Proposal for new BUFR table entries for Sentinel-6 Michael Freilich

[erget]

Branch

https://github.com/wmo-im/BUFR4/tree/issue-15

Summary and purpose

This document proposes new BUFR entries in order to represent altimeter data from Sentinel-6 Michael Freilich.

Action proposed

The meeting is requested to approve the contents for inclusion within the next update to the WMO Manual on Codes.

Discussions

Sentinel-6 Michael Freilich is due to be launched in the autumn of 2020. In order to ensure the standardized exchange of data from the radiometer mission, a number of BUFR table entries have been developed and are proposed here for adoption.

Detailed proposal

Add the following sequence 3-40-019 “Altimeter product” to BUFR Table D/01:

Table references	Element name
3-40-020	Satellite general values
3-40-021	General radiometer values
3-40-022	Altimeter model values
3-40-023	Altimeter main values

Add the following sequence 3-40-020 “Satellite general values” to BUFR Table D/01:

Table references	Element name
0-01-007	Satellite identifier
0-02-019	Satellite instruments
0-05-044	Satellite cycle number
0-01-096	Station acquisition
0-05-040	Orbit number
0-01-040	Processing centre id code
0-25-061	Software identification and version number
0-25-182	L1 processing flag
0-25-183	L1 processing quality
0-25-181	L2 processing flag
0-25-184	L2 product status
0-08-075	Ascending/descending orbit qualifier
0-25-090	Orbit state flag
3-01-011	Date
3-01-013	Time
0-04-007	Seconds within a minute (microsecond accuracy)
3-01-021	Latitude and longitude (high resolution)
0-05-063	Spacecraft roll
0-05-064	Spacecraft pitch
0-05-066	Spacecraft yaw
0-10-081	Altitude of cog above reference ellipsoid
0-10-082	Instantaneous altitude rate

Add the following sequence 3-40-021 “General radiometer values” to BUFR Table D/01:

Table references	Element name
0-40-012	Radiometer data quality flag
0-08-077	Radiometer sensed surface type
1-04-000	Delayed replication
0-31-001	Delayed descriptor replication factor
0-02-153	Satellite channel centre frequency
0-12-063	Brightness temperature
0-12-065	Standard deviation brightness temperature
0-40-013	Radiometer brightness temperature interpretation flag
0-07-002	Height or altitude
0-11-098	Wind speed from radiometer

Add the following sequence 3-40-022 “Altimeter model values” to BUFR Table D/01:

Table references	Element name
0-08-029	Surface type
2-01-137	Change data width
2-02-129	Change data scale
0-06-021	Distance
2-02-000	Reset scale
2-01-000	Reset width
0-10-087	Ocean depth/land elevation
0-40-024	Meteorological map availability
0-07-002	Height or altitude
0-25-126	Model dry tropospheric correction
0-25-128	Model wet tropospheric correction
0-40-011	Interpolation flag
0-07-002	Height or altitude
0-11-095	U-component of the model wind vector
0-11-096	V-component of the model wind vector
0-10-088	Total geocentric ocean tide height (solution 1)
0-10-089	Total geocentric ocean tide height (solution 2)
0-10-090	Long period tide height
0-10-092	Solid earth tide height
0-10-093	Geocentric pole tide height
0-10-098	Loading tide height geocentric ocean tide solution 1
0-10-099	Loading tide height geocentric ocean tide solution 2
0-10-100	Non-equilibrium long period tide height
0-25-127	Inverted barometer correction
0-40-014	High-frequency fluctuations of the sea-surface topography correc
0-01-030	Numerical model identifier
0-10-085	Mean sea-surface height
0-01-030	Numerical model identifier
0-10-085	Mean sea-surface height
0-10-086	Geoid's height
0-10-096	Mean dynamic topography
0-10-103	Mean dynamic topography accuracy
0-21-169	Ice presence indicator
0-13-055	Intensity of precipitation
0-25-165	Ionospheric correction from model on specific band

Add the following sequence 3-40-023 “Altimeter main values” to BUFR Table D/01:

Table references	Element name
0-25-095	Altimeter state flag
0-40-023	Auxiliary altimeter state flags
0-08-074	Altimeter echo type
3-40-024	1 Hz C and Ku band values
3-40-024	1 Hz C and Ku band values
3-40-024	1 Hz C and Ku band values
3-40-025	20 Hz C and Ku band values

Add the following sequence 3-40-024 “1 Hz C and Ku band values” to BUFR Table D/01:

Table references	Element name
0-22-080	Waveband central frequency
0-08-076	Type of band
0-25-190	Altimeter echo processing mode
0-10-102	Sea-surface height anomaly
0-22-189	Specific band ocean range
0-22-191	Rms of specific band ocean range
0-22-130	Number of valid points for specific band
0-25-167	Specific band net instrumental correction
0-25-163	Altimeter ionospheric correction on ku band
0-15-012	Total electron count per square metre
0-25-164	Radiometer wet tropospheric correction
0-13-090	Radiometer water vapour content
0-13-091	Radiometer liquid content
0-25-166	Sea state bias correction on specific band
0-07-002	Height or altitude
0-11-097	Wind speed from altimeter
0-21-183	Specific band corrected ocean backscatter coefficient
0-21-184	Std specific band corrected ocean backscatter coefficient
0-22-134	Number of valid points for specific band backscatter
0-21-122	Attenuation correction on sigma-0 (from tb)
0-21-186	Specific band automatic gain control
0-21-187	Rms specific band automatic gain control
0-21-188	Number of valid points for specific band automatic gain control
2-01-131	Change data width
0-21-185	Specific band net instrumental correction for agc
2-01-000	Reset width
0-22-179	Specific band significant wave height
0-22-131	Rms specific band significant wave height
0-22-132	Number of valid points for specific band significant wave height
0-22-133	Specific band net instrument correction for significant wave height
0-21-144	Altimeter rain flag
0-25-191	Altimeter tracking mode
0-21-143	Ku band rain attenuation
0-10-101	Squared off-nadir angle of the satellite from waveform data
0-25-112	Band specific altimeter data quality flag
0-25-113	Band specific altimeter correction quality flag
0-33-092	Band specific ocean quality flag

Add the following sequence 3-40-025 “20 Hz C and Ku band values” to BUFR Table D/01:

Table references	Element name
0-08-049	Number of observations
0-22-080	Waveband central frequency
0-08-076	Type of band
0-25-190	Altimeter echo processing mode
1-46-021	Replication
3-01-011	Date
3-01-013	Time
0-04-007	Seconds within a minute (microsecond accuracy)
3-01-021	Latitude and longitude (high resolution)
0-10-081	Altitude of cog above reference ellipsoid
0-10-082	Instantaneous altitude rate
0-08-029	Surface type
2-01-137	Change data width
2-02-129	Change data scale
0-06-021	Distance
2-02-000	Reset scale
2-01-000	Reset width
0-25-191	Altimeter tracking mode
0-21-071	Peakiness
0-01-030	Numerical model identifier
0-10-085	Mean sea-surface height
0-01-030	Numerical model identifier
0-10-085	Mean sea-surface height
0-40-011	Interpolation flag
0-10-088	Total geocentric ocean tide height (solution 1)
0-10-089	Total geocentric ocean tide height (solution 2)
0-25-164	Radiometer wet tropospheric correction
0-07-002	Height or altitude
0-25-126	Model dry tropospheric correction
0-25-128	Model wet tropospheric correction
0-10-102	Sea-surface height anomaly
0-22-189	Specific band ocean range
0-25-167	Specific band net instrumental correction
0-25-163	Altimeter ionospheric correction on ku band
0-21-183	Specific band corrected ocean backscatter coefficient
2-01-131	Change data width
0-21-185	Specific band net instrumental correction for agc
2-01-000	Reset width
0-22-179	Specific band significant wave height
0-22-133	Specific band net instrument correction for significant wave height
0-22-146	Ocog range
0-21-189	Corrected OCOG* backscatter coefficient
0-13-163	Snow water equivalent
2-02-126	Change data scale
0-22-046	Sea ice fraction
2-02-000	Reset scale
0-13-117	Snow density (liquid water content)
0-13-013	Total snow depth
0-25-112	Band specific altimeter data quality flag
0-25-113	Band specific altimeter correction quality flag
0-33-092	Band specific ocean quality flag

Add the following elements to BUFR Table B/40:

Descriptor	Name	Units	Scale	Reference	Width
0-21-189	Corrected OCOG* backscatter coefficient (negative reference)	dB	2	-32768	16
0-22-179	Specific band significant wave height (negative reference)	M	3	-500	16

Notes:

• 0-21-189 is similar to 0-21-177, but with a negative reference value
• 0-22-179 is similar to 0-22-190, but with a negative reference value

[jbathegit]

Hi Daniel - a reminder that Y > 191 means a descriptor is local, so your proposed new FXY numbers 0-21-192, 0-22-192 and 3-40-192, 3-40-193, ..., 3-40-198 all need to be adjusted to put them into the WMO standard range where Y <= 191.

[erget]

Hi Jeff, yes, you're right - the thought here was that there might be number clashes so we'd discuss the sequences and then when they're ok have the Secretariat assign the final numbers.

[SimonElliottEUM]

It was a cunning plan on my part. It doesn't matter which numbers we get - I though it might be helpful to have them assigned by the Secretariat

[marijanacrepulja]

Hi Daniel,
Many thanks for BUFR templates.

• Could we not include satellite name in the name of the BUFR template since the same template will be used for other altimeters.

• Would't it better if the following elements are moved from the "3-40-197 “Sentinel-6 Michael Freilich 1 Hz C and Ku band values" part to the "3-40-194 “Sentinel-6 Michael Freilich radiometer values" part:
  0-25-164 Radiometer wet tropospheric correction
  0-13-090 Radiometer water vapour content
  0-13-091 Radiometer liquid content

• In 3-40-195 why do we have twice
  0-01-030 Numerical model identifier
  0-10-085 Mean sea-surface height

• In 3-40-194, could we use delayed replication. That is in case that we can re use it in the future.

• If element "0-21-122 Attenuation correction on sigma-0 (from tb)" is new, can we change sigma-0 to backscatter coefficient to be consistent with the other elements like: "0-21-183 Specific band corrected ocean backscatter coefficient"

[erget]

Hi @marijanacrepulja , I've answered your questions point-by-point below:

Could we not include satellite name in the name of the BUFR template since the same template will be used for other altimeters.

This is fine, I have updated the sequence names accordingly.

Would't it better if the following elements are moved from the "3-40-197 “Sentinel-6 Michael Freilich 1 Hz C and Ku band values" part to the "3-40-194 “Sentinel-6 Michael Freilich radiometer values"...

Those descriptors are proposed for 3-40-197 because the retrieved values use the radiometer brightness temperatures and the altimeter's Sigma0, so they should remain in that sequence.

...why do we have twice 0-01-030 ... 0-10-085

The product will contain 2 MSS models in the product, this is to allow describing both of them.

In 3-40-194, could we use delayed replication

Yes, I have updated the sequence accordingly.

If element "0-21-122 Attenuation correction on sigma-0 (from tb)" is new, can we change sigma-0 to backscatter coefficient to be consistent with the other elements like: "0-21-183 Specific band corrected ocean backscatter coefficient"

0-21-122 already exists, we would prefer to reuse it.

[chenxiaoxia2019]

@erget Hi, Daniel, I changed the FXY number of Corrected OCOG* backscatter coefficient (negative reference) from 0-21-192 to 0-21-189 and changed the FXY number of Specific band significant wave height (negative reference) from 0-22-192 to 0-22-179. And, I also changed from 340192 to 340018, 340193 to 340019, 340194 to 340020, 340195 to 340021, 340196 to 340022, 340197 to 340023, 340198 to 340024. More information about the CREX_Unit, CREX_Scale, CREX_DataWidth_Char, Status are needed. A branch for this issue is created. Please check it. Many thanks.

[erget]

@chenxiaoxia2019 I note the following changes:

• 0-21-192 to 0-21-189
• 0-22-192 to 0-22-179
• 3-40-192 to 3-40-018
• 3-40-193 to 3-40-019
• 3-40-194 to 3-40-020
• 3-40-195 to 3-40-021
• 3-40-196 to 3-40-022
• 3-40-197 to 3-40-023
• 3-40-198 to 3-40-024

and have updated the proposal accordingly.

I'm a bit confused about the CREX information - this is satellite data and thus we don't intend to disseminate it in CREX. What do you require exactly?

[erget]

@chenxiaoxia2019 I have reviewed the proposed changes in the associated PR. I didn't review every file but rather BUFR_TableD_en_40.csv and txt/BUFRCREX_TableB_en.txt but of course the changes in those files will need to extend to the other ones as well.

[erget]

@chenxiaoxia2019 I note also that there is a number clash in these tables - #10 already uses 3-40-018. I propose giving the IKFS-2 sequence described in that issue to use 3-40-023 but I leave it to you to make the final decision that will not produce a number clash.

For now, I'm producing sample data as described in this proposal, i.e. #10 and #15 are both using different definitions for 3-40-018.

[erget]

I've uploaded sample data - *.nc is the native file, *.bin is the same translated into BUFR.

[marijanacrepulja]

@chenxiaoxia2019
BUFR_TableD_en_40.csv still contains entries that need to be updated, please see below
40,Additional satellite report sequences,340018,(Altimeter product),,340193,Uuu,,,Operational
40,Additional satellite report sequences,340018,(Altimeter product),,340194,Vvv,,,Operational
40,Additional satellite report sequences,340018,(Altimeter product),,340195,www,,,Operational
40,Additional satellite report sequences,340018,(Altimeter product),,340196,Xxx,,,Operational

[erget]

I've corrected the issues found on the associated branch; it looks fine to me now.

[marijanacrepulja]

@erget I also found that lines below need to be updated
40,Additional satellite report sequences,340022,(Altimeter main values),,340023,Yyy,,,Operational
40,Additional satellite report sequences,340022,(Altimeter main values),,340023,Yyy,,,Operational
40,Additional satellite report sequences,340022,(Altimeter main values),,340023,Yyy,,,Operational
40,Additional satellite report sequences,340022,(Altimeter main values),,340024,Zzz,,,Operational

[efucile]

replace 3-40-018 with 3-40-xxx before validation of samples

[erget]

I have renamed 3-40-018 to 3-40-019, giving precedence to #10.

[erget]

Hi @marijanacrepulja I've uploaded new sample data, can you please re-confirm?

[marijanacrepulja]

Hi @erget, please see attached output of decoded sample. I have used table D from branch but haven't been able to check values, as there is no file to show what the decoded values should be.

W_XX-EUMETSAT-Darmstadt,SURFACE+SATELLITE,S6A+P4+L2+HR_C_EUMS_20170305065123_F01_000_000_20170305065238.bin_decoded.txt

I have now noticed with real numeration assigned, that template 3-40-023 “Altimeter main values” contains repetition of 3-40-24 three times. Could you please explain the reason.

I have request from our Research Department if could be possible to include 20-Hz wind speed values (21 of them).
Many thanks

[erget]

@marijanacrepulja thank you very much!

The repetition of 3-40-024 is due to the use of 3 different algorithms: SAR, LRM & PLRM. This was agreed (prior to my involvement!) with colleagues from ECMWF, I believe in R&D, but I'm not sure who was involved.

Also, although we have space in the sequence for including 20-Hz wind speed values, these are not present in the original product - Sentinel-6 doesn't produce them. That's why you don't see them in these BUFR messages.

Is there anything else we should discuss or can we consider the product validated?

[marijanacrepulja]

@erget I believe we can consider the product validated. Thank you for the feedback.

[erget]

Perfect, thank you, then I am marking this template as validated.

[amilan17]

SUMMARY: Add entry to Table B Class 21, add entry to Table B Class 22 and add entries to Table D Category 40.

[amilan17]

Approved by FT 2020-2.