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Presentation on theme: "NCEP’s UNIFIED POST PROCESSOR (UPP)"— Presentation transcript:

Hui-Ya Chuang

2 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.

3 Components of the UPP The UPP has two components: post and copygb.
GFS output Visualization copygb gfs_cntrl.parm

4 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

5 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

6 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: Sample fields generated by UPP: T, Z, humidity, wind, cloud water, cloud ice, rain, snow, and aerosol on isobaric levels Shelter level T, humidity, and wind fields Two types of SLP

7 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

8 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

9 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.

10 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.

11 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.

12 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

13 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: GFS currently does not output radar reflectivity because its microphysics scheme does not have suspended rain and snow.

14 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

15 Input to run post Post needs two input files:
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) 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

16 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=( … (HEIGHT ON MDL SFCS ) SCAL=(6.0) 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.

17 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:

18 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.

19 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=( …) Isobaric levels increase from left to right: 2, 5, 7, 10, 20, 30, 50, 70, then every 25 hPa from hPa. Isobaric levels every 50 hPa: L=( ) Isobaric levels every 25 hPa: L=( )

20 Examples of using Post control file
Output instantaneous surface sensible heat flux: (INST SFC SENHEAT FX ) SCAL=( 4.0) L=( …) Output the U-wind component at the 5 lowest model levels: (U WIND ON MDL SFCS ) SCAL=( 4.0) L=( …) Output U-wind component at 30, 50, and 80 m AGL: (U WIND AT FD HEIGHT) SCAL=( 4.0) L=( …) For the flight/wind energy level fields: “2” requests AGL. “1” requests above mean sea level.

21 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: Pre-defined NCEP standard grid number User-defined grid definition

22 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:

23 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” NX NY STARTLAT STARTLON ENDLAT ENDLON DLAT DLON 64” in.grb out.grb copygb –xg” ” in.grb out.grb map type (0=LTLN) Skim through just to show users how to project onto their own LL grid. NE lat (millidegrees) NE lon (millidegrees) grid spacing (millidegrees)

24 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: Package download and user guide for GrADS are available online: A sample script to use GrADS to plot various GFS fields will be provided with tutorial

25 Forecast plotted with GrADS: Observed (L) and GFS derived (R) brightness temperature for GOES water vapor channel

26 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

27 Questions???

28 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:

29 Forecast plotted with GEMPAK : Precipitation and derived radar reflectivity


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