We will endeavour to keep track of all remaining issues (i.e. that have not been fixed on the PCMDI server) that have been found with our simulations or with the IPCC AR4 archive and allow access to files that are unable to be placed on the PCMDI server due to space limitations. All such files can be found here. As on the PCMDI server, the directory structure is model_name/expt/run/field.nc and all files follow the PCMDI conventions for names/structure etc.

GISS-ER

Data issues:

• All rlus/rlds files were initially incorrectly saved. Values over the ocean have however been retrieved and are available by ftp for all experiments.
• rsdscs fields were calculated by sampling only clear sky boxes and cannot be compared to other models that calculated clear sky values for all boxes.
• As described in Hansen et al (2005; 2007a (in press); 2007b (in press)), stratospheric ozone depletion over the period 1979 to 1997 was originally underestimated by a factor of 5/9. Simulations with the corrected ozone changes are available: 20C3M and AMIP experiments.

Code issues

• There was a small error in the solar insolation calculation that effectively shifts the vernal equinox by a day from the intended Mar 21 hr 0. The seasonal cycle is thus off by a day but is only clearly noticeable in the insolation diagnostics (note that the models use a fixed 365 day calendar with no leap years). This affected all GISS-ER and GISS-EH/GISS-EH2 simulations.

GISS-EH/GISS-EH2

New simulations GISS-EH2:

• After the submission of GISS-EH data to PCMDI, an algorithmic change was made to the ocean model which significantly improved the simulations. We have rerun all the simulations that were made with GISS-EH with the new version of the model (denoted by GISS-EH2) and we strongly encourage users to use data from GISS-EH2 instead of GISS-EH.

  The specific improvement made was in the HYCOM ocean code. The density of cold sea water depends mainly on salinity and very little on temperature. Therefore diagnosing temperature from advected fields of density and salinity (the conserved variables in HYCOM) at high latitudes can lead to inaccuracies. A combination of factors related to annual mixed-layer entrainment/detrainment created biases that occasionally led to excessive ice formation in the model.

  This problem was fixed when salinity was replaced by 'spiciness' during advection. For more details, see:

  • Bleck R (2005) On the use of hybrid vertical coordinates in ocean circulation modeling. In: Chassignet E (ed) Proc. Summer School of Oceanography, Lalonde, France. Kluwer Acad. Press
  • Sun, S., and R. Bleck, 2006: Multi-century simulations With the coupled GISS-HYCOM climate model: Control experiments. Clim. Dyn. 26, 407-428. DOI 10.1007/s00382-005-0091-7

  Unfortunately, space considerations at PCMDI has prevented the data from being available there, and so we are providing it here instead. Results from the 20C3M, PIcntrl and 1% to 2×CO₂ experiments are currently available.

Other issues

• The corrected ozone changes during 1979 to 1997 mentioned above were used in the 20th century runs in GISS-EH2.
• The native grid used in GISS-EH and GISS-EH2 is identical. Since the grid lines are not everywhere parallel to latitude and longitude lines as required by the IPCC data, the grid needed to be converted during post-processing. In GISS-EH2, we ended up using an output grid that is close to the native grid so that the least amount of interpolation is needed in the remapping process to preserve the information on the native grid.
• Velocity fields in the ocean component (uo, vo) inadvertently neglected the barotropic contribution. Corrected versions are available.

GISS-AOM

No outstanding issues are known.

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Please notify us about any additional issues that you come across at:

Dr. Gavin Schmidt
NASA Goddard Institute for Space Studies
2880 Broadway, New York, NY 10025 USA
gschmidt@giss.nasa.gov