the homogenization and reporting of groundbased atmospheric datasets for the validation of earth...
TRANSCRIPT
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HDF and HDF-EOS WorkshopNovember 30, 2006
The Homogenization and Reporting of Groundbased Atmospheric Datasets for the
Validation of Earth Observing Satellite Instruments - the Aura and Envisat validation
approach using HDF
B. R. Bojkov, NASA-GSFC (USA)
R. M. Koopman, ESA-ESRIN (I)
M. De Maziere, BIRA-IASB (B)
I. Boyd, NIWA (NZ)
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HDF and HDF-EOS WorkshopNovember 30, 2006
Outline
• Context (and some history)
• Implementation for Envisat and Aura
• Future activities
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HDF and HDF-EOS WorkshopNovember 30, 2006
• Why did we do this for atmospheric sciences?
(from the perspective of validation)
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HDF and HDF-EOS WorkshopNovember 30, 2006
• Ensuing from European Arctic campaigns in the 1990’s
• ~35 stations reporting» operational NRT and scientific
• All stations uses NASA-Ames» “simple” ASCII
• More than 18 file variations» nomenclature and formulations
• Clear need of homogenization
Near-real-time ozonesondes
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HDF and HDF-EOS WorkshopNovember 30, 2006
The problem is accentuated:
• Different measurement networks» LIDAR, MWR, FTIRs, UV-Vis instruments, etc.
• Different platforms» Groundbased, aircraft, balloon, ship, in-situ, etc.
• Different agencies» “Dialog” across timezones, reporting facilities, etc.
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HDF and HDF-EOS WorkshopNovember 30, 2006
So, in 1996/1997…
• Near impossible to use effectively for research or tools/RDB/web implementations
• Need to resolve this “file reporting ” problem by investigating/understanding the state of affairs in the field
• First objective: satellite validation of atmospheric chemistry instruments» up and coming ESA and NASA missions
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HDF and HDF-EOS WorkshopNovember 30, 2006
COSE
• COSE - Compilation of atmospheric Observations in support. of Satellite measurements over Europe
• European Commission (EC) funded project
• Consortium of 25 groundbased and satellite teams
• Timeline: 1998-2000
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HDF and HDF-EOS WorkshopNovember 30, 2006
COSE (2)
• Approach:» Investigated existing file formats, usage, community needs
in consultation with the different stake-holders
• Recommendations:» Defined fixed file formulation: HDF4 (SDS)» Rigid metadata, including strict guidelines for attributes
requirements, variable naming, etc.» Make files truly homogeneous and self explanatory» Final document by Bojkov et al., 2002 (available through
AVDC)
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HDF and HDF-EOS WorkshopNovember 30, 2006
Basic HDF4 SDS file layout
• Global attributes: 31 attributes» Data source / contact information» Dataset contents / location / …» File generation date / version / caveats / …
• Attributes for each SDS: 19 attributes» Variable description / notes / caveats» Dependencies / dimensions» Units / SI conversion factor / Valid min. & max. / Fill values» Display attributes (label, axis, …)
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HDF and HDF-EOS WorkshopNovember 30, 2006
Global attributes
Variable attributes
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HDF and HDF-EOS WorkshopNovember 30, 2006
Variable naming convention
• Variable name construction: 3 part construction
VARIABLE_NAME + VARIABLE_MODE (+ VARIABLE_DESCRIPTOR)
• Example: » The variable name for O3 measured by an O3sonde and a Brewer spectrometer are:
O3_CONCENTRATION for the ozonesondeO3_VERTICAL.SOLAR for the Brewer in direct sun modeO3_VERTICAL.ZENITH for the Brewer in Umkehr mode
» The RMS for a FTIR ozone measurement can be expressed as:
O3_VERTICAL.ZENITH_UNCERTAINTY.RMS
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HDF and HDF-EOS WorkshopNovember 30, 2006
Similar conventions for
• Attribute entries
• Instrument naming
• File names
• …
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HDF and HDF-EOS WorkshopNovember 30, 2006
First Implementation: ESA
• Spring 2000: ESA Envisat mission was is it’s final validation planning:» 10 instruments, focus on land, atmosphere and oceans.
• ESA required:» Fully relational database for calibration and validation» File “QA/QC” on all incoming files» Specifically COSE concept, including HDF 4, to be
implemented for atmosphere and ocean instrument validation
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HDF and HDF-EOS WorkshopNovember 30, 2006
Envisat Cal/Val
• Implemented in October 2000» Meets all ESA requirements, including QA and the RDB» 200+ users, intercontinental participation» Backbone of the coordinated validation efforts of 3
atmospheric and 2 ocean instruments» Data sources collected from ship-based to satellites» Extended to other Envisat/ESA validation activities (2004)
• One issue: heterogeneous reporting- the ozonesonde problem was back!
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HDF and HDF-EOS WorkshopNovember 30, 2006
2004-present
• EOS-Aura validation activities
• The Network for Detection of Atmospheric Composition Change (NDACC - former NDSC)
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HDF and HDF-EOS WorkshopNovember 30, 2006
Aura Validation Data Center
• Support the NASA EOS-Aura mission» 4 atmospheric instruments» troposphere to mesosphere measurements» Share validation communities with Envisat
• AVDC uses the same concept/approach as Envisat» Maintain Envisat files compatibility
• Operational since October 2004» ~300 users - many new participants» ~2TB validation data
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HDF and HDF-EOS WorkshopNovember 30, 2006
AVDC modifications
• Refined file and metadata requirements through thorough analysis of Envisat Cal/Val in early 2004» Eliminate common user errors and misconceptions» Added HDF5 implementation (user request due to HDF5 satellite
data)
• Implemented rigid measurement reporting templates» Collaborative effort with NDACC» Measurement specific and defined by expert community» Results in truly homogeneous files
• Document describing changes by Bojkov et al., 2006 available through AVDC web site
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HDF and HDF-EOS WorkshopNovember 30, 2006
Future of the AVDC/Envisat implementation
• AVDC refinements are being implemented into Envisat Cal/Val
• AVDC/Envisat format being phased into NDACC network» LIDAR, MWR, FTIR completed
• AVDC concept to be extended to NASA A-train (and most probably NPP wrt validation data)
• Format is ESA requirement for ESA/EC GMES program» To be extended to land and radar altimetry
• NASA and ESA to remain synchronized
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HDF and HDF-EOS WorkshopNovember 30, 2006
Closing remarks
• This type of work takes time» Began in 1998, and will be ongoing
• Requires proactive involvement by all parties» Validation teams, instrument PIs, satellite teams, …
• Requires rigid guidelines - down to the measurement level
• Once implemented, it is extremely useful for all involved as experienced for the Envisat and Aura missions when validation relies on very different data sources
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HDF and HDF-EOS WorkshopNovember 30, 2006
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