2016-02-29 WIS Metadata Change Monitor

WIS Metadata Changes for GTS Bulletins

Since: 2016-02-17T10Z
Until: 2016-02-29T10Z

Final end of JMA's WMO DDB (Distributed DataBase)

I'm talking about a past service.  If you see the name DDB for the first time, just skip this entry.

Based on the 9th session of the Commission of the Basic Systems, the Japan Meteorological Agency (JMA) had a web (FTP and later HTTP) server called WMO DDB (distributed database) at http://ddb.kishou.go.jp/ .  It contained all sorts of information including realtime data like NWP product and operational information like bulletin catalogue and the routeing table of GTS.

The DDB was shut down on February 2013.  The services are migrated to new locations depending on its nature:

• GISC Tokyo for GSM-related information
• RTH page on GISC Tokyo website for routeing catalogue and bulletin catalogue
• Tokyo Climate Center for climate information

For three years there was a single page notification at the original site http://ddb.kishou.go.jp/ to notify the change.  But it came to the end this time.   The DNS name ddb.kishou.go.jp will be finally removed in several days.  Your understanding and cooperations are highly appreciated.

[WIS] DCPC Tokyo Space Weather Center now serves WIS Metadata through GISC Tokyo

Metadata list

http://www.wis-jma.go.jp/meta/search.jsp?oai_provider=3

[WMO Codes - DRC #293] (to be Validated) New element descriptor for encoding coordinate reference systems (0 01 150: coordinate reference system)

Needs to be checked.

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Issue #293 has been updated by Jitsuko Hasegawa.

• Status changed from ET discussion to to be Validated

Final Report of IPET-DRMM-III 2015 Beijing says:

BUFR allows users to encode coordinates describing where observations were made. However, there is currently no way of encoding the coordinate system in which these coordinates should be interpreted. This allows messages to be encoded with latitude/longitude coordinates which may or may not be understood as the producing centre intended, because the reference coordinate system, and in particular its prime meridian, are left to the user's interpretation.

Since external authorities are not referenced in BUFR tables, the coordinates are ambiguous. Even if it is assumed that the prime meridian at Greenwich is used, this meridian is defined in several coordinate systems with differences of more than 100 meters at most latitudes. In addition to these traditional uncertainties, satellite data sometimes use exotic coordinate systems which cannot be properly interpreted using traditional, geostationary coordinate systems.

Ms Sibylle Krebber, DWD, presented the proposal to define in BUFR messages a coordinate system used and on a note for the case a coordinate system is not defined in a BUFR message.

The meeting agreed to forward to validation stage as shown in the Annex to this paragraph.

Mr Yves Pelletier, Meteorological Service of Canada (MSC) and Mr Alexander Kats, Russian Federal Service for Hydrometeorology and Environmental Monitoring (Roshydromet), supported the proposal and offered to assist validation.

The descriptor forwarded to validation is 0-01-150 Coordinate reference system, with an associated code table.

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DRC #293: New element descriptor for encoding coordinate reference systems (0 01 150: coordinate reference system)

• Author: Jitsuko Hasegawa
• Status: to be Validated
• Priority: Normal
• Assignee: Jitsuko Hasegawa
• Category: BUFR-CREX table
• Target version:

The proposal was made to discuss options to improve coordinates identification, as part of agenda item 3.1(1) of IPET-DRMM-III (#292).

The proposal is the introduction of a new table B descriptor representing Coordinate reference system (0 01 150) with the associated code table.

Document: IPET-DRMM-III Doc 3.1.1

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[WMO Codes - DRC #297] (Future Edition) Encoding elements with a large range and limited precision in BUFR

Quite a big development project.

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Issue #297 has been updated by Jitsuko Hasegawa.

• Status changed from ET discussion to Future Edition

Final Report of IPET-DRMM-III 2015 Beijing says:

Attempts to validate the encoding of wave observations in BUFR have revealed that BUFR does not have adequate facilities for encoding elements which have a large range and limited relative precision. Examples of such elements include, amongst many others, water wave spectral energy densities, pressure in some vertical profiles, concentrations of some atmospheric constituents, and air density.

Dr Weiqing Qu, BoM, presented his document to seek a good solution on this issue.

Several possible solutions were presented, including

a) Use a scale and magnitude representation to allow the required precision for small values without having an excessively large data width

b) Use existing BUFR operators

c) Define a new "Delayed change of scale" operator

d) Encode the logarithm of the element's value instead of the value

e) Use a standard IEEE floating point format

f) Use a "floating point" format, with separate sign, exponent and significand sub-fields

Some comments based on experiences are expressed, which are: when the same issue was discussed, the proposed Table C operator (IEEE floating point) was not adopted, but it should be possible to create operators at least for some cases without change editions; there is in general a lack of compression algorism in BUFR; Météo-France needs some compressions in BUFR for conversion from their internal format to BUFR.

The meeting concluded this issue would be discussed when talking about BUFR edition 5.

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DRC #297: Encoding elements with a large range and limited precision in BUFR

• Author: Jitsuko Hasegawa
• Status: Future Edition
• Priority: Normal
• Assignee: Jitsuko Hasegawa
• Category: BUFR/CREX common aspects
• Target version:

The proposal was made to discuss options to encode elements with a large range and limited precision in BUFR, as agenda item 3.2(5) of IPET-DRMM-III.

Document: IPET-DRMM-III Doc 3.2.5

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[WMO Codes - DRC #291] (Validated) Addition of a new note to GRIB2 code table 3.2 ? Shape of the Earth

This is a step foreward and I consider it harmless, though the discussion is slightly uncomfortable for me --- we can't touch poles, and the humans have had different CRSs with respect to latitude, not only for longitude.

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Issue #291 has been updated by Jitsuko Hasegawa.

• Status changed from ET discussion to Validated
• Target version set to InterCBS2016

Final Report of IPET-DRMM-III 2015 Beijing says:

Several entries in GRIB Code table 3.2 (Manual on Codes, Volume I.2 (WMO-No.306)) specify the shape of the Earth without sufficient information to interpret coordinates, signifying positions on the earth's surface. This allows GRIBs to be encoded with latitude/longitude coordinates which may or may not be understood as the encoding user intended, because the reference prime meridian is left to the user's interpretation.

Ms Sibylle Krebber, Deutcher Wetter Dienst (DWD) presented her proposal, highlighting the issue of ambiguity in a coordinate system used in GRIB messages.

Historically, easting coordinates based on differing easting origins have led to confusion in many circumstances. Although the latitudinal origin is easily defined based on the earth's rotational characteristics, the longitudinal origin is a matter of arbitrary definition, creating the need for the definition and maintenance by an external authority, which are referred in the Code figures 2, 4, 5, 8 and 9 in the Code table 3.2, but the other code figures remain ambiguous.

The meeting reviewed the current Code table 3.2 and agreed that the new note proposed by Ms Krebber will facilitate WMO Members to understand the ambiguity of some coordinate systems in the GRIB Code table 3.2, which is to be approved by the procedure for adoption between CBS sessions as shown in the Annex to this paragraph.

Dr Enrico Fucile offered ECMWF's assistance of the validation.

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DRC #291: Addition of a new note to GRIB2 code table 3.2 – Shape of the Earth

• Author: Jitsuko Hasegawa
• Status: Validated
• Priority: Normal
• Assignee: Eizi TOYODA
• Category: GRIB2 structure
• Target version: InterCBS2016

The proposal was made to add a new note to GRIB2 code table 3.2 – Shape of the Earth, as agenda item 2.1(1) of IPET-DRMM-III, to reduce ambiguity in interpreting coordinates.

Please see linked document for further background.

Proposed additional note
(2) Coordinates can only be unambiguously interpreted if the coordinate reference system in which they are embedded is known. Therefore, defining the shape of the earth alone without coordinate system axis origins is ambiguous. Generally, the prime meridian defined in the geodetic system WGS84 can be safely assumed to be the longitudinal origin. However, because these code figures do not specify the longitudinal origin explicitly, it is suggested to contact the originating center if high precision coordinates are needed in order to obtain the precise details of the coordinate system used.

Document: IPET-DRMM-III Doc 2.1.1

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[WMO Codes - DRC #239] (Validated) GRIB encoding of the beginning of overall time interval in the past

wgrib2 and GRIB-API are treated as de facto reference implementations.

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Issue #239 has been updated by Jitsuko Hasegawa.

• Status changed from ET discussion to Validated
• Target version set to InterCBS2016

Final Report of IPET-DRMM-III 2015 Beijing says:

There are a number of cases where it is desirable to allow the "forecast time" to be negative. These include, but are not limited to, accumulations which start before the reference time during a 4-D variational analysis, which was raised by DWD as agenda item 2.1.2 at IPET-DRMM-II in 2014.

Dr Weiqing Qu, Australian Bureau of Meteorology (BoM), emphasized the risk that some GRIB edition 2 software assumes that the forecast time must be positive regardless of the fact that the regulations do not specify it must be positive. In particular, both wgrib2 and GRIB-API assume that the forecast time is positive and behave incorrectly when a negative value is encoded or decoded.

The meeting recognized the issue critical and reviewed the proposal by BoM. Accordingly, it agreed the new Regulation 92.6.3 to be introduced in GRIB edition 2. A change of wgrib2 and GRIB-API software will be coordinated by the respective responsible developers to conform with the added regulation.

On the other hand, the amendments to each product definition template were not preferred, because regulation is applied to each template and confirmation will be needed when a new template is developed.

The meeting agreed the proposal as shown in the Annex to this paragraph to validate the impact of the new regulation and take the procedure for adoption between CBS sessions, because the risk of comparatively low.

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DRC #239: GRIB encoding of the beginning of overall time interval in the past

• Author: Eizi TOYODA
• Status: Validated
• Priority: Normal
• Assignee: Eizi TOYODA
• Category: GRIB2 structure
• Target version: InterCBS2016

FR IPET-DRMM-II 2014 College Park says:

2.1.2 GRIB encoding of the beginning of overall time interval in the past

DWD needs to encode in GRIB a product which is obtained by a statistical process (accumulation) over a continuous time interval. GRIB Product definition template (PDT) 4.8 seems to be most appropriate for this purpose.

The product is generated at a point in time which is denoted as the reference time, encoded in GRIB Section 1, octets 13-19. The end of the time interval can be encoded using octets 35-41 in PDT 4.8. However, the beginning of the time interval may not be individually defined.

The Note 2 of PDT 4.8 says: The reference time in section 1 and the forecast time together define the beginning of the overall time interval.

The beginning of the time interval may lie in the past with respect to the reference time. In such a case, a negative value must be defined as forecast time (octets 19-22 in PDT 4.8), which is not permitted.

The meeting agreed on necessity to develop this type of representation for negative forecast time and to set up a sub-group. JMA, UK Met Office (UKMO), European Centre for Medium-Range Weather Forecast (ECMWF), DWD and Meteorological Service of Canada (MSC) contribute to the discussion.

Document to the meeting:

• Doc 2.1

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