- September 2019: A memory corruption bug has been discovered and corrected that arises when POP is setup with some block decompositions. The bug corrupts the physical solution. We do not have a quantification of the severity of the memory corruption, we just know that solutions are affected. The update also provides block decompositions for block counts that are multiples of 36, as is common on cheyenne. The new decompositions also avoid the memory corruption problem that is now fixed. This issue affects releases cesm1_1_2_LENS_n17, cesm1_1_2_LENS_n18, and cesm1_1_2_LENS_n19 when run on cheyenne. It is recommended that users no longer use releases n17-n19 (all built in mid-2019), and to use cesm1_1_2_LENS_n20 or newer. Note that this issue does not affect the 40-member LENS, the pre-industrial control, or any of the publicly released LENS experiments listed on the Simulations and Diagnostics page.
- August 2018: Daily PRECTMX (maximum precipitation over the day, filenames of form CASE.cam.h1.PRECTMX.[...]) data from all simulations are identical to PRECT (daily average precipitation) due to a model namelist input specification error. This issue cannot be corrected, and these data should not be used for assessing daily maximum precipitation. These data have been withdrawn from the Climate Data Gateway
- April 2018: It was discovered that 23 of the 33 daily sea ice fields (cice.h1) from 20C run b.e11.B20TRC5CNBDRD.f09_g16.035 have all values set to zero for a small set of days. The following fields are incorrect:
aice_d aicen003_d aicen004_d aicen005_d aisnap_d apond001_d apond005_d congel_d daidtd_d daidtt_d dvidtd_d dvidtt_d frazil_d fs_d FYarea_d hi_d hisnap_d hs_d meltb_d meltl_d melts_d rain_d snoice_d snow_d
for the following dates:
30-MAR-1969 31-MAR-1969 01-APR-1969.
No correction will be made, so use these data from this run with caution.
- September 2017: It was discovered that numerous monthly ocean variable timeseries incorrectly contained zeroes as values for member #33 (b.e11.B20TRC5CNBDRD.f09_g16.033) for April 1938 (only). It was determined that the best course of action is to set all ocean variables for member #33 for April 1938 to the appropriate missing value. The files on the HPSS and on the ESG have been updated with this fix. If you have previously downloaded monthly ocean data for member #33 for April 1938 it is suggested that you either set your data for that month to missing, or that you redownload the data from the HPSS or the ESG.
- September 2016: A small systematic difference between the CESM Large Ensemble runs done on the NCAR supercomputer Yellowstone without compression (members 1-30, 32, 34, 35) and CESM Large Ensemble runs done on the University of Toronto supercomputer (members 101-105) has been detected. Specifically, the global mean temperature in the University of Toronto runs (Figure 1, plotted in red) is systematically larger than the global mean temperature in the Yellowstone runs
(Figure 1, plotted in black). The origin of this systematic difference is a research
question. Differences in compiler interpretation or machine architecture may be
responsible. At present, there is no evidence linking this systematic difference to an
error in the implementation of the experimental protocol.
Plotting the first 50 days of the CESM Large Ensemble runs shows the expected
initial tight clustering of ensemble members and the expected increase in ensemble
spread associated with chaotic atmospheric circulation. Over the first 50 days, the
University of Toronto runs (Figure 2, plotted in red) are indistiguishable from
Yellowstone runs (Figure 2, plotted in black). CESM Large Ensemble users should
decide if this known systematic difference impacts their study. We are continuing to
examine the source of this difference as research resources allow. We will provide
any additional updates here.
Figure 1. Globally averaged annual-mean surface temperatures (TS) from the CESM Large Ensemble. Black lines represent members run on the Yellowstone supercomputer (members 1-30, 32, 34 and 35). Red lines represent members run on the University of Toronto supercomputer (members 101-105). Figure courtesy Vineel Yettella, University of Colorado.
Figure 2. Globally averaged daily mean surface temperature (TS). Black lines represent members run on Yellowstone supercomputer (members 1-30, 32, 34 and 35). Red lines represent members run on the University of Toronto supercomputer (members 101-105). Figure courtesy Vineel Yettella, University of Colorado.
- October 2015: There is a discontinuity in prescribed ozone concentration values between December 2080 and January 2081 in ensemble members 2-7 and 9-33. This is due to the fact that the CMIP5 ozone file was used starting in January 2081 instead of the WACCM ozone file. This error is expected to mainly affect the high-latitude Southern Hemisphere stratosphere and troposphere in austral spring and summer. Note: This known issue has no impact on any of the ensemble members before 2081. Note also that ensemble members 1, 8 and 34-40 use WACCM ozone throughout the entire period of simulation (1920-2100).
- October 2013: Ocean biogeochemistry was corrupted in ensemble members #3-8. This issue impacts all ocean biogeochemistry output fields, as well as some of the diagnostic atmospheric CO2 tracers; all other output for ensemble members #3-8 is unaffected. Affected history output has been removed in order to avoid corruption of analysis. While restart files for these ensemble member are available for use, users are advised against using them to initialize sensitivity experiments if their anticipated analysis includes ocean or atmosphere biogeochemistry fields. Note: This known issue has no impact on the physical climate system.