL physics
used in your model runs
Input to run post
• Post needs two input files:
1. itag: a text file which post reads via unit 5 to provide
information on
• model output file name
• format of model output (nemsio, binary, or netcdf)
• forecast validation time
• model name (GFS, NMM or NCAR)
2. gfs_cntrl.parm: control file specifying fields/levels
to output for Grib1
• In the scripts provided in with tutorial, these files
are automatically generated or linked
Post control file: gfs_cntrl.parm
• Users specify which fields or which level(s) of fields to
output by modifying control file, e.g.,
GRIB packing
precision**
(PRESS ON MDL SFCS ) SCAL=(6.0)
L=(11000 00000 00000 00000 00000 00000 00000…
(HEIGHT ON MDL SFCS ) SCAL=(6.0)
L=(11000 00000 00000 00000 00000 00000 00000…
Each column represents a single model/isobaric level:
“1” = output, “0” = no output
Product description – post
code keys on these
character strings.
** larger values  more
precision, but larger GRIB files.
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Post control file: gfs_cntrl.parm
• The included gfs_cntrl.parm file is used for
operational GFS post processing.
• The Table 3 in previously mentioned users’
guide explains the character string abbreviations
used in the control file:
http://www.dtcenter.org/wrf-nmm/users/docs/user_guide/V3/users_guide_nmm_chap1-7.pdf
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Outputting fields on different vertical
coordinates
• Post outputs on several vertical coordinates:
– Native model levels
– 47 default or user-specified isobaric levels
– 15 flight/wind energy levels: 30, 50, 80, 100, …, 2743,
3658, 4572, 6000 m (above ground or above MSL)
– 6 PBL layers: each averaged over a 30 hPa deep layer
– 2 AGL radar levels: 1000 & 4000 m
• Except for AGL radar and isobaric levels, vertical levels
are listed from the ground surface up in gfs_cntrl.parm.
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Examples of using Post control file
•
Output T every 50 hPa from 50 hPa to 1000 hPa:
(TEMP ON PRESS SFCS
) SCAL=( 4.0)
L=(00000 01001
2 5
7 10 20
30 50 70 75 100
01…)
125 150
Isobaric levels increase from left to right: 2, 5, 7, 10, 20, 30,
50, 70, then every 25 hPa from 75-1000 hPa.
Isobaric levels every 50 hPa:
L=(00000 01001 01010 10101 01010 10101 01010 10101 01010 10000 00000 00000 00000 00000)
Isobaric levels every 25 hPa:
L=(00000 01011 11111 11111 11111 11111 11111 11111 11111 10000 00000 00000 00000 00000)
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Examples of using Post control file
•
Output instantaneous surface sensible heat flux:
(INST SFC SENHEAT FX ) SCAL=( 4.0)
L=(10000 00000 00000 00000 00000 00000 00000 00000 00000 00000…)
•
Output the U-wind component at the 5 lowest model levels:
(U WIND ON MDL SFCS ) SCAL=( 4.0)
L=(11111 00000 00000 00000 00000 00000 00000 00000 00000 00000…)
For the flight/wind
•
Output U-wind component at 30, 50, and 80 m AGL:
energy level fields:
(U WIND AT FD HEIGHT) SCAL=( 4.0) • “2” requests AGL.
L=(22200 00000 00000 00000 00000 00000
00000above
00000 00000…)
• “1” 00000
requests
mean sea level.
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To run copygb
•
The generic command to run copygb and
horizontally interpolate onto a new grid is:
copygb.exe –xg”${grid}” in.grb out.grb
•
Two options on how to specify the target $grid:
1. Pre-defined NCEP standard grid number
2. User-defined grid definition
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Run copygb – Option 1
•
Interpolate to a pre-defined NCEP standard
grid (restrictive but simple)
– For example, to interpolate onto NCEP grid 212:
copygb.exe –xg212 in.grb out.grb
Descriptions of NCEP grids are available online:
http://www.nco.ncep.noaa.gov/pmb/docs/on388/tableb.html
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Run copygb – Option 2
•
Create a user-defined Latitude-Longitude grid by
specifying a full set of grid parameters
(complicated but flexible).
map type
(0=LTLN)
copygb.exe –xg”255 0 NX NY STARTLAT STARTLON 136
ENDLAT ENDLON DLAT DLON 64” in.grb out.grb
NE lat
NE lon
grid spacing
(millidegrees) (millidegrees) (millidegrees)
copygb –xg”255 0 401 401 10000
50000 -90000
100 100
-130000
136
64” in.grb out.grb
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GRIB file visualization with GrADS
• GrADS has utilities to read GRIB files on any nonstaggered grids and generate GrADS “control” files. The
utilities grib2ctl and gribmap are available via:
http://www.cpc.ncep.noaa.gov/products/wesley/grib2ctl.html
• Package download and user guide for GrADS are
available online:
http://grads.iges.org/grads/gadoc/
• A sample script to use GrADS to plot various GFS fields
will be provided with tutorial
24
Forecast plotted with GrADS:
Observed (L) and GFS derived (R) brightness
temperature for GOES water vapor channel
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Future plans
• Continue adding new products to the released
UPP code as they are developed, and expand
code portability
• Continue to improve efficiency of UPP
• Transition all operational model to output Grib2
26
Questions???
27
GRIB file visualization with GEMPAK
• The GEMPAK utility “nagrib” reads GRIB files from any
non-staggered grid and generates GEMPAK-binary files
that are readable by GEMPAK plotting programs
• GEMPAK can plot horizontal maps, vertical crosssections, meteograms, and sounding profiles.
• Package download and user guide are available online:
http://www.unidata.ucar.edu/content/software/gempak/index.html
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Forecast plotted with GEMPAK :
Precipitation and derived radar reflectivity
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