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NCEP ADP Global Upper Air and Surface Weather Observations
(PREPBUFR format) are composed of a global set of surface and upper
air reports operationally collected by the National Centers for
Environmental Prediction (NCEP). These include land surface, marine
surface, radiosonde, pibal and aircraft reports from the Global
Telecommunications System (GTS), profiler and US radar derived
winds, SSM/I oceanic winds and TCW retrievals, and satellite wind
data from the National Environmental Satellite Data and Information
Service (NESDIS). The reports can include pressure, geopotential
height, temperature, dew point temperature, wind direction and
speed. Report time intervals range from hourly to 12 hourly.
These data are the output from the PREPBUFR processing performed at
NCEP, which is the final step in preparing the majority of
conventional observational data for assimilation into the various
NCEP analyses including the North American Model (NAM) and NAM Data
Assimilation System (NDAS) unified grid-point statistical
interpolation (GSI) analysis (the "NAM" and "NDAS" networks), the
Global Forecast System (GFS) and Global Data Assimilation System
(GDAS) unified grid-point statistical interpolation (GSI) analysis
(the "GFS" and "GDAS" networks), the Rapid Refresh (RAP) unified
grid-point statistical interpolation (GSI) analysis (the "RAP"
network), the Real Time Mesoscale Analysis (RTMA) unified grid-point
statistical interpolation (GSI) analysis (the "RTMA" network), and
the Climate Data Assimilation System (CDAS) spectral statistical
interpolation (SSI) analysis (the "CDAS" network).
This step involves the execution of series of programs designed to
assemble observations dumped from a number of on-line decoder
databases, encode information about the observational error for each
data type as well the background (first guess) interpolated to each
data location, perform both rudimentary multi-platform quality
control and more complex platform-specific quality control, and
store the output in a monolithic BUFR file, known as PREPBUFR. The
background guess information is used by certain quality control
programs while the observation error is used by the analysis to
weigh the observations. The structure of the BUFR file is such that
each PREPBUFR processing step which changes a datum (either the
observation itself, or its quality marker) records the change as an
"event" with a program code and a reason code. Each time an event is
stored, the previous events for the datum are "pushed down" in the
stack. In this way, the PREPBUFR file contains a complete history of
changes to the data throughout all of the PREPBUFR processing. The
most recent changes are always at the top of the stack and are thus
read first by any subsequent data decoder routine. It is expected
that the data at the top of the stack are of the highest quality.
The data provided here are also available in NetCDF and ASCII
formats, which can be accessed by following the "Get a subset" link
on the ds337.0 data access page
[https://rda.ucar.edu/datasets/ds337.0/#!access]. The NetCDF
datafiles are converted from PREPBUFR format using the pb2nc utility
in the Model Evaluation Tools (MET) software package.
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