NCEP’s UNIFIED POST PROCESSOR (UPP)

Hui-Ya Chuang

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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.

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Components of the UPP

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GFS outputpost

copygb

The UPP has two components: post and copygb.

gfs_cntrl.parm

Visualization

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

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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

– 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 higher-

resolution model runs

• Membrane NCEP SLP:– Underground temperatures recomputed by relaxing

using successive overrelaxation.– Hydrostatic integration of this smooth underground

temperature field yields a much smoother SLP field.

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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

(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…

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GRIB packing precision**

Product description – post code keys on these character strings.

Each column represents a single model/isobaric level:

“1” = output, “0” = no output

• Users specify which fields or which level(s) of fields to output by modifying control file, e.g.,

** larger values more precision, but larger GRIB files.

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 01…) 2 5 7 10 20 30 50 70 75 100 125 150

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, 50, and 80 m AGL:

(U WIND AT FD HEIGHT) SCAL=( 4.0)L=(22200 00000 00000 00000 00000 00000 00000 00000 00000 00000…)

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For the flight/wind energy level fields:• “2” requests AGL. • “1” requests

above mean sea level.

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).

copygb.exe –xg”255 0 NX NY STARTLAT STARTLON 136

ENDLAT ENDLON DLAT DLON 64” in.grb out.grb

copygb –xg”255 0 401 401 10000 -130000 136 50000 -90000 100 100 64” in.grb out.grb

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map type (0=LTLN)

NE lat(millidegrees)

NE lon(millidegrees)

grid spacing(millidegrees)

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 GFS fields will be provided with tutorial

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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

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Questions???

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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 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 and derived radar reflectivity

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