GCOS/WCRP Working Group on Observational Data Sets For Reanalysis

4th WCRP Observations and Assimilation Panel Meeting

Hamburg, Germany, March 29-31, 20101

GCOS/WCRPWorking Group on

Observational Data SetsFor Reanalysis

Vose et al.



4 Terms of Reference

• Review data center holdings worldwide

• Develop a plan for integrated data sets

• Oversee progress of Implementing Centers

• Report regularly to AOPC and WOAP



• The Working Group has …– Assembled surface and upper air data set inventories– Augmented existing data sets– Developed plans for improving specific data sets– Focused on upcoming reanalyses– Served as a catalyst (e.g., NCDC wouldn’t have done…)

• The Working Group has not …– Denoted “official” Implementing Centers (loose confederation

has generated products thus far)– Held many meetings (one in Tokyo; e-mail and phone calls

otherwise; Trenberth encourages proposal for another)

Generalities



Dataset Activities

• 20th Century Reanalysis (C20R)– International Surface Pressure Databank (ISPD)– International Comprehensive Ocean Atmosphere Dataset– International Best Track Archive for Climate Stewardship

• Other data set activities (for ECMWF, etc.)– C20R datasets listed above– Integrated Global Radiosonde Archive (IGRA)– Satellite products (Bates, Zou, etc. encourage me to credit

these activities to the working group, but that’s a stretch; still, the data sets do benefit reanalyses…)



C20R Support

~0500 UTC Jan. 22, 1918 (ISPD)

~0000 UTC Jan. 22, 1918 (C20R)



Surface Pressure: ISPD 2.2.4

• GCOS/AOPC/OOPC Surface Pressure Working Group

• Identify, retrieve, digitize, merge, QC• Some numbers:

– 33 data sources– 33,653 stations– 1.7 billion obs– 1768-2008

• V3 in late 2010



Marine Data: ICOADS 2.5

• Surface reports from ships, buoys, other platforms

• SST, pressure, humidity, etc.

• 1662-2007, with preliminary updates thereafter

• Many new historical sources digitized



• 1st central repository, world’s largest archive

• 14 source datasets (including all RSMCs)

• ~10,000 storms from 1840-present

Tropical Cyclones: IBTrACS 2.0

1848-2008

1907-2007

1945-2007

1945-2007 1949-

2007

1851-2007



Other Dataset Activities

• Integrated Global Radiosonde Archive (IGRA)

• Satellite products– SSM/I and SSMIS (NCDC, CSU, NESDIS/STAR)– MSU/AMSU (NESDIS/STAR et al.)



Notables:- v1 done in 2005

- v2 underway

- 42 source datasets (vs. 11)

- All reformatted

- Merging in process (no eta)

Upper Air Data:Integrated Global Radiosonde Archive

(IGRA)

Variables:- pressure

- geopotential height

- temperature

- dew point depression

- wind direction/speed

IGRA v1

IGRA v2



SSM/I and SSMIS

• Extended/improved period of record (1987-present)

• Completed in 2010, freely available from NCDC

• Fundamental climate data record effort by CSU and NESDIS/STAR is ongoing

• High-quality but proprietary RSS product still available for purchase



NESDIS/STAR MSU/AMSU

• V2 SNO out• 1979-2009• TIROS-N to

NOAA-18, MetOp-A

• V1 used in CFSR, MERRA



Reviewing theTerms of Reference

-- Slides with “?” = more feedback, please --



Need Feedback On …

• CCl partnership• More data set development work• Radiosonde temperature metadata• Better BUFR capability• Web-based catalogue• Working Group meeting• Other suggestions



Term of Reference #1

• Review:– The holdings of data centres worldwide … for

observations suitable for use in reanalysis or in observational studies.

– The opportunities for enhancement of these holdings through data recovery, collection, and reprocessing.

• Thoughts:– Well intentioned but works better when driven by a

specific need (e.g., C20R).– Somewhat related to Met Office proposal to CCl on

International Analysis of Land Surface Air Temperature (hold comments until next slide)



Partnership with CCl?

• Participation in workshop on Creating Surface Temperature Datasets to Meet 21st Century Challenges (preferably with a broader mandate)

• Real-time monitoring of synoptic reports by the working group (information passed to CCl, which in turn can encourage more reporting by individual countries – helps future reanalyses)



Continue Other Review Efforts?

• Focus on upcoming surface-only reanalyses by ECMWF and NOAA– Implies surface pressure (ISPD) and other primary

surface elements (Integrated Surface Dataset)

• Maybe a little more on the radiosonde record (ERA-CLIM)– Implies more work on IGRA



Term of Reference #2

• Develop a plan for … data sets:– Merging of holdings … incorporating metadata …– Development … of standards, version control, software …– Identification … of an Implementing Centre … for data sets

…– Extension of data sets in close to real time …– Maintenance and publication of a catalogue … of data sets

…

• Thoughts:– We have developed data sets instead. This will continue.– Some radiosonde temperature metadata work is needed.– More work on standards is possible, but it’s tough.– The time has come for the data set “catalogue.”



• When there were breaks, how big they were, how certain

• Include both documented and inferred changes

• Also include observation minus background (MERRA, C20R…)

• Basically give the assimilation system more information

• Or even try to homogenize (recommendation from SDS workshop, Microwave group)

Sonde Temperature Metadata?



• Universal formats are useful• As are nice interfaces to those formats• Can manage both input data and

feedback• Tedious to develop• Diverging opinions within the working

group on this

Better BUFR Capability?



• “A compilation, updated regularly, would be a major service.”

• What there is, where it is, how to get it• WG members can volunteer what they

know, provide contacts• Keep our pulse on the latest and greatest

for each data set• Hosted at NCDC• Alternative to the “Implementing Centre”

Web-Based Catalogue?



Small, Focused Workshop

• Working group members and selected others

• Add-on to another meeting– 3rd ACRE workshop: Reanalysis and Applications and the

U.S. Reanalysis/IESA workshop in Baltimore, MD (Nov. 2010)

– But those two meetings take up 5 days already

• Funding may be available through WOAP• Key issues are how our activities relate to

and take advantage of current reanalyses• Again, feedback welcome



Reanalyses Suitable for Characterizing Long-Term Trends: Are They Really

Achievable?P.W. Thorne and R.S. Vose

Reanalyses are, by a substantial margin, the most utilized climate data products, and they are applied in a myriad of different contexts. Despite their popularity, there are substantial concerns about their suitability for the monitoring of long-term climate trends. This has led to calls for a truly “climate quality” reanalysis that retains long-term trend fidelity. The authors contend that for such a reanalysis to be achieved, a substantial rethinking of the current strategy for producing reanalysis products is required. First, the problem must be defined clearly. Second, the methodology that is employed must be reconsidered so as to minimize potential nonclimatic artifacts and robustly ascertain the inevitable residual uncertainty. Finally, a set of validation data and metrics must be constructed that the community can use to compare and unambiguously assess the claims of climate quality. The purpose of this essay is very much to initiate discussions to this end rather than to prescribe solutions.

(To be published in BAMS, March 2010)

GCOS/WCRP Working Group on Observational Data Sets For Reanalysis

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