Decadal Prediction Large Ensemble Simulation details

CESM Code base

The Decadal Prediction Large Ensemble (DPLE) used the same CESM code base, configuration details, component resolutions (nominally 1-degree in both atmosphere and ocean), and external forcing using the same CESM code base, configuration details, component files and resolutions (nominally 1-degree in both atmosphere and ocean) as were used in the CESM LENS project. Several of the LENS external forcing datasets were stitched together to provide continuous coverage across the modern to future (RCP85) transition. The DPLE therefore represents the "initialized" complement to the LENS simulations. The LENS tag was based on the CESM1.1 code base and was preserved in a special CESM tag: cesm1_1_2_LENS. All DPLE cases were generated from the B20TRLENS compset, and modified using namelist changes.

Initial Conditions

The DPLE comprises 62 distinct ensembles, one for each of 62 initialization times (November 1 of 1954, 1955, ..., 2014, 2015). For each start date, a 40-member ensemble was generated by randomly perturbing the atmospheric initial condition at the round-off level using a CAM namelist parameter. The simulations were integrated forward for 122 months after initialization. Observation-based ocean and sea ice initial conditions for the 1954-2015 period were obtained from a reanalysis-forced simulation of the CESM ocean and sea ice models. The initial conditions for the atmosphere and land models were obtained from LENS member 34 at corresponding historical times.

Setup instructions + component Namelist changes

DPLE Forcing

Present day and future (RCP8.5) atmospheric forcing files were joined to provide continuous coverage across the 2005-2006 year boundary. These concatenated files were sequenced from the original LENS forcing files, and are available on the NCAR glade filesystem (/glade/p/cesm/cseg/inputdata), and on NCAR's SVN input database [ https://svn-ccsm-inputdata.cgd.ucar.edu/trunk/inputdata/]

To gain access the NCAR files from the SVN repository, you may need to register for a guest SVN account, or use an existing SVN account and password to download these files directly to your machine. Glade directory paths are relative to /glade/p/cesm/cseg/inputdata/.

Table 1a: Atmosphere + Land

Table 1b: Ocean + Sea ice

Table 2: 1955-2015 Transient Forcing Files

Table 5: Transient Land Forcing :: fsurdat and fpftdyn