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CESM CIME Case Control System configuration files
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Should high-res F-compset grid combos use tx12 mask? #52

Open zarzycki opened 2 years ago

zarzycki commented 2 years ago

Getting my feet wet with adding some new grids with nuopc. With a 15km MPAS grid + gx1v7 mask (a homebrew, admittedly, but templated using existing MPAS grids in CIME) I get the below 10m wind field for Hurricane Harvey that clearly shows a low resolution lnd/ocn mask.

  <model_grid alias="mpasa15natl_mpasa15natl" not_compset="_POP">
    <grid name="atm">mpasa15natl</grid>
    <grid name="lnd">mpasa15natl</grid>
    <grid name="ocnice">mpasa15natl</grid>
    <mask>gx1v7</mask>
  </model_grid>

gx1v7

You can see the "blockiness" associated with the land/sea mask and the corresponding fluxes provided to CAM (in this case, the land tiles are draggier than the ocean tiles, making for a sharp gradient in surface wind).

If I change the mask to tx0.1v2 in modelgrid_aliases_nuopc.xml...

  <model_grid alias="mpasa15natl_mpasa15natl" not_compset="_POP">
    <grid name="atm">mpasa15natl</grid>
    <grid name="lnd">mpasa15natl</grid>
    <grid name="ocnice">mpasa15natl</grid>
    <mask>tx0.1v2</mask>
  </model_grid>

tx01v2

I get a much better lnd/ocn mask more amenable to the high-resolution grid.

Perhaps a dumb question (feel free to close it if is!), but for all not_compset="_POP" combos that are of higher resolution than gx1v7, should we be using tx0.1v2 by default?

For example, all the MPAS grid configs (even the ones used for Earthworks, e.g., mpasa3p75_mpasa3p75_mg17?) are using the gx1v7 for masking by default, which would seem to have a similar issue as above.

adamrher commented 1 year ago

Perhaps a dumb question (feel free to close it if is!), but for all not_compset="_POP" combos that are of higher resolution than gx1v7, should we be using tx0.1v2 by default?

yes, hi-res F-cases should use the tx0.1v2 or tx0.1v3 ocean mask. Although I see many instances of using the gx1v7 mask w/ a hi-res atmos grid ... I presume it's just habit, but we should break this habit.