Instructions

View the instructions below for for reproducing - protocol and forcing information

CESM Code Tag

The Large Ensemble Community Project (LENS) and the Last Millennium Ensemble (LME) simulations used a common CESM1.1 code base.

The LENS tag was preserved as a special CESM tag:

cesm1_1_2_LENS

The Last Millennium Ensemble (LME) was not maintained as a dedicated CESM tag. The instructions linked below outline how to reproduce the Last Millennium 850AD control and 850AD-2005 control simulations from a CESM1.1 or CESM1.2 release tag.

Instructions

850AD Control

850AD-1849 Transient Last Millennium

Initial Conditions

Initial conditions among ensemble members were varied using round off error introduced through the CAM namelist. OCN/ICE/CLM/RTM initial conditions were held constant.

Setup instructions

The Last Millennium code base was not preserved as a special CESM tag. However, the instructions listed below can be used to reproduce the Last Millennium 850AD control and 850AD-1849 control simulations. We also include instructions for extending the Last Millennium through the 20th Century.

The input datasets needed for these simulations 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/

Forcing files 850AD; 850-1849; 1850-2005

The forcing files are available on NCAR's glade:

/glade/p/cesm/cseg/inputdata

Many of the filenames listed in the tables below are also linked to the SVN input data repository or to other data centers. To gain access the NCAR files you may 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/

SOLAR FORCING: The solar forcing uses the reconstruction of Vieira, Solanki, Krivova, and Usoskin (Vieira et al., Astron. Astrophys.,2011) for total solar irradiance with the spectral variations and '11-year' solar cycle from Schmidt et al., (Geosci. Model Dev., 2012).

The input datasets are available on NCAR glade filesystem:

/glade/p/cesmdata/cseg/inputdata/atm/cam/solar/SOLAR_SPECTRAL_VK_Lean_849-2008_annual_c130909.nc

VOLCANIC FORCING: For the LM volcanic forcing, we adopt the ice core–based index of Gao et al. (J. Geophys. Res, 2008), which is based on volcanic deposition signals from 54 ice core records from both the Arctic and Antarctica. This reconstruction provides estimates of the stratospheric sulfate aerosol loadings from volcanic eruptions, modeled as a function of latitude, altitude, and month. The twentieth-century simulation uses an eruption dataset of similar temporal and spatial resolution as described by Ammann et al.(Geophys. Res. Lett.,2003) and used in CMIP5 twentieth-century simulations

GREENHOUSE GAS FORCING: The LME evolution of the concentrations of the principal long-lived greenhouse gases (GHGs; CO2, CH4, and N2O) are imposed based on estimates from highresolution ice cores in Antarctica [see Schmidt et al. (Geosci Model Dev., 2012) for discussion and references]. Small variations from 850 to about 1800 are related to natural feedbacks in the carbon and nitrogen cycles.

LAND USE/LAND COVER BOUNDARY CONDITIONS: In the LM simulation, we merged the Pongratz et al. (2008) reconstruction of land use, proposed by PMIP3, with that of Hurtt et al. (2009) used in the CCSM4 twentieth-century simulations to give a consistent and smoothly evolving land use change. The datasets are spliced together by scaling the Pongratz et al. (Global Biogeochem. Cycles. 2008) dataset to match the Hurtt et al. (iLeaps Newsletter, 2009) dataset at 1500 for every land model grid point. The only plant functional types (PFTs) that are changed are those for crops and pasture; all other PFTs remain at their 1850 control prescription.

Note: The surface dataset used for the 20th Century extensions (1850-2005) of the LM simulations was modified for members 002-008

• Ensemble member 001: fsurdat = surfdata_1.9x2.5_simyr1850_c110114.nc
• Ensemble members 002-008: fsurdat = surfdata_1.9x2.5_simyr1850_c140303.nc

ORBITAL FORCING: The CESM model adjusts orbital position (eccentricity, obliquity and precession) automatically every model year through the coupler namelist variable (orb_iyear) based on Berger et al., (J. Geophys. Res.,1993).

AEROSOL FORCING: Stratospheric aerosols are prescribed in the model as a fixed single-size distribution in the three layers in the lower stratosphere above the tropopause

OZONE FORCING: The ozone forcing is from WACCM, not SPARC. For the 1850 control run ozone was specified as a repeating annual cycle based on an existing WACCM 300-yr control run. For the transient historical period (1850-2005) we use the average of 2 existing WACCM ensemble members and apply a 10-year running mean to each month separately.

The input datasets are available on NCAR glade filesystem:

/glade/p/cesm/cseg/inputdata/atm/cam/ozone