VOSClim Elizabeth Kent1, Sarah North2, Scott Woodruff3 and David Berry1 1: National Oceanography Cen

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VOSClimElizabeth Kent1, Sarah North2,Scott
Woodruff3 and David Berry11 National
Oceanography Centre, Southampton, UK2 Met
Office, Exeter, UK3 Earth System Research
Laboratory, NOAA/OAR, Boulder CO, USA
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VOSClim Talk Outline

• What is VOSClim?
• How does it work?
• Why do we need it?
• What have we learnt?
• What about the future?

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What is VOSClim?

• VOSClim is a JCOMM pilot project aiming to
  improve the quality of marine meteorological
  observations from Voluntary Observing Ships
  (VOS)
• VOSClim aims to produce a high quality dataset
  from a subset of VOS which can be used in climate
  research
  
• VOSClim ships are standard VOS, which happen to
  provide good quality reports, we are not
  equipping them with higher quality instruments

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What is VOSClim?

• VOSClim tries to do this by
• Recruiting ships with good reporting records
• Asking Port Meteorological Officers (PMOs) to
  visit the VOSClim ships more frequently
  
• Getting the full Pub. 47 metadata
• Asking for pictures of the ship and instruments
• Monitoring the data received to higher standards
• Archiving the ship report with co-located
  forecast model output
  
• Reporting extra parameters to try and understand
  the data

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How does VOSClim work?

• The participating countries recruit their best
  VOS to VOSClim
  
• A detailed survey of the ship and its instruments
  is made, photos taken and metadata collected
  
• The reports from the VOSClim ships are extracted
  by the Met Office from the GTS datastream
  
• The Met Office append co-located forecast model
  output to the report
  
• VOSClim ships have tighter monitoring limits
• The reports are sent to NCDC for archive
• NCDC maintain the archive of VOSClim
  reports/model output/additional parameters and
  maintain the VOSClim website
  
• www.ncdc.noaa.gov/oa/climate/vosclim/vosclim.html
  

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Why do we need VOSClim?

• Some of the problems with VOS meteorological
  reports are well known.
  
• Bucket SSTs are usually too cold
• Historically Engine Intake SSTs were too warm
• Visual winds need adjustment
• Screen humidities are too high
• Daytime air temperatures are too warm
• But the ships still provide information we cannot
  currently get in any other way

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The importance of ship data
Data Requirement Monthly mean heat flux to
10Wm-2 (WGASF, 2000). Air temperature, humidity
and winds all inadequate. SST adequate in most
regions, but other requirements, for example for
high resolution products, will probably show SST
data also inadequate.
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High-quality surface fluxes from VOS

• VOS are are only source of in situ flux data
  distributed over the ocean.
  
• In well sampled regions (typically northern
  mid-latitudes and major shipping lanes) we can
  make daily estimates of air-sea exchange.
  
• We need to make sure we have both the QUALITY and
  QUANTITY of data we need.

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VOSClim and VOS

• Numbers of ships with 10 SST reports in 2004
• VOS 2300 (or 500 360 obs)
• VOSClim 100
• VOS and VOSClim ships are similar ships using the
  same instrumentation
  
• VOSClim ships selected for their good reporting
  record
  
• VOSClim has recruited about 20 of the ships
  which report regularly
  
• VOS and VOSClim are converging as VOS numbers
  decline
  
• The total number of reports is becoming a major
  issue

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Ship Reporting 1980 and 2004

• In 1980 there are many more ships making a
  relatively small number of observations than in
  2004
  
• In 2004 we have fewer ships overall, but a higher
  proportion make more reports, often hourly
  
• A higher proportion of ships have associated
  metadata in 2004 than in 1980

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What Have We Learnt?

• The number of ships participating in VOSClim is
  smaller than we had hoped (about half the target
  minimum of 200) ....
  
• The VOSClim analysis data is fairly small
• There have also been problems with the data flow
  and archival
  
• The transmission formats necessary to transfer
  the additional parameters have only just been
  ratified by JCOMM-II
  
• But a paper has been published in the CLIMAR-II
  special issue of Int. J. Climatology on the
  effect of instrument exposure on VOS air
  temperature measurements

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Air Temperature Sensor Exposure
Paper Berry, D. I. and E. C. Kent, 2005 The E
ffect of Instrument Exposure on Marine Air
Temperatures An Assessment Using VOSClim Data
International Journal of Climatology (CLIMAR-II
Special Issue), 25(7), 1007-1022.
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What about the future?

• For VOSClim to succeed we need to recruit more
  ships
  
• But the pool of VOS available is shrinking, in
  2004 2300 ships made identifiable SST reports,
  and of these only about 500 made a substantial
  contribution
• The adequacy analysis shows our knowledge of most
  in situ marine meteorological fields is
  declining
  
• The dataset must be analysed
• Identify and promote good observing practice
• Develop corrections to data where necessary
• Produce estimates of data requirements (quantity
  and quality) for VOSClim and VOS

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VOSClim needs your help

• The early years of VOSClim have been taken up in
  getting the project set up and the data flowing
  
• But VOSClim now needs to produce scientific
  results
  
• We are looking for people to join a "VOSClim
  Scientific Users Group"
  
• Minimum required input is to participate in email
  discussions on scientific issues for VOSClim (and
  VOS)
  
• But more involvement is encouraged, and
  necessary, if VOS and VOSClim datasets are to
  meet the needs of marine climatology