Transcript NCEP’s WRF POST PROCESSOR

NCEP’s UNIFIED POST
PROCESSOR (UPP)
Hui-Ya Chuang
NOAA/NCEP/EMC
2015 NMMB Tutorial
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Overview
• NCEP uses UPP as the common post processor for all
operational models, including NAM (NMMB), GFS,
GEFS, HWRF, SREF, RAP, and HRRR
• Forecasts from different models are computed the
same way in UPP and can therefore be verified fairly
• UPP generates output in GRIB1 or GRIB2
• UPP enables product generation on any output grid
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Components of the UPP
The UPP has two components: post and copygb.
post
Visualization
NMMB output
copygb
post control file
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Functions and features of post
• Performs vertical interpolation onto isobaric and
other non-model surfaces
• Computes diagnostic fields
• An MPI-parallel code that will run faster with more
processors
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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, such as NMMB
– 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 NMMB 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 (Shuell):
– Based on underground temperatures extrapolated using a
constant lapse rate, but subject to the Shuell correction.
– Can be very noisy over mountainous terrain in higher-resolution
model runs
• Membrane NCEP SLP:
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– Underground temperatures recomputed by relaxing
using
Tv  0.
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 NAM (NMMB) and GFS since 2007
• HWRF also outputs several simulated microwave products
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).
– Thompson MP scheme: computed in model
– Other MP schemes: adopted from RIP4. More
information can be found online:
http://www.mmm.ucar.edu/wrf/users/docs/ripug.htm
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 (e.g., NMM for NMMB)
2. nam_cntrl.parm: post 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: nam_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: nam_cntrl.parm
• The included nam_cntrl.parm file is used for
operational NAM 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 nam_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…)
•
Output U-wind component at 30,For
50, the
and 80
m AGL:
flight/wind
(U WIND AT FD HEIGHT) SCAL=( 4.0) energy level fields:
L=(22200 00000 00000 00000 00000 00000
00000AGL.
00000 00000…)
• “2” 00000
requests
• “1” requests above
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). Below is an example to project on a latlon grid
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
-130000
100 100
64” in.grb out.grb
136
50000 -90000
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GRIB file visualization with GrADS
• GrADS has utilities to read GRIB files on any non-staggered
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 NMMB fields will
be provided with tutorial
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Forecast plotted with GrADS:
Observed (L) and 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 .
GFS and RAP have transitioned to Grib2 in recent
upgrades. NAM and GEFS will soon in their upcoming
upgrades
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GRIB file visualization with GEMPAK
• The GEMPAK utility “nagrib” reads GRIB files from any nonstaggered grid and generates GEMPAK-binary files that are
readable by GEMPAK plotting programs
• GEMPAK can plot horizontal maps, vertical cross-sections,
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, Sea
Level Pressure, and 10 m wind
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Questions???
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