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Apply land fraction as land mask for IMS snow depth preprocessing#2079

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jiaruidong2017 wants to merge 2 commits intodevelopfrom
feature/imsproc_landfrac
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Apply land fraction as land mask for IMS snow depth preprocessing#2079
jiaruidong2017 wants to merge 2 commits intodevelopfrom
feature/imsproc_landfrac

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@jiaruidong2017
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@jiaruidong2017 jiaruidong2017 commented Feb 26, 2026

Description

Summary of the code changes in this PR:

  1. Use land fraction as land mask for consistency with the rest of GFS system
  2. Remove IMS derived snow observations over land ice
  3. Add low bound to snow density

Issues

Resolves #2078

Automated CI tests to run in Global Workflow

  • atm_jjob
  • C96C48_ufs_hybatmDA
  • C96C48_hybatmsnowDA
  • C96_gcafs_cycled
  • C48mx500_3DVarAOWCDA
  • C48mx500_hybAOWCDA
  • C96C48_ufsgsi_hybatmDA
  • C48_ufsenkf_atmDA
  • C96C48_hybatmDA

Remove derived IMS obs over landice
Add a low bound to snow density
std::max(80.0, std::min(120.0, tmp_density)) / 1000.0;
}
// where (density < 0.0001) density = 0.08
if (bkg_density(jnode, 0) < 0.0001) {
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is there any concern about something above 0.001 but below 0.08?

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This follows the implementation in original IMSproc repo as below:
https://github.com/NOAA-EMC/land-SCF_proc/blob/19957e5160f4793076d81549ffe88c17e1377583/sorc/IMSaggregate_mod.f90#L856

I agree that we can modify the logic so that if snow density is less than 0.08, it is reset to 0.08. After receiving confirmation from you and @ClaraDraper-NOAA, I will proceed with the changes.

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Use land fraction as land mask

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