June, 2012 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. In addition to original 5 AGAGE stations, the Jungfraujoch and Zeppelin (Ny-Alesund) stations becomes part of AGAGE stations in 2011. They use the same instrument and calibrations as other original AGAGE stations. 2. Please see "readme.scale" for calibration scale used for in-situ measuremnets from AGAGE GC-MS Medusa instruments. The calibration scale and unit of archived compounds can also be found in header lines of data files. 3. Most of GC-MS-Medusa data up to September 2011 are included in this update 4. 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 5. HFC-227ea, HFC-236fa and HFC-245fa data are included as part of released compounds measured by AGAGE GCMS-Medusa instrument in July 2011. The following 26 compounds are available from AGAGE GC-MS Medusa instrument for public access CFC-113 HCFC-22, HCFC-141b, HCFC-142b HFC-125, HFC-134a, HFC-152a, HFC-365mfc, HFC-23 Halon-1211, Halon-1301 CH3Cl, CH2Cl2, CHCl3, CH3Br CH3CCl3, CHClCCl2, CCl2CCl2 SF6, SO2F2 PFC-14, PFC-116, PFC-218 HFC-227ea HFC-236fa HFC-245fa 6. Please be aware both Medusa TCE (CHClCCl2), and PCE (CCl2CCl2) data have not been applied "blank correction". Those data are preliminary and will be updated later (after blank correction is applied). 7. It was found that there are offsets in Mace Head CHCl3 data between GC-MD and GC-MS Medusa measurements. The reason is unknown and it's under investigation by instrument team. ======= In subdirectories "complete" and "precisions", there are five further subdirectories (macehead, trinidad, barbados, samoa, tasmania), one for each monitoring site. The data files are named according to the convention station_name-medusa_yyyy.typ (example, MHD-medusa_2005.dat, and MHD-medusa_2005.pre) where "station_name" indicates station name, such as MHD -- Macehead THD -- Trinidadhead RPB -- Barbados SMO -- Samoa CGO -- Capegrim JFJ -- Jungfraujoch ZEP -- Zeppelin (Ny-Alesund), data are not available yet "medusa" indicates intrument (GC-MS-Medusa) "yyyy" inducates year (e.g. 2005) "typ" indicates date type, such as dat -- for measured compounds in mole fraction pre -- for precision information of measured species I. For measured compounds in mole fraction, for example, "Macehead_medusa_2009.dat" The first 6 lines are headers, 1st line, indicating the date of raw data file being created 2nd line, insturment type and statoin information 3rd line, data format 4th line, scale information of measured compounds 5th line, unit of measured compounds 6th line, lable of each column the first column, "time", is measurment time in fraction of year the 2nd column, "DD", is day number of measurement the 3rd column, "MM", is month of measurement the 4th column, "YYYY", is year of measurement The 5th column, "hh", is time in hour (0 to 23) The 6th column, "mm", is time in minute the 7th column, "ABSDA", is the day number since the first day of ALE/GAGE/AGAGE program from 8th to the last columns, are mole fractions (ppt) of measured species. a flag "P" immediately following reported mole fraction indicates it's a pollution event (non-baseline) base on AGAGE's pollution identification algorithm. For those without "P" flag, they are determined to be baseline data. II. For instrument precisions, for example, "MHD-medusa_2009.pre" It was represented by daily standard deviation of individual calibration tank measurements divided by the mean of two surrounding (in time) measurements (time 100; units are in percent). the 1st column, "time", indicates time in fraction of year the 2nd column, "DD" , indicates day the 3dd column, "MM", indicates month the 4th column, "YYYY", indicates year (YYYY) the 5th column, "Gday" is the day number since the first day of ALE/GAGE/AGAGE program For each compound, there are 2 columns used to indicate precisioninformation the 1st under "%s" column, is daily standard deviation in percent of the ratio of measured calibration tank values (as described earlier). In general, the smaller this number the better instrument precision. the 2nd column, under "n", indicates # of measurements to derive standard deviation ===== In sub-directory, "monthly", monthly average of background (i.e. without "P" flag) values at each site are saved here. In monthly mean file (e.g. "MHD-medusa.mon"), the first 6 lines are headers, followed by data columns the 1st column, "time", indicates time in fraction of year the 2nd column, "MM", indicates month the 3rd column, "YYYY", indicates year (YYYY) the next 3 columns (4th to 6th) are used to represent HFC-134a (first compound) where, "numb" indictes # of baseline measurements "HFC-134a" indicates monthly mean value of baseline data "std." indicates standard deviation of monthly mean The same format as columns (4th to 6th) is then repreated for all other reported species ==== END