The 8th Implementation and Coordination Meeting (ICM-8) of the GCOS Reference Upper-Air Network (GRUAN) was held in Boulder, CO (25-29 April 2016). GRUAN and NDACC have had a long-standing collaboration (dating back to ICM-1 in 2009) that was further formalized by both GRUAN and NDACC becoming Cooperating Networks. NDACC scientists are playing increasingly important roles on the various GRUAN Task Teams and in the development of GRUAN Technical Documents for defining the needs and roles of ancillary measurements from other established networks such as NDACC.
The primary NDACC presentation at ICM-8 was given by Mike Kurylo who focused on recent implementations, activities, and scientific highlights (presented and discussed at the October 2015 meeting of the NDACC Steering Committee) that are pertinent to the growing partnership between the two networks. These included a summary of Data Host Facility issues facing a mature and growing network and the recent interactions between the Theory and Analysis Working Group and the Instrument Working Groups (IWGs) in an effort to provide a bridge between measurements obtained at individual NDACC stations and the global perspective. He pointed out that model simulations by the Theory and Analysis Working Group will help set priorities for network expansion and/or instrument relocation while building on GRUAN RP-4: Outcomes of the GRUAN Network Expansion Workshop. A preliminary work plan from the newly formed Combining Trace Gas Data Theme Group was also outlined.
Of particular interest to GRUAN, was the status of an NDACC-wide Water Vapor Measurement Strategy. Mike listed a number of strategic considerations that are being considered in this development and emphasized that cooperation with GRUAN is essential. While complete instrument duplication within NDACC and GRUAN is probably not necessary, overlap in the "climate critical" region of the atmosphere is essential.
His presentation also focused on the level to which centralized data processing might be achievable for the various NDACC instrument types (Dobson/Brewer, FTIR, Lidar, Microwave, Sondes, UV/Visible, and Spectral UV). This issue is a consideration within the NDACC IWGs, first taking into account unique instrument aspects and their maturities and the potential for algorithm harmonization. Mike discussed the need to balance the positive aspects of such centralization with a number of issues and concerns. He highlighted various activities within each of the IWGs in moving forward, including participation in several international projects focusing on data characterization and harmonization, data processing standardization, and documentation to ensure traceability and consistency. The path forward for a network like NDACC, which certifies many different PI-developed measurement capabilities, is complex. Initial efforts within each IWG continue to focus on the homogenization of data processing and reporting. GRUAN developments and decisions (particularly in the area of the certification of a water vapor data product) will be closely followed.
Complete details about GRUAN and its objective can be found on the GRUAN web site, http://www.dwd.de/EN/research/international_programme/gruan/home.html, where the full agenda for ICM8 can also be accessed. Numerous presentations were given by NDACC scientists or by scientists representing programs that are cooperative with NDACC. Of particular note were updates on the drafting of GRUAN Technical Documents for Lidar measurements (Thierry Leblanc – Lidar IWG), FTIR measurements (Jim Hannigan - FTIR IWG), and Ozonesonde measurements (Jacquie Witte – SHADOZ Representative). Herman Smit discussed progress on the homogenization of ozone records under WMO/GAW and the Ozone Sonde Data Quality Assessment (O3S-DQA) in which both NDACC and SHADOZ have played significant roles. Dale Hurst (NDACC Sonde IWG) spoke about new developments in controlled balloon ascents and descents for improved data acquisition and on the comparison of water vapor measurements from frost point hygrometers and from the Aura MLS satellite instrument. Summaries of field measurement activities at four joint NDACC and GRUAN sites were presented by Marion Maturilli (Ny Ålesund), Rigil Kivi (Sodankylä), Stephanie Evan (Reunion Island), and Richard Querel and Jordis Tradowsky (Lauder). The GRUAN Lead Center is preparing a comprehensive ICM-8 meeting report for future posting on the GRUAN web site. This report will include presentation summaries prepared by the speakers and rapporteurs.