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The DBCP – GHRSST Pilot Project: an update
How to make a silk purse out of a sow’s ear
(How to make good wine out of bad wine)
David [email protected]
The DBCP – GHRSST Pilot Project: an update
• What is the DBCP?• What does a drifter look like and what does it aim to do?• What is GHRSST?• How can we make drifters perform better for GHRSST?• How can we persuade drifter operators to purchase better
drifters?• How do we ensure continuity?
What is the Data Buoy Co-operation Panel (DBCP)?
• Formed by IOC and WMO in 1985 in response to a crisis:– Ocean Weather Ships had been replaced by drifters– Drifter data quality, quantity and timeliness were very poor– No one understood why– Resolutions etc passed – absolutely no effect on the data!
• Solution: full time technical coordinator appointed in 1987:– Based at CLS Argos in Toulouse within JCOMMOPS office– Access to all parts of the data chain and delayed mode QC
What is the Data Buoy Co-operation Panel?
• Formed by IOC and WMO in 1985 in response to a crisis:– Ocean Weather Ships had been replaced by drifters– Drifter data quality, quantity and timeliness were very poor– No one understood why– Oceanographers did not release their buoy data– Resolutions etc passed – absolutely no effect on the data!
• Solution: full time technical coordinator appointed in 1987:– Based at CLS Argos in Toulouse within JCOMMOPS office– Access to all parts of the data chain and delayed mode QC
• Initial problems solved by 2000
• Develop new initiatives:– Outreach to new observing systems under JCOMMOPS umbrella– Capacity development– Pilot Projects
What is a drifter?
• ‘Standard’ design• Designed to meet needs of both
ocean and met communities• Drogue centred at 15m depth• Pressure ± 1hPa; SST ± 0.2K
Drogue presence detection
• Drogue adds large inertial mass
• Small residual buoyancy
• Buoy submerged for much of the time in rough seas
• Depth of submersion may be >> 1m
• Not a good surface follower
• Submersion sensor used to detect presence/absence of drogue
Drogue loss
Courtesy M Pazos, AOML
What is GHRSST?
• Group for High Resolution Sea Surface Temperature• Formed by GODAE in 2002• Aims to address an emerging need for accurate HRSST
– to constrain the modelled upper ocean circulation thermal structure– for exchange of energy between the ocean and atmosphere
• Generate HRSST products from satellite radiometers• Satellite SST validated against in situ observations using
‘matchups’– Satellite and in situ must be close in space and time– Need to be cloud free– Night-time matchups preferred
• Drifter SST matchups found to be best!• Mean discrepancy < 0.1C
1° 2002-8 zonal mean ARC - buoy diff.
Smoothed 1° 2002-8 avg ARC - buoy diff (°C)
Distribution of ARC - buoy difference (2002-8)
Monthly global area avg ARC - buoy diff and monthly number of ARC/buoy matchup pairs
ARC:D3 SST0.2m
From early test release
Matchup: within 0.1° grid cell, ≤ 3 hrs
Regional discrepancies between drifter and satellite SST
Issues discussed at DBCP in 2010
• Drifter SST clearly critical to satellite SST retrievals!• GHRSST have expanded a DBCP draft proposal to propose a
new joint DBCP-GHRSST pilot project– At least matched funding from GHRSST– 50 drifters upgraded to HRSST reporting– Upgrade cost ~$1k– E-SURFMAR ahead of the game – deploying HRSST-1 drifters– Will require reporting in BUFR to achieve required resolution– Target area to be decided:
• General distribution?• Specific area, e.g. Barents Sea?
• ToRs and workplan agreed• End date 2014• PP-HRSST approved
Immediate plans (2010)
• Need to identify areas that will provide large number of matchups
• These areas to be of interest to buoy operators as they will pay most of the cost
• PP-HRSST funds being used to help Met Office to purchase high accuracy HRSST-2 drifters
• Need to get feedback from GHRSST asap– Problems with receiving BUFR
• Need to get funding from GHRSST
Where are we now?
• 220 HRSST-1 drifters deployed since end 2010– Made by MetOcean, Canada– Deployed by ESURFMAR, Meteo France, UKMO, Env Canada– Mostly N Atlantic – poor matchup statistics because of cloud– Iridium comms + GPS– Hourly reports on GTS in BUFR with resolution of 0.01C– Absolute accuracy ~ 0.1C– Now is default MetOcean design
• 40 HRSST-2 drifters ordered, 3 deployed– Made by MetOcean, Canada– Some upgraded with DBCP funds– Better design for pre- and post-calibration– Absolute accuracy better than 0.05C– Initially cost $1k more
• Still no money from satellite side!
Progress on joint funding
• Make case at GHRSST and ESA meetings • Message now clearly understood
– In situ networks funded in support of NWP, operational oceanography, climate and research: NOT satellite cal/val
– In situ community ready to engage in dialogue and collaborate– Needs sustained funding from satellite community
• GHRSST now seeking sustained funding for in situ HRSST– Drifter HRSST essential– Argo HRSST will be retained as independent verification– Need to fund drifters in ‘high-value’ areas
• ESA Sentinel-3 mission team ready to consider proposal for pre- and post-launch sustained campaign– Draft proposal in prep: target 1 M€ for pre-launch campaign
Drogue presence detection
• Drogue adds large inertial mass
• Small residual buoyancy
• Buoy submerged for much of the time in rough seas
• Depth of submersion may be >> 1m
• Not a good surface follower
• Submersion sensor used to detect presence/absence of drogue
Drogue loss
Courtesy M Pazos, AOML
The good news for GHRSST
• Submersion occurs in higher sea states => well mixed anyway
15 FE B R U A R Y 2002 D O N L O N E T A L .
FIG. 1. Idealized temperature profiles of the near-surface layer (-10-m depth) of the ocean during (a) nighttime and daytime during strong wind conditions and (b) daytime low–wind speed conditions and high insolation resulting thermal stratification of the surface layers.
The good news for GHRSST– drogues fall off!
• Submersion occurs in higher sea states => well mixed anyway• Drogues eventually fall off
– Initially, with drogue on, match-ups may be worse than later on
• Recent data suggests that this often happens within 100 days• Drogue retention has got worse over recent years!• Study by M H Rio: derivation of Ekman parameters as fn of time
β θ
The good news for GHRSST
• Submersion occurs in higher sea states => well mixed anyway• Drogues eventually fall off
– Initially, with drogue on, match-ups may be worse than later on
• Recent data suggests that this often happens within 100 days• Drogue retention has got worse over recent years!• Study by M H Rio: derivation of Ekman parameters as fn of time
β θ
Red line: first 100 days of data only!
The MetOcean HRSST-2 drifter
• Demountable SST sensor to aid pre- and post-calibration• High stability thermistor calibrated to better than 0.05K• Cal coeffs embedded in sensor module• Sensor module sends digital SST to buoy controller• Traceable to national standards
Summary
• Need to identify areas that will provide large number of matchups in shortest possible time
• These areas to be of interest to existing buoy operators as they will pay most of the cost
• HRSST drifters report ONLY in BUFR• Presence of drogue may make things worse• Need to get feedback from GHRSST asap• If worthwhile, need to win follow-on funding through joint
GHRSST/DBCP proposals for:– Further deployments in high value areas– Studies of the near surface temperature profile in the open ocean
