Don't zero out patch%fuel%frac_burnt() before we use it

[adrifoster]

Fixes #1301 by checking inside the TransLitterNewPatch for the type of disturbance instead of zero-ing outside of the subroutine.

Description:

Removed the lines in spawn_patches that zero-d the frac_burnt array too soon.
Added checks in TransLitterNewPatch to check for fire disturbance and a fire on the patch:
If no fire, new local variable frac_burnt set to 0.0, otherwise use patch%fuel%frac_burnt

Collaborators:

@glemieux

Expectation of Answer Changes:

Yes - should change answers because before we weren't burning any fuel

Checklist

Contributor

• The in-code documentation has been updated with descriptive comments
• The documentation has been assessed to determine if updates are necessary

Integrator

• FATES PASS/FAIL regression tests were run
• Evaluation of test results for answer changes was performed and results provided

Test Results:

CTSM (or) E3SM (specify which) test hash-tag: ctsm5.3.012

CTSM (or) E3SM (specify which) baseline hash-tag: ctsm5.3.012

FATES baseline hash-tag: sci.1.80.4_api.37.0.0

Test Output:

Running tests now

[glemieux]

I like moving the check into TransLitterNewPatch. That said, do we need to make sure that currentPatch%fuel%frac_burnt is set to zero at the end of spawn_patches or is that already handled elsewhere?

[adrifoster]

I like moving the check into TransLitterNewPatch. That said, do we need to make sure that currentPatch%fuel%frac_burnt is set to zero at the end of spawn_patches or is that already handled elsewhere?

I added it to the top of the fire_model subroutine, where we zero other fire-related things. I don't know if this is the right place for it or not...

[glemieux]

Regression testing on derecho underway.

[glemieux]

Regression testing agsinst fates-sci.1.80.5_api.37.0.0-tmp-241219.n01.ctsm5.3.016 is showing DIFFs in the following tests:

FAIL ERS_Ld397.f10_f10_mg37.I2000Clm50Fates.derecho_gnu.clm-FatesCold BASELINE fates-sci.1.80.5_api.37.0.0-tmp-241219.n01.ctsm5.3.016: DIFF
FAIL ERS_Ld30.f45_f45_mg37.I2000Clm50FatesCruRsGs.derecho_intel.clm-FatesColdNoComp BASELINE fates-sci.1.80.5_api.37.0.0-tmp-241219.n01.ctsm5.3.016: DIFF
FAIL ERS_Ld397.f45_f45_mg37.I2000Clm50Fates.derecho_intel.clm-FatesColdNoComp BASELINE fates-sci.1.80.5_api.37.0.0-tmp-241219.n01.ctsm5.3.016: DIFF
FAIL SMS_Lm6.f45_f45_mg37.I2000Clm50FatesCruRsGs.derecho_intel.clm-Fates BASELINE fates-sci.1.80.5_api.37.0.0-tmp-241219.n01.ctsm5.3.016: DIFF

Spot checking the DIFFs, I think these make sense; I'm seeing changes to fire related history. @adrifoster would you take a look when you have a chance to confirm please?

Results: /glade/u/home/glemieux/scratch/ctsm-tests/tests_pr1302

[adrifoster]

@glemieux thanks!

yep these look right to me, just to plot some differences:
here are the differences in fire_closs (the new version is higher because now we are actually burning dead fuel):

which does affect ROS and fire intensity:

the new version is lower because fuel is actually lower:

[glemieux]

Thanks @adrifoster!