Representatives:

• Dennis Keyser (lead), NCEP
• Jeff Ator, NCEP
• Mike Barth, FSL
• Keith Brewster,OU/CAPS
• Geoff DiMego, NCEP
• James Drake, AFWA
• Patty Miller, FSL
• Keith North, AFWA/IBM
• Barry Schwartz, FSL
• Francois Van den Berghe, NCAR

Overview of area of focus, objectives and strategies

The observational data play a vital role in correcting the evolution of the forecast model at the assimilation times, validating the performance of the dynamical model and assimilation system, and assessing the quality of the various data types. Effective use of data for these purposes requires the establishment of a database equipped to catalog the statistics comparing the observations, analysis, and forecast, stratified according to data types. It is important that the format of the database be well documented.

The data handling must be designed to incorporate data over a wide variety of platforms and it must be able to perform multi-platform rudimentary quality control, including bounds checking. In addition, the data handling must be designed to accept new platform-specific quality-control steps, as well as upgrades to existing codes, as they become available. The manner in which each datum is treated by objective quality-control procedures should be recorded, as well as the manner in which aggregated data (super-observations) are constructed. It is expected that all multi-platform quality control functions will be performed in the 3D-VAR.

In coordination with WG#4 and WG#9, it was decided late last year that NCEP would be the source of processed observations for the initial versions of the WRF 3D-VAR analysis. NCEP has access to all the world's observations and processes those observations on a continuous 24x7 basis. The output format of the operational NCEP decoder and data ingest suites is the WMO standard BUFR. This database provides the superset of information for the network-specific pre- processed and quality-controlled BUFR files which are read by the 3D-VAR. These files are called "PREPBUFR". Current PREPBUFR data sets will be available for download by WRF users via public servers. Another huge advantage is that PREPBUFR data sets are also available from the 50-year NCAR/NCEP global reanalysis project for use by WRF researchers.

The 3D-VAR interface to the PREPBUFR files is accomplished through a library of utilities (BUFRLIB) which NCEP is providing, along with documentation for their use. The interface subroutines in the 3D-VAR could easily be linked to other utility libraries in order to read data ingested in formats other than BUFR (e.g., NetCDF at FSL and SQL at AFWA).

NCEP has provided online documentation on its current observational data processing including data decoding, data dumping, and platform-specific quality control steps in the PREPBUFR environment at http://www.emc.ncep.noaa.gov/mmb/papers/keyser .

The working group met for the first time at NCEP last January. Present were Dennis Keyser/NCEP, Patty Miller/FSL, Mike Barth/FSL, Jim Drake/AFWA, Jeff Ator/NCEP and Bill Collins/NCEP.

The NCEP representatives discussed the current data processing suites at NCEP. Jeff Ator discussed the decoding and ingest of GTS data. Dennis Keyser discussed the ingest of satellite data, the dumping of data, and the PREPBUFR pre-processing and platform-specific quality control steps. Bill Collins discussed the complex quality control programs for radiosonde, wind profiler, and VAD wind data in detail. Documentation on all aspects of the NCEP data processing, including a glossary of several of the more common BUFR interface routines from the NCEP BUFRLIB, was distributed.

Initially, the WRF 3D-VAR will be able to read existing NCEP PREPBUFR files (including those from the 50-year reanalysis project), or files in other formats which are passed through the BUFR-look-a-like interface.

The current PREPBUFR format will eventually be upgraded to:

• combine mass and wind information from the same report (currently these are split into two "reports")
• add new quantities in existing data types as needed by the 3D-VAR
• add new data types as needed by the 3D-VAR
• convert all data to WMO standard descriptors where possible
• refine the existing report types to allow for more specific platform/instrument
• assignments (the current PREPBUFR file contains observation error information specific to the report type)
• improve the means by which new data types could be appended to existing PREPBUFR files
• add new, and upgrade existing, platform-specific quality control steps (the multi-platform quality control is expected to be included in the 3D-VAR)
• complete the recording of observation "events", especially those added by the PREPDATA program
• explore the option of having separate PREPBUFR files, based on data type, available to the 3D-VAR rather than a monolithic file as is the case now (this could take advantage of the multi-processing features of the 3D-VAR)

July 2001 (NCEP, FSL)

New data sources are added to current PREPBUFR files. These data types include

• GOES cloud-top pressure
• GPS integrated precipitable water
• MESONET surface data

(Note: Other new data sources will continue to be added as they become available and are tested.)

October 2001 (NCEP)

The PREPBUFR file is modified to combine mass and wind reports and to use standard WMO descriptors where possible.

November 2001 (NCEP)

Software is provided allowing a user to select observation type, domain, time window and other subsets from the global version of the PREPBUFR file.

July 2002 (Group)

New datasets that may not necessarily exist in BUFR are added to the database. Interface software is written which allows the 3D-VAR to read these data.

Resources (NCEP only)

Since the WRF observation processing is essentially the NCEP operational obs processing, the amount of additional activity and resources required has been kept to a minimum.