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GFDL SPEAR Large Ensembles

Model and simulations

The SD Division at GFDL has conducted 30-member ensembles of climate change simulations over the period 1921-2100 using the SPEAR_MED climate model (Delworth et al., 2020). Selected output from these model runs is available as described below. This model has a 50 km atmosphere/land horizontal resolution and an approximate 1° horizontal resolution for the ocean and sea ice components. Simulations extend from calendar year 1921 to 2100, and are forced with historical radiative forcings over the period 1921-2014, and the SSP5-8.5 projected radiative forcings (O’Neill et al., 2016; van Vuuren et al., 2013) for 2015-2100. For further details on the design and simulation aspects of the ensembles see sections 2.4.3 and 3.4 of Delworth et al., 2020

Data access

The model output files are in netCDF form, and variable names correspond to CMIP6 conventions (Juckes et al., 2020). Some data is available on a daily basis, whereas other data is available as monthly means. For monthly data, each variable is contained in a single file for the period 1921-2014, and a separate file for the period 2015-2100. These two files are under separate directory structures as described below. For daily data there are 10 years worth of data per file (only 4 years for the 2011-2014 period), so that there are 10 files for the period 1921-2014. For the period 2015-2100 there are 9 files total: 10 years per file except for 6 years for the period 2015-2020. Data for the period 1921-2014 is under the “historical” directory as explained below, and data for 2015-2100 is under the “scenarioSSP5-85” directory. Data resolution is 360 x 576 on a latitude/longitude grid.

ftp access

To download data via ftp, do the following from a terminal window: 

        >>ftp (log in as anonymous with your email address as the password)


From that point one can ‘cd’ into either the “historical” directory (model output from 1921-2014) or the “scenarioSSP5-85” directory (model output for 2015-2100).

Under each directory there are 30 ensemble members. For example,  the “rXXi1p1f1” directory contains output from ensemble member “XX”, where “XX” varies from “1” to “30”. Below that point directory “Amon” contains atmospheric monthly data, and directory “day” contains atmospheric daily data. 

For a particular variable, such as surface air temperature (“tas”), ‘cd’ into directory “tas/gr3/v20210201”. The data for surface air temperature (“tas”) is in file “”

In this case the monthly (denoted by ‘Amon’) surface air temperature (denoted by ‘tas’) is from ensemble member 10 (denoted by ‘r10’) over the period 1921-2014 (192101-201412).

The files “areacella” and “areacello” contain grid-cell area information for all atmospheric and ocean variables (the cell areas are a constant for the model grid, and thus are “static” and do not vary in time). The files are the same for all ensemble members, and so are only located with the first ensemble member in both the historical and scenarioSSP58-5 directories: r1i1p1f1/fx/areacella/gr3/v20210201/ and r1i1p1f1/Ofx/areacello/gr/v20210201/.

Example script

The following text is an example of the contents of a bash script that can be used to download the monthly tas ensemble member 1 variable from the historical experiment.

#directory to save files
#GFDL large ensembles ftp site
#enter ${outdir} directory
cd ${outdir}
#download file with wget command
wget ${ftp_site}/historical/r1i1p1f1/Amon/tas/gr3/v20210201/

Available variables

Variable Long name Frequency
tas Near-Surface Air Temperature day, Amon
ta Air Temperature Amon
tasmin Daily Minimum Near-Surface Air Temperature day
tasmax Daily Maximum Near-Surface Air Temperature day
pr Precipitation day, Amon
hus Specific Humidity Amon
psl Sea Level Pressure day, Amon
zg Geopotential Height Amon
sfcWind Near-Surface Wind Speed Amon
uas Eastward Near-Surface Wind day, Amon
vas Northward Near-Surface Wind day, Amon
ua Eastward Wind Amon
va Northward Wind Amon
rlut TOA Outgoing Longwave Radiation Amon
rsut TOA Outgoing Shortwave Radiation Amon
rsdt TOA Incident Shortwave Radiation Amon
tos Sea Surface Temperature Omon
areacella Grid-Cell Area for Atmospheric Variables fx
areacello Grid-Cell Area for Ocean Variables Ofx


When using this data please acknowledge as downloaded from GFDL using, with a publication reference to  ‘SPEAR: The Next Generation GFDL Modeling System for Seasonal to Multidecadal Prediction and Projection’, Delworth et al. (2020), Journal of Advances in Modeling Earth Systems, 12, e2019MS001895,


Please direct questions to with “SPEAR Large Ensembles” included in the subject line.