The NA-CORDEX data collection comprises output from different
regional climate models (RCMs) at various spatial resolutions driven
by the ERA-Interim historical reanalysis and by different global
climate models (GCMs) using different representative concentration
pathways (RCPs) for the future composition of the atmosphere. The
various combinations of RCM, GCM, RCP, and spatial resolution that
have been simulated are shown in
the Simulation Matrix.
The NA-CORDEX data collection archives output from these
simulations for a number of variables of interest to end users,
especially those who work with climate change impacts. The full
list of variables is available on
the Variable List page.
Each variable is stored at the daily timescale. The collection also
includes monthly, seasonal, and annual averages of each variable, as
well as monthly and seasonal climatologies (multi-year averages). In
addition, the archive also includes sub-daily precipitation at the
highest frequency available.
The model outputs are stored on the native grid used for
simulation, which has a consistent spatial resolution across the
simulation domain. In addition, the archive also includes a version
of each dataset that has been interpolated to a common lat-lon grid
at roughly equivalent spatial resolution. The interpolation has
been performed using
the ESMF
"Patch" algorithm.
The archive also includes bias-corrected version of each GCM-driven
dataset. These datasets have been adjusted using a multivariate
quantile-mapping method
(Cannon's MBCn
algorithm) against a gridded daily observational dataset. Most
impacts users find bias-corrected data more useful than the raw
model outputs. See below for more details.
Each data file in the NA-CORDEX collection is named
"[var].[scen].[gcm].[rcm].[freq].[grid].[bc].nc". The components
vary as follows:
- var: Variable
See the variable list for names
of variables. We have published all essential and high-priority
variables, as well as some aspirational variables.
- scen: Scenario
ERA-Interim runs are given a scenario named "eval" (for
evaluation) for the sake of regularity. The historical ("hist")
scenario runs 1950-2005; future (RCP-based) scenarios run
2006-2100.
- gcm: GCM (driver)
The source of the boundary conditions for the RCM. Usually a GCM,
but includes the ERA-Interim reanalysis.
- rcm: Regional Climate Model
- freq: Temporal frequency
Sub-daily data is available only for precipitation for certain
RCMs. "ymon" and "yseas" are multi-year climatological
averages.
- grid: Grid and spatial resolution
The grid names follow the CORDEX convention for domain naming.
The NAM-44, NAM-22 and NAM-11 indicate 0.44°, 0.22°, and
0.11° native rotated-pole grids, respectively; the "i" suffix
indicates that the data has been interpolated to a common
half/quarter/eighth-degree lat-lon grid. RegCM4 and WRF
simulations with a grid value of 44 or 22 are actually using a
50-km or 25-km projected grid, which is roughly equivalent in
resolution to the 0.44° and 0.22° grids.
- bc: Bias-correction
"Raw" data is uncorrected model output. "MBCn" data has been
bias-corrected using Cannon's MBCn algorithm against
the gridMET
or Daymet gridded
observational datasets. The gridMET dataset uses climatically
aided interpolation to blend data
from PRISM with
data from the
NLDAS-2
reanalysis; it includes surface winds, but only covers CONUS. The
Daymet dataset interpolates and extrapolates GHCND station data
using purely statistical methods; it does not include surface
winds but covers the entire United States, Canada, and Mexico.
Both datasets include tmin, tmax, precip, specific humidity, and
incoming solar radiation. We also derive relative humidity and
tmean (the average of tmin and tmax) from other variables.
NOTE: A previous bias-correction ("mbcn-METDATA") has been
deprecated; it used an older version of gridMET and had a sign
error in the surface winds.
