Documentation of the Changes in INT2LM
Version 2.06a / a_1

Contents:

0. Bug Fixes for Version 2.06a
1. Running COSMO-LEPS in GRIB 2
2. Additional packing for GRIB 2 fields
3. Modifications for MESSy
4. Technical Changes and Bug Fixes
5. Changes in the Namelists
6. Changes of the Results

0. Bug Fixes for Version 2.06a

These fixes have been implemented as version 2.06a_1 on 08.11.19.
A tar-file int2lm_191108_2.06a_1.tar is available on the server.

A problem occured with the local section 28, introduced for COSMO-LEPS. When no record of the input file has such a local section 28, the value lgot_loc28 is never set to .TRUE. and in the last cycle of the read-loop a deadlock could occur for the global communication, because not every MPI task then has a record to process.

In the module src_read_coarse_grid.f90 the checks for the local section 28 are now only done, if all records of a file do have local section 28 for COSMO-LEPS. Otherwise INT2LM stops with an error message.

The nunit_of_time is read from the input files and (up to this version) distributed by task 0 to all other tasks. But in rare cases it could happen, that task 0 does not get a valid nunit_of_time, while other tasks did.

The value for nunit_of_time is now taken from a global reduction over all tasks.

In the module io_utilities.f90, subroutine check_input_grid, a check has been added that the rotated pole is specified as the geographical north pole, in case a regular lat-lon grid is used as input grid.

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1. Running COSMO-LEPS in GRIB 2

(by D. Liermann)

To store the COSMO-LEPS GRIB 2 data in the ECMWF MARS archive, it is necessary to set some specific meta data in the local use section of GRIB 2. These meta data are defined in a special ECMWF local use section with localDefinitionNumber 28.

To enable INT2LM and the COSMO-Model to also write this special group of meta data with the same localInformationNumber 28 directly and without any further post-processing, this group of meta data is also included in the DWD definition files with localDefinitionNumber 28. With the linking mechanism for other centers this group will be available for other centers running INT2LM and the COSMO-Model.

• data_epsctl.f90:
  
  • Added variables for keys in local use section 28
• src_read_coarse_grid.f90:
  • Read necessary keys from IFS data.
  • Because not every MPI task necessarily reads a record with these information, the keys have to be distributed to all other MPI tasks.
  • Special treatment for localDefinitionNumber 28.
• src_lm_output.f90:
  • Set keys for localDefinitionNumber 28.

To read IFS data with ensemble information and write GRIB 2 data, the DWD definition set for eccodes is needed: definitions.edzw/grib2. This set contains modifications to include the definitions of local use section 28 (from ECMWF) and 250 (COSMO). With the linking mechanism, every center can create links to all necessary files within definitions.edzw/grib2 and can therefore use the same set of definitions as DWD.

IFS data are coded with localDefinitionNumber 30 (using keys number (of representative member RM), totalNumber, legBaseDate and legBaseTime) and with centre=98, subcentre=0. These data have to be modified with a (grib_filter) script to modify the local use section to localDefinitionNumber 28 (used for COSMO-LEPS files) and the necessary keys in this group. The localDefinitionNumber 28 also uses the key numberOfMembersInCluster, which is defined via a profile-script for the special cluster. Its value has to be taken from an environment variable set by this profile-script.

• in /CONTRL/: leps_ana=.TRUE.; leps_bc=.TRUE.
• in /DATA/: nlocaldefnr=28
• in /EPSCTL/: iepstyp_ana=203; iepstyp_bc=203

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2. Additional packing for GRIB 2 fields

(by Ulrich Schättler)

Up to now the packing type in INT2LM and the COSMO-Model was hard-coded as 'grid_simple'. But for GRIB 2 additional packing types have been introduced, which offer an additional packing and therefore result in smaller Grib files. The following packing types can now be used by INT2LM (2.06a) and COSMO (5.06b) by setting the new namelist variable: ypackingType (INT2LM: /DATA/; COSMO-Model: /GRIBOUT/)

• grid_ccsds:
  The Consultative Committee for Space Data Systems uses a Golomb-Rice packing scheme, which is rather efficient in terms of size and encoding size for transmitting gridded data. This algorithm can also be applied to meteorological data and is available in GRIB 2 now. Note that this is a lossless packing, but acts upon the grid_simple packing, which looses accuracy.
• grid_jpeg:
  JPEG 2000 Code Stream Format (Joint Photographic Experts Group) is also a lossless compression method, which acts upon grid_simple.
• grid_png:
  The png compression engine is based on the deflate method, which is a widely used, patent-free algorithm for universal, lossless data compression.

New Namelist Variable in /DATA/: ypackingType (Default: 'grid_simple')

NOTES:

1. To use these additional packing types, they also have to be activated for eccodes (with -DENABLE_JPG=ON, -DENABLE_PNG=ON, -DENABLE_AEC=ON). See also the installation instructions for eccodes.
2. The additional packing also takes additional computational time.

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3. Modifications for MESSy

(by Astrid Kerkweg, et al.)

The following modifications have been implemented by the MESSy Group:

• Preprocessor directives + code changes for compilation in MECO(n) system.
• Remove preproc version distinction for read/write routines.
• Remove obsolete change statement in src_read_hhl.f90.
• Additional bugfix in parameter list of read_gribapi.
• Change horizontal interpolation for ps for MESSYTWOWAY.
• Changes in vertical interpolation for 2-way coupling.
• Calculation of fic_in for 2-way coupling added (incl. one subroutine).
• Use consistent INTENT(IN) surface pressure in vert_interpol (valid for all applications, should not change results, as ps_lm is equal ps1_lm when the subroutine is called in standard-INT2LM.
• Use ps_lm in call of vert_interpol for u and v in ndef MESSYTWOWAY.
• Consistent treatment of humidity variables (w/o generalised humidity) For the 2-way coupling (and for the high-atmosphere configuration of COSMO) the humidity variables should not be treated together (the simple problem for the high atmosphere version is here, that the saturation parametrisation is not valid higher up in the atmosphere). Therefore we introduced the switch lgrh. Uli Blahak already implemented this, but we found further inconsistencies and cleaned up the code.

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4. Technical Changes and Bug Fixes

• src_2d_fields.f90: (by Thorsten Reinhardt)
  Added a minimal threshold value for rho_snow_lm in case snow is present (w_snow_lm > 0)

  Problem:
  ICON provides a value of 0.0 for rho_snow, where no snow is present. Interpolating such points together with snow points, where rho_snow ≥ 50.0 can lead to small values of rho_snow, which can lead to a crash in the COSMO-Model.

• src_lm_output.f90: (by Ulrich Schättler)
  Corrected nunit_of_time for GRIB 2 input and GRIB 1 output: have to convert minutes to hours or 15 minutes to be able to process more than 255 minutes.

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5. Changes of the Namelists

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6. Changes of the Results

Setting a minimal threshold value for rho_snow_lm has the potential to modify the results.

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