NCEP/NCAR Global Reanalysis Data Archive Information
Revised: 30 May 2023
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Access -
The NCEP/NCAR Reanalysis archive may be accessed by using a ftp client or
by a web browser:
1) If you want to use a ftp client, Windows PC users may use WinSCP, FileZilla,
etc. that support passive mode. MacOS and Linux users may use the ftp
command. Connect your ftp client to ftp.arl.noaa.gov using anonymous and
your email address for the username and password, respectively and change
directory to /archives/reanalysis. Note if you are using multiple
ftp connections, limit the number of concurrent connections equal to or
less than two. Otherwise, your access to our ftp server may be blocked off.
2) If you are using a web browser, point it to
https://www.ready.noaa.gov/data/archives/reanalysis.
It may take a few minutes or longer for the webpage to display.
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Overview -
The NCEP/NCAR Reanalysis Project is a joint project between the National
Centers for Environmental Prediction (NCEP, formerly "NMC") and the National
Center for Atmospheric Research (NCAR). The goal of this joint effort is to
produce new atmospheric analyses using historical data (1948 onwards) and as
well to produce analyses of the current atmospheric state (Climate Data
Assimilation System, CDAS). Until recently, the meteorological community has
had to use analyses that supported the real-time weather forecasting. These
analyses are very inhomogeneous in time as there have been big improvements in
the data assimilation systems. The quality and utility of the re-analyses
should be superior to NCEP's original analyses because:
* a state-of-the-art data assimilation is used
* more observations are used
* quality control has been improved
* the model/data assimilation procedure remains unchanged during the project
* many more fields are being saved
* global (some older analyses were hemispheric)
* better vertical resolution (stratosphere)
More information about the reanalysis project and data are available from
several sources:
https://wesley.wwb.noaa.gov/reanalysis.html
https://www.cdc.noaa.gov/cdc/data.nmc.reanalysis.html
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Availability -
A subset of this data is available from ARL in a format suitable for transport
and dispersion calculations using HYSPLIT through READY by selecting
"Reanalysis" in the meteorological data set selection pull-down menu.
The archive is updated on this site once per year at the end of the year.
The directory contains data files with the following syntax:
R{S|P}{YEAR}{MONTH}.{gbl|tbd}
Where R indicates "Reanalysis", S or P indicates that the data are on Sigma or
Pressure surfaces, YEAR is a four digit year, and MONTH is a two digit month.
The file suffix identifies the projection as either the 2.5 degree global
latitude-longitude projection (gbl), or a regional conformal map projection.
Other regional projections are "to be determined (tbd)" later. The projection
details are encoded in the file's index record and are processed by HYSPLIT
during trajectory or dispersion computations.
The sigma level data were obtained from NCEP's internal spectral coefficient
archive. The pressure level data were obtained from the NOAA-CIRES Climate
Diagnostics Center, Boulder, Colorado, USA.
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Additional Data Set Details
Pressure Level Data
2.5 degree latitude-longitude global grid
144x73 points from 90N-90S, 0E-357.5E
1/1/1948 - present with output every 6 hours
Levels (hPa): 1000,925,850,700,600,500,400,300,250,200,
150,100,70,50,30,20,10
Surface or near the surface (.995 sigma level) winds and temperature
Precipitation
Model Type: LAT-LON
Vert Coord: 2
Numb X pt: 144
Numb Y pt: 73
Numb Levels: 18
Sfc Variables: 5 PRSS T02M U10M V10M TPP6
Upper Levels: 6 HGTS TEMP UWND VWND WWND RELH
Sigma Level Data (CONUS extract for the DATEM archive, not available)
The spectral coefficients on 28 model sigma surfaces were processed
to obtain required fields 4 per day on a global Gaussian grid of
1.875 degree resolution. A regional sub-grid covering the continental
US and Canada was extracted.
Current USA spatial domain: 21.9N 127.5W to 60.0N 52.5W
Output every 6 hours
Levels: .995,.982,.964,.943,.916,.884,.846,.801,.751,.694,.633,
.568,.502,.436,.372,.312,.258,.210,.168,.133,.103,.078,
.058,.042,.029,.018,.010,.003
MODEL TYPE: MERCATOR
VERT COORD: 1
POLE LAT: 21.904
POLE LON: -127.5
REF LAT: 21.904
REF LON: -127.5
REF GRID: 136.5
ORIENTATION: 0.
CONE ANGLE: 0.
SYNC X: 1.
SYNC Y: 1.
SYNC LAT: 21.904
SYNC LON: -127.5
NUMB X: 57
NUMB Y: 41
NUMB LEVELS: 29
SFC VARIABLES: 01 PRSS
UPPER LEVELS: 05 TEMP SPHU UWND VWND WWND
