Arctic System Reanalysis (ASR)
NCEP PREPBUFR FILE:
The PREPBUFR file contains all observational data used to construct NCEP analyses and historic reanalyses. The PREPBUFR data record spans the period: 1948-2007 and is approximately 500Gb (0.5 Terabyte) in size. PREPBUFR data are stored in “self-describing” files, meaning that header data/tables are included at the beginning of each file explaining the potential types of data that may be included in that particular file. The format is a compressed byte structure that can be decoded (and encoded) by standard FORTRAN or C programs. Some useful subroutines are availabe from NCEP to facilitate the conversion to and from ASCII to the BUFR format. Observations are collected and archived from various observing platforms: surface station, upper-air rawinsonde, aircraft, ship, satellite, fixed and driftin buoys, profiler and other field programs. The data sources are identified in the PREPBUFR by a data-source-type ID. Some of these data-source-type IDs are listed here: (http://www.emc.ncep.noaa.gov/mmb/data_processing/prepbufr.doc/table_3.htm). Each observation's associated space/time coordinates are also noted as latitude, longitude, elevation and time relative to a six-hour period (the temporal resolution of the PREPBUFR archive). Observed variables are archived separately for mass (temperature, pressure, mixing ratio, etc.) and wind variables.
Most of the observations in the PREPBUFR file contain associated quality markers. The data quality markers are used by NCEP in producing analyses/reanalyses by weighting one or more observations based on their quality. The code table for the quality markers is here: (http://www.emc.ncep.noaa.gov/mmb/data_processing/prepbufr.doc/table_7.htm)
During quality control and preprocessing of the PREPBUFR observations, decisions are made that may modify an observation and/or associated quality marker. A history of these modification “events” is provided with each observation so that changes in an observation can be noted and tracked. An example table of some of the “reason codes” used to describe modification events is here: (http://www.emc.ncep.noaa.gov/mmb/data_processing/prepbufr.doc/table_8.htm)
SAMPLE PREPBUFR CONTENT:
Sample output:
ADPSFC
ADPUPA
SFCBOG
AIRCAR
SFCSHP
AIRCFT
SATEMP
SATWND
Observation header information includes:
Station ID
Longitude
Latitude
Time (in hours before the 6-hour reference time)
Elevation
T1, T2, T3 (Type codes - decoded by a table - see links above)
Observations include:
ob : Observation
qm : Quality mark
pc : Program code
rc : Reason code
fc : Forecast value
an : Analysis value
cat : Office note category
"lv" indexes the levels of the report
"jj" indexes the modification event stacks
"kk" indexes the variable types (p,q,t,z,u,v)
The plots below show one week inventories of observations included in the PREPBUFR file categorized by observation type (e.g., surface station, upper air station, satellite wind, etc.) Dates are 01/01/2003 - 01/07/2003 at 6-hour intervals.
Choose individual graphics below for a more detailed image. |
ADPSFC
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ADPUPA
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AIRCAR
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AIRCFT
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SATEMP
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SATWND
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SFCBOG
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SFCSHP
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The quicktime animation below shows all observation locations, color coded by observation type (e.g., surface station, upper air station, satellite winds, etc.), included in the PREPBUFR file for one week plotted for six hour periods. Dates are 01/01/2003 - 01/07/2003 at 6-hour intervals.
Choose individual graphics below for the quicktime animation. |
