Major bugs and issues in CLM5

The following summarizes major bugs and issues found since the release of CLM5

BUGS THAT HAVE NOT BEEN COMPLETELY FIXED ON MAIN NOR ON THE RELEASE BRANCH

• Issue#1332: Additional atm2lnd terms that have units of Pa need to be downscaled.

  There are a number of variables that have units of Pa and are derived through a multiplication by the gridcell-level pbot value. In columns where we downscale atmospheric quantities to the column level, pbot gets adjusted for each column. Some of these other variables are also downscaled, but not all. Potentially impacted quantities are co2, ch4 and variables that depend on pbot. This affects any configuration with CISM – where we downscale to vegetated columns as well as glacier columns over Greenland. It may also impact any configuration with multiple glacier elevation classes (which is typically the case over Greenland and Antarctica).

  This bug has not yet been fixed.

• Issue#675: Enabling carbon isotopes changes answers for transient cases

  13C and 14C soil C, litter C, root C, and soil respiration (below-ground quantities) are incorrect in simulations with land cover change. Above-ground quantities are ok.

  During land cover transition, 14C and 13C root carbon that should be transferred into 14C and 13C litter pools is mistakenly transferred to the bulk C litter pool. This has effectively no impact on bulk C or anything downstream in the coupled system. It affects 13C and 14C soil C, litter C, root C, and soil respiration where there has been land cover change. Note that all runs without land cover change are unaffected.

  The following variables published on ESG have been removed for all transient simulations (currently this is: amip, deforest-globe, historical, land-hist, land-hist-altStartYear, land-hist-cruNcep, land-hist-princeton, ssp126, ssp126-ssp370Lu, ssp370, ssp370-ssp126Lu, ssp585):

  c13Land, c13Litter, c13Soil, netAtmosLandC13Flux, rac13, rhc13, c14Land, c14Litter, c14Soil, netAtmosLandC14Flux, rac14, rhc14

  The following above-ground variables are ok and have not been removed from ESG:

  c13Veg, c14Veg, gppc13, and gppc14

  This bug has been fixed on main (ctsm1.0.dev036) and on the release branch (release-clm5.0.22), however, all current initial files generated from historical runs have incorrect C13/C14 pools/fluxes and so any simulation initialized from these files, even with the bug fix, will be incorrect.

  The following CMIP6 simulations are affected: CMIP6 Simulations

• Issue#592: Use of C13/C14 timeseries for non-transient control cases gives incorrect input when run long enough

  1850 or 2000 compsets non-transient simulations with CLM4.5/CLM5.0 and isotopes on will be using constant 1850 conditions until you run for more than 1850 years, when it will start running through the transient atm C13/C14 time-series instead of using constant 1850 conditions.

  No current spinups are affected.

  This bug has not yet been fixed.

  NO CMIP6 simulations are affected.

BUGS THAT HAVE BEEN COMPLETELY FIXED ON THE RELEASE BRANCH BUT NOT ON MAIN

BUGS THAT HAVE BEEN COMPLETELY FIXED ON MAIN BUT NOT ON THE RELEASE BRANCH

• Issue#953: Incorrect formula in LUNA

  LUNA has a term where the night-time and day-time effect is averaged. The formula as implemented uses the day-time value for both night and day.

  This bug has been fixed on main (ctsm1.0.dev102) but not on the release branch.

  ALL CMIP6 simulations are affected.

• Issue#958: LUNA day length factor

  The function, f(daylength), is a scaling factor that is based on the formulation in Bauerle et al. (2012). However, the denominator is set to 12, when it should be the maximum day length possible at a particular latitude (Bauerle et al., 2012). This may not be appropriate where some regions experience up to 24 hour day light in summer, which allows Equation 1 to be > 1, particularly around the summer solstice in June.

  This bug has been fixed on main (ctsm1.0.dev102) but not on the release branch.

  ALL CMIP6 simulations are affected.

• Issue#981: Luna Bug #3, hard coded initial conditions

  Along with #958 and #953, this seems to be a bug in the LUNA code where initial conditions at the start of the growing season for Vcmax and Jmax are hard coded to the same value, globally

  This bug has been fixed on main (ctsm1.0.dev102) but not on the release branch.

  ALL CMIP6 simulations are affected.

• Issue#803: Assumption that building width (Wb) equals street width can be relaxed and Wb can be derived from morphology

  There is an implicit assumption in the urban building energy model that building width equals street width. However, this assumption can/should be relaxed and building width can be derived from the morphology dataset. A simulation with the new equations indicate that as expected, for froof=0.5, answers are identical (because H/Ws = H/Wb). Differences in other cases depend on the degree of departure from froof=0.5 and the presence and magnitude of space heating and air conditioning. A full assessment of differences by variable, season, density type, and region can be found in the attached file in Issue#803.

  This bug has been fixed on main (ctsm1.0.dev102) but not on the release branch.

  ALL CMIP6 simulations are affected.

• Issue#785: Threshold for explicit snow pack initiation should use frac_sno_eff, not frac_sno

  This affects (a) runs with use_subgrid_fluxes = .false. (NOT the default); (b) urban points in all runs. The impact should be fairly small in both cases, since this just changes the timing of when an explicit snow pack is initiated, rather than using an unresolved (0-layer) snow pack. However, no formal simulations have been done to assess the impact on climate.

  This bug has been fixed on main (ctsm1.0.dev057) but not on the release branch.

  ALL CMIP6 simulations are affected (by (b) only as above).

• Issue#783: frac_sno is always 0 for lake points

  No formal simulations have been done to assess the impact on climate.

  This bug has been fixed on main (ctsm1.0.dev057) but not on the release branch.

  ALL CMIP6 simulations are affected.

• Issue#780: Possible bugs in CNFireLi2016Mod.F90

  A conversion of latitude from degrees to radians is not being done in the computation of "ig" (total ignitions). Diagnostics of the effects are available on the gitub issue page. Another possible bug was verified to be correct as is.

  This bug has been fixed on main (ctsm1.0.dev063) but not on the release branch.

  ALL CMIP6 simulations are affected.

• Issue#704: FUN code logic to reduce or increase carbon allocation used for uptake is reversed

  Carbon allocation to uptake responds to CN(uptake-cost) and CN(actual). The intended implementation is: For C:N less than the target C:N, C allocation is reduced with cost. For C:N greater than the target C:N, C allocation is increased with high C:N. However, the actual implementation is reversed.

  Our assessment is that the impact is relatively small, but would affect climate; however it doesn’t appear to strongly affect transient C response.

  This bug has been fixed on main (ctsm1.0.dev043) but not on the release branch.

  ALL CMIP6 simulations are affected.

BUGS THAT HAVE BEEN COMPLETELY FIXED ON MAIN AND THE RELEASE BRANCH

• Issue#1233: Ndep forcing incorrect when receiving ndep from CAM.

  This bug was introduced in ctsm5.1.dev002 and so does not affect the release branch.

  Any configurations that get ndep from coupler are affected (ndep_from_cpl true). This is only an issue in the mct cap.

  This bug has been fixed on main (ctsm5.1.dev019).

• Issue#1327: When using co2 from atmosphere with mct, it looks like values are taken just from the last gridcell on each proc

  This bug was introduced in ctsm5.1.dev002 and so does not affect the release branch. Only affects cases with co2_type='prognostic'.

  From an examination of the lnd_import routine in mct, it looks like, when co2 is received from atmosphere (prognostic), there is a bug that causes CTSM to use the co2 values from the last grid cell on a processor for all grid cells owned by that processor. The logic is also incorrect in the nuopc cap, in a different way.

  This bug has been fixed on main (ctsm5.1.dev032).

• Issue#545: Antarctica ice shelves are being treated as wetlands rather than glaciers

  This can impact science in scenario runs where the snowpack melts.

  This bug has been fixed on main (ctsm1.0.dev093) and the release branch (release-clm5.0.16).

  The following CMIP6 simulations are affected: CMIP6 Simulations

• Issue#624: QNOEVAP history output is incorrect.

  QNOEVAP output from publicly available simulations has been removed.

  This bug has been fixed on main (ctsm1.0.dev093) and the release branch (release-clm5.0.20).

  The following CMIP6 simulations are affected: CMIP6 Simulations

• PR#611: Reseed generic crops and increase totvegc threshold from 0 to 1

  A user reported odd (blocky) spatial patterns appear in generic crop leafc for BGC simulation when initialized from BGC-Crop (see [Issue#608] (https://github.com/ESCOMP/CTSM/issues/608)). To fix this, we now allow for reseeding of generic crops and increase the totvegc threshold that triggers this from 0 to 1 gC/m2. This is a work-around solution that addresses the isssue of dead generic crops in an accelerated-mode BGC simulation initialized from our current BGC-Crop initial files.

  This bug has been fixed on main (ctsm1.0.dev093) and the release branch (release-clm5.0.20).

  NO CMIP6 simulations are affected.

• Issue#538: In transient pft simulations with use_crop=.false., %crop does not advance from 1850 values

  Configurations affected: All transient pft configurations with create_crop_landunit = .true. and use_crop = .false. (which requires do_transient_crops = .false.)

  This bug has been fixed on main (ctsm1.0.dev013) and on the release branch (release-clm5.0.11).

  NO CMIP6 simulations are affected.

• Issue#590: Sporadic large CO2 uptake causing coupled CLM_CO2_TYPE=prognostic run to abort

  This is due to the fact that a large negative flux is coming from xsmrpool_to_atm_patch, which occurs at harvest in a single time step. This was fixed by dribbling the flux at crop harvest to the atmosphere over about a half year.

  This bug has been fixed on main (ctsm1.0.dev093) and on the release branch (release-clm5.0.16).

  NO CMIP6 simulations are affected.