[Ncep.list.emc.fv3gfs_tickets] FV3GFS Ticket #18: update to global_chgres and regrid_nemsio

[FV3GFS Trac Ticket]

#18: update to global_chgres and regrid_nemsio
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  Reporter:  philip.pegion@…  |      Owner:  Philip Pegion
      Type:  enhancement      |     Status:  new
  Priority:  major            |  Milestone:
 Component:  component1       |    Version:
Resolution:                   |   Keywords:
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Comment (by philip.pegion@…):

 Comment by S-J Lin:

 Hi all, in particular, Vijay:

 I think this change in surface pressure interpolation must be proven
 before it gets into the trunk (to be used by all). It must be evaluated
 and validated with hindcasts (many cases). We can not just rely on a
 single instance in a local area to make this change that will have
 significant impact for future research and operation.

 The physics and justification of using lapse rate of standard atmosphere
 does not stand once I thought about it more deeply. It is a horizontal
 interpolation. The use of the lapse rate, and under hydrostatic balance,
 is valid only for vertical interpolation. From grid point to grid point in
 the horizontal direction, there is NO hydrostatic balance relationship.
 Even for vertical interpolation, the assumption of a constant lapse rate
 is not universally correct.

 I firmly believe that code changes like this MUST be evaluated with, say
 74 cases of hindcasts (to cover a full year). We routinely do the 74-case
 hindcast whenever we made scientific change in the FV3. This is a quality
 control issue that we as a team must do, if we are to maintain a high
 level of forecast skill.

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Ticket URL: <https://svnemc.ncep.noaa.gov/trac/fv3gfs/ticket/18#comment:3>
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