2.2.2.1. Initialization of surface fields integrated in MESONH programs

In MESONH, there are usually 2 ways to produce initial files, depending if you want to use real or ideal atmospheric conditions. However, from the surface point of view, there is no difference between these 2 main possibilities of fields (real -e.g. from operationnal surface scheme in an operationnal model- or ideal -e.g. uniform-), whatever the treatment done for the atmospheric fields. This is allowed because the same externalized routines corresponding to PGD and PREP are used:

In the case of realistic atmospheric fields, the MESONH programs calling the surface are:

  1. PREP_PGD : it uses the PGD facility of the surface
  2. PREP_NEST_PGD : surface fields are only read and rewritten, except the orography that is modified (the modification of the orography itself is considered as an atmospheric model routine, as orography is also a field of the atmospheric model).
  3. PREP_REAL_CASE : it uses the PREP facility of the surface, that can produce either ideal or realistic surface fields.
  4. SPAWNING : it does not produce surface fields any more. The surface fields will be recreated during the PREP_REAL_CASE step following the SPAWNING.
    In the case of ideal atmospheric fields, the MESONH program calling the surface is PREP_IDEAL_CASE : it uses both the PGD and PREP facilities of the surface. Ideal or realistic (the latter only in conformal projection) physiographic fields can be either produced or read from a file. Then the prognostic surface variables, either ideal or realistic, can be computed by PREP.

If you use MESONH atmospheric model, the input and output surface files are the same as the atmospheric ones, so there is no need to specify via surface namelists any information about the input or output file names.

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