Documentation of the Changes in INT2LM 1.8

Version 1.8 of the interpolation program INT2LM is available since end of May 2008. In the last months, the climate mode has been tested more intensively now by colleagues from the CLM community, and we incorporated more changes and bug fixes for that mode. At DWD we worked on the vectorization of the code, to prepare it for our new machines. The optimizations for the vector processors also speeded up the code on the IBM (and surely also on other scalar machines), which is mainly due to the fact, that we could save many computations in the vertical interpolations. Besides other technical adaptations and few bug fixes, we also introduced three new features. All changes are described in more detail below.

Contents:

1. Modifications since Version 1.7
• New Features
• Adaptations for the Climate Mode
• Technical Adaptations and Bug Fixes
• Optimizations for Vectorization
2. Changes in the Namelists
3. Changes of the Results

1. Modifications since Version 1.7

New Features

• Treatment of qr, qs, qg:
  There are developments going on to introduce prognostic variables for rain and snow into the global model GME of DWD. The INT2LM has been extended, to interpolate also these variables from the GME. Up to now, qr and qs could only be interpolated from the COSMO-Model itself. This feature is switched on by lprog_qrqs=.TRUE. and lgme2lm=.TRUE..
• External parameters for the subgrid scale orography (sso) scheme:
  Additional external parameters are read, if the subgrid scale orography scheme should be used for the coarser applications of the COSMO-Model. The reading of the additional parameters can be controlled by the new Namelist variable (in group /CONTRL/) lsso:

  Name	Meaning	Default
  lsso	to process parameters for sso scheme	.FALSE.

  The program for the external parameters has to be extended, to provide the necessary additional parameters. This work is still in progress.

• External parameters for the topographical corrections in the radiation scheme:
  Additional external parameters are read, if the corrections in the radiation scheme should be computed in the COSMO-Model. The reading of the additional parameters can be controlled by the new Namelist variable (in group /CONTRL/) lradtopo:

  Name	Meaning	Default
  lradtopo	to process parameters for topographic corrections of radiation	.FALSE.

  The program for the external parameters has to be extended, to provide the necessary additional parameters. This work is still in progress.

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Adaptations for the Climate Mode

For the climate mode, the following adaptations have been done:

• Alternative calls to the bicubic spline interpolation have been implemented in src_coarse_interpol.f90.
• Treatment of itype_rootdp:
  For the options 1 and 2, a bug was fixed. A new field to save the external field read from the parameter data set has been introduced. Another option (3) has been added.
• Treatment of itype_w_so_rel:
  The default of itype_w_so_rel has been set to 1
• Treatment of (NetCDF) undefined values for output:
  Some adaptations were necessary, if NetCDF files with undefined values are read, but GRIB output is done.
• Computation of control level for geopotential:
  Some climate models do not provide the geopotential on higher levels, therefore an option was added to compute this control level geopotential from the other input parameters.
• Interpolation from coarse grid models with lower upper boundary in the atmosphere:
  If input is taken from models, that have an upper boundary, which is lower than the desired upper boundary in the COSMO-Model, the vertical profile of every grid point of the coarse grid model is extended to the COSMO upper boundary.

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Technical Adaptations and Bug Fixes

• The name and meaning of the namelist variable lyear_360 has been changed to an integer value: itype_calendar, to allow several types of calendars:
  0: proleptic-gregorian calendar (default)
  1: a year with 360 days every year
• All variable names gz0 have been renamed to z0 and the (Grib) factor and bias have been removed: INT2LM only works with the z0-values, so there is no need for extra scaling.
• The namelist switch ldebug has been (definitely) eliminated, so it has to be removed from all Namelist input and runscripts!
• The subroutine xd (in module gme_utilities.f90), which does the diamond boundary update for global GME fields has been adapted to avoid problems at the diamond boundaries, when working with bitmap files.
• The Namelist parameter lcm2lm was not distributed to other nodes.
• Call to subroutines org_read_coarse_grid and org_coarse_interpol also for lcm2lm.
• The field w_cl_lm was deallocated two times, which caused troubles on some compilers.
• Interpolation of SST is not required (any more).
• Do not deallocate fis_in, if fic_in could not be read.

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Optimizations for Vectorization

• src_vert_interpol.f90:
  
  • Subroutines adapt_pressure_1, adapt_pressure_2: The IF-clause in the computation of the virtual temperature prevented the vectorization of this loop. Therefore, the computation of the different statement-functions for GME and IFS has been modified.
  • Subroutine adapt_pressure_2: In the Newton iterations, the IF (kcontrol_fi /= 1) prevented vectorization. The control geopotential is now computed before in a new variable.
  • Subroutine vert_interpol: The k-loop within the i-j-loops was moved outside The Spline interpolation has been modified, in order not to begin always from the very start. This saves a lot of computation time also on scalar systems.
• src_lm_fields.f90, src_vert_inter_lm.f90:
  Changes in the vertical interpolation analogous to src_vert_interpol.f90.
• gme_utilities.f90, src_gme_interpol.f90:
  The (many) IF-clauses for the Match-Interpolation prevented the vectorization of the routine pp_interp2ls. We introduced an initialization-routine for this interpolation, where weighting variables are computed only once. According to this change, Subroutine pp_interp2ls has been re-written.
• utilities.f90:
  Subrouinte horizontal_filtering: changed the i-loop and the loop over the filter weights, to vectorize over the i-loop.

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2. Changes of the Namelists

• Two variables have been eliminated: ldebug and lyear_360. Instead of ldebug, the variable idbg_level has to be used now. lyear_360 is replaced by the new variable itype_calendar.
• There are three new variables:
  

  Name	Meaning	Default
  lsso	to process parameters for sso scheme	.FALSE.
  lradtopo	to process parameters for topographic corrections of radiation	.FALSE.
  itype_calendar	for specifying the calendar used 0: gregorian calendar (default) (but this needs a bug fix in get_utc_date, because up to now we only have julian calendar) 1: every year has 360 days	0

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3. Changes of the Results

There are no changes to the results of the NWP applications.