Please see here for the full list of participants.

For the agenda and links to the presentations please go to: http://metportal.dwd.de/mol → GRUAN.

Session 1 - Introduction
Opening of the Meeting
Franz Berger the Chair of the meeting welcomed participants and opened the sessions at 8.30 on Tuesday 26 February 2008.

DWD - the host of GRUAN lead center by Wolfgang Kusch
The Director of DWD, Wolfgang Kusch gave a background briefing on DWD, its goals and strategies for the next few years, until 2015.

• Improved quality of weather prediction,

• Improved long term atmospheric observations on climate monitoring,

• Strong research development.

He noted that a GRUAN lead centre has been established at Lindenberg, staff selected and first staff member started on 1st February. Other staff will start in May 2008.

Tour of the Observatory
There was a visit to the calibration laboratory, where the instruments calibrated include radiosondes.
The participants were informed there would be an Intercomparison Campaign of Radiosondes at Lindenberg in November 2008. HMEI will contact the manager at the site to ensure all HMEI member manufactures are invited.

Opening Addresses

• There was an opening address by Ulrich Kasparich, the Federal State Secretary BWVBS.

• In a short opening address, David Goodrich, GCOS, thanked the participants for attending.

Overview of GRUAN by Peter Thorne and David Goodrich  See this report here
This noted:

• GRUAN has until now been a largely abstract concept;

• It will consist of 30-40 sites;

• Providing a high quality climate data record

• Will be run for climate monitoring (not NWPs)

• Summarized finding from the first two GRUAN meetings;

• Noted that the GRUAN Report (WMO TC 112) has a summary of the first two reports.
  

• The overall structure of the organizational structure of GRUAN;
• The main overseeing body to be the AOPC (anologous to the AOPC on GSN and GUAN)
• The Working Group (WG) on Atmospheric Reference Observations responsible to the AOPC;
• Lindenberg Observatory as the first and lead GRUAN station;
• The WG has a list of suggested other initial stations;
• The WG to research/propose additional stations.

Some proposals for the meeting from the overview:

• Formulate a set of guidelines for procedures and instrumentation;
• Ensuring compatibility of observations;
• Resolution of issues on instrumentation;
• Formulate a set of guidelines for data dissemination and QA/QC;
• Look at the potential need for multi-instrument redundant systems.

SESSION 2 - Initial Site Selection
Reviews of Current Networks
Presentations were given of each of the following:

• Lindenberg
• ARM - 3 core sites and one mobile station
• Lauder - New Zealand
• Howard University (specialising in Radiosonde comparisons)
• European site selection, particularly Cabauw in Netherlands and a suggestion of an Australian site
• Pallas-Sodankylä - Finland
• Boulder - USA
• Chinese potential sites, particularly Xilinhot
• Tropical Site candidates
• SHADOZ (Southern Hemisphere Additional Ozonesondes) - tropical and sub-tropical sites

  SHADOZ issues

:
The lack of quality staff
Training
Equipment supply;
Radiosondes not funded locally, but by foreign aid.

Partnership/Mentoring Programme by Franz Berger

• Some sites could act as mentors to other sites with less knowledge/expertise.
        - The meeting seemed to find this proposal doubtful.
•  Financial support from partners.
       - The meeting thought this would be difficult to achieve.

SESSION 3 - Radiosonde Instrumentation and Launch Schedule
Radiosonde Instrumentation Issues and Challenges by Holger Voemel

• Pressure - some small internal temperature lag occurs
• Temperature - various errors pointed out
• Water-vapour
       - No current sensor comes close to GRUAN requirements,
       - Polymer sensors - overall there are many errors which need to be overcome to make them useful for GRUAN,
       - Vaisala polymer sensor best commercially available, but still not up to GRUAN requirements,
       - CFH reference sonde has best polymer sensor, but is not commercially available.

Rational for using current best operational radiosondes by Doug Sisterson

• The operations and quality control procedures at ARM Climate Research Facility were used to demonstrate potential effectiveness of this approach.
• Best operational instruments are needed for GRUAN.
• Feedback between GRUAN and manufacturers would be crucial.

Rational for using reference Radiosondes by June Wang
This presentation outlined the problems in using any current, operational, Radiosonde. With current sondes uncertainties in measurements (particularly in temperature and humidity) were perceived as being of the same magnitude as the changes necessary to be identified to establish the trends.

Therefore reference Radiosondes that can achieve the standards required would need to be developed. The challenges for creating such reference sondes are that they need:

• To be robust, accurate, affordable;
• Careful designing of package (to ensure quality data collection);
• Traceability to NIST and other standards + good metadata; 
• Inter-comparisons of multiple sensors and systems;
• Real time QM and post data QC;
• Effective communications to all stakeholders.

The details of perceived problems and standards GRUAN would hope to achieve in Radiosonde measurements can be found here in the presentation.

Discussions on GRUAN Radiosonde requirements:

• The majority view was that the current operational Radiosondes do not meet GRUAN requirements.
• There was a suggestion from the floor that perhaps manufacturers could work together to create a single standard reference Radiosonde for use in climate research.

Framing the Question of GRUAN Sonde Launch Schedule by Dian Seidel
Two options:
                 1) Fixed launch schedule - gives data homogeneity and continuity; OR
                 2) Coordinate launches with satellite overpass - gives best calibration data for homogenizing satellite observations.

It is possible to have a mixture of these two options, which gives information for climate process investigation.

Rational of coordination with satellite overpass by Carl Mears
Although using GRUAN for calibration of microwave sounding satellites would seem to be a useful process there are problems. Coordination of overpasses with sonde launches  is difficult, as a satellite pass is instantaneous, whereas a sonde profile is spread over 1 hour or more. The magnitude of differences this causes is not able to be accurately known.

Rational for a fixed schedule by Kevin Trenberth
This presentation endorsed the establishment of a new global baseline network of “reference” radiosondes. The purpose of the reference sondes would be:

• To create an anchor and baseline reference point that does not require bias correction for assimilation and comparison with all other observations.
• To create a climate data record in its own right at that location.
• The latter can be achieved only for a fixed schedule of regular synoptic observations.

The presentation concluded that there is no sense to collocate sonde launches with satellite overpasses. A better way would be to make use of analysis (4D-Var), which takes into account all observations and errors.

SESSION 4 - Instrumentation and Observing Practices
Keynote speech - Ground based instrumentation requirements by John Nash
Dr Nash discussed the experiences of the MET Office's Demonstration "Test" Site at Camborne, UK, for consideration by the meeting in looking for the instrumentation for GRUAN.

The Camborne site includes a Next Generation Upper-Air Network, the benefits of which are to:
    - Optimize current network with surface and weather radar;
    - Meet User Requirements (i.e. Higher spatial and temporal resolution);
    - Reduce costs or deliver more for similar cost.

Dr Nash's presentation discussed the benefits and rational of  ground based remote sensing and gave a list of instrumentation being considered for Camborne:
    - Microwave radiometer
    - Infrared spectrometer
    - GPS water vapour
    - Wind profiler, UHF
    - Optical Doppler Lidar
    - Laser ceilometer
    - Cloud radar
 
The presentation summarized that:

• Ground based remote sensing is required in future upper air networks
• Design of networks needs to be based on a knowledge of mesoscale structure and the associated atmospheric structures
• Error characteristics of the remote sensing observations must be established by data assimilation techniques
• Improved operational practices need to be developed and are not yet readily available
• It is recommended that test-bed experiments be used to develop the necessary knowledge
• CIMO/WMO will sponsor experiments

Dr Nash also presented some of the latest developments in radiosondes, from 4 manufacturers. He noted, quoting results from the Intercomparison for High Quality Radiosondes in Mauritius, that there are several manufacturers now creating equally high-quality operational Radiosondes.

Instrumentation Presentations were also given on: Vertical Profiles, Practical Problems in Implementation of Instruments; GPS measurements and MeteoSwiss Surface and Upper-air Developments; by D. Engelbart, R. Boers, J. Wang and B. Calpini, respectively

Discussion minimum requirements of instruments for GRUAN stations:
A minimum requirement of GPS, microwave radiometer, Raman Lidar, as well as basic reference radiosondes, was discussed, but no final decision was made.

There was a discussion as to whether pilot project stations were necessary to find the best solutions for GRUAN stations. However David Goodrich suggested that it would be better to start a network of stations rather than starting with pilot projects, which would take too long.

Introduction to "Suitability of current WMO regulatory documentations, such as Manual and Guide on the GOS and WMO Guide to Meteorological Instruments and Methods of Observation" by Miroslav Ondrás
This presentation put forward a proposal for the documentation required by GRUAN to be based on the WMO system of Manuals and Guides. This would include site selection, instrumentation requirements, QC, traceability and other various aspects such as coding and formats.

SESSION 5 - Data dissemination and QC/QA
Requirements for quality control/quality assurance by Doug Sisterson
This presentation identified how QA/QC is set up in ARM, which has multiple laboratories across the USA. The procedures are bases on web applications. A description was given of how this system inspects the data checks each data stream, identifies problems, finds out why data is missing, produces a daily data quality report that lists problems found and solved (or not). The reports are linked to the original data in the archives, so users can see the full data including the quality reports metadata.

This was followed by a presentation on Added Value Products in ARM by Jennifer Comstock.

SI (International System of Units) Traceability of Measurements by Tom Gardiner
This considered the issue of traceability of measurements and the metrology framework and the need to:
    - To provide national support for metrology,
    - Provide international comparability and traceability of measurements.
It was stated that measurements may not need to be tied to SI (International System of Units), but to accepted and traceable standards.

Data Analysis/Fusion and Uncertainty Issues by Alastair Forbes
This presentation was a detailed technical discussion on aspects of data evaluation in regard to precision, trueness, bias, interoperability of measurement systems, repeatability and reproducibility, and the design of experiments to assess these factors.

Utility of Raw Radiosonde Data in QA/QC by Alexander Kats
Dr Kats looked at the potential of using raw data in Quality Control, as only raw data could provide the possibility of adequate reprocessing, if calibration, correction or software problems occurred. He noted that close cooperation between manufacturers, scientists and operational staff was necessary for this.

Integrated Profiling of the Atmosphere by Reinout Boers
This presentation outlined the Integrated Profiling Technique (IPT); an advanced method to synergize Columnal Observations for climate monitoring.

Requirements for Data Dissemination:
The next part of SESSION 5 saw presentations from Steve Williams from the NCAR Earth Observing Laboratory in Boulder, USA; and Matthew Menne from the NOAA National Climatic Data Center, Asheville, USA.; and Holger Voemel from the Cooperative Institute for Research in Environmental Sciences, Colorado, USA;

These presentations looked at the experiences of data dissemination and management from the Coordinated Energy and water-cycle Observations Project (CEOP) and the GCOS Lead Centers, and posed the question "should data be freely available and accessible?". It was considered that probably some data, such as Radiosonde data, could be freely available, but from specialised instruments it probably should be restricted, as the principal investigator needs some time to work with his data and publish any results he may have. Then the data could become free.

SESSION 6 - Coordination with other International and National Activities
Presentations were given on the activities of several other international systems and networks, including GSICS, GEOSS, GAW and NDACC, BSRN, and from the national agencies of Netherlands, Russia, USA and China. These presentations also gave in information on input and/or potential station sites for GRUAN. Links to these presentations are available from the meeting agenda available at: http://metportal.dwd.de/mol → GRUAN.

Bruce Sumner also gave a short presentation, informing the meeting about the Association of HMEI.

SESSION 7
Development of an Action Plan - by Peter Thorne
This presentation summarized: the criteria for what was needed for a station to be considered worthy to be a GRUAN station; the initial sites for GRUAN; and the action plan to achieve GRUAN.

Minimum requirement (priority 1) of a GRUAN station given in the GCOS report:

• Standard surface variables (pressure, temperature, humidity and wind)
• Simultaneous balloon-based observations of temperature, water vapour and winds, both on ascent and descent Note: not stipulated as to frequency
• Pressure and GPS/radar height of balloons
• Ground based GPS receivers to measure total column water vapour
• Stations do not need to be "Lindenberg equipment rich" to join but there does need to be an undertaking to move in that direction as funds permit over time.

Ground based instrumentation/observing practices:

• Need GPS PW to be GRUAN site
• Recommend at least one additional radiometer
• Practices need to be sufficiently standardised to be able to inter-compare

Radiosonde instrumentation and observation:

• Radiosonde scheduling requirement:
  - 1 x weekly reference sonde,
  - 1 x monthly cluster (CFH, Snow White and RS92)
  - Regular soundings (00+12)
• Avoid vendor lock-in
  - periodic Intercomparisons

Unresolved radiosondes issues:

• Scheduling and development of a reference Radiosonde - a small team to work on this.
• Suggestion for another comparison of radiosondes to choose which are suitable to be used for GRUAN, with a deadline of 2010, to be done by Lead Center, Working Group on Atmospheric Reference Observations (WG-ARO) and CIMO.
• Dr Nash suggested that GRUAN requirements for Radiosondes be specified, so that GRUAN sites can chose from amongst Radiosondes known to meet these requirements.
• Dr Ondrás suggested a compromise: to select some sondes for weekly benchmarking, this to not be locked-in, but would be re-evaluated with future Intercomparisons.

• Lauder, Payernne, Boulder
• Xilinhot, Beltsville, Potenza
• Cabauw, Lindenberg, 3 ARM (Alaska, Darwin, Central Plains), Sodankyla
• South Pole.

Other Matters:

• The first draft of manual/guides for GRUAN is due by January 2009.
• A mentoring program to spread best practices will be organised by the Lead Center.

Close of Meeting
The meeting closed at 17.30 on Thursday, 20 February 2008.

Update - WMO Field Intercomparison of Rainfall Intensity (RI) Gauges at Vigna di Valle, Italy
There will be a meeting of the participants in the Intercomparison and local staff, at Vigna di Valle, 21-22 May 2008.

The participating manufacturers will be there, of which the majority are HMEI member manufacturers. See the list of participating instruments and manufacturers at: http://www.hydrometeoindustry.org/InterComparisons.htm#WMO_Combined_Intercomparison_of_Thermometer
_Screens/Shields_in_Conjunction_with_Humidity_Measuring_Instruments_Ghardaïa,_Algeria,_beginning_2007_–_2008_. 
Bruce Sumner and Christine Charstone from the HMEI Secretariat have also been invited and will attend the two day meeting.

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