November, 2007

     1. The original ADS GCMS instruments at Mace Head and Cape Grim were retired
        in December 2004, and replced by new generation of improved GC-MS system.
        The new GC-MS cryogenic preconcentration system, which we called Medusa
        have been installed in five (Macehead, Trinidad Head, Barbados, Samoa, 
        and Cape Grim) AGAGE sites. This new Medus GC-MS system has much better 
        capability to measure most volatile and radiatively active perfluorinated 
        compounds.

     2. Most of archived GC-MS-Medusa data (up to March 2007) are calibrated
        to the latest SIO-2005 scale. 

     3. Archived data are saved in the follwoing three folders
        (a) complete   -- all high frequency mesurements with pollution flags
                          (identified by "P" after reported mole fractions (ppt))  
        (b) monthly    -- monthly means of backgound values at 5 AGAGE sites
        (c) precisions -- instrument precision files