# file: itn_CCl4_All.dat # # Atmospheric measurements of CCl4 (Carbon Tetrachloride, CT) # # Measurements are from the NOAA/ESRL/GMD/HATS flask program # (http://www.esrl.noaa.gov/gmd/hats/flask/flasks.html). # Instrument ID: Otto # # Location: ITN -- Grifton, North Carolina -- 35.37 N, 77.39 W, 8 m Elev. # See http://www.esrl.noaa.gov/gmd/dv/site/site_table.html#hats_flask for # more information about flask sampling sites. # # The data reported are from samples collected approximately once per week in # matching, concurrent, flask pairs and later analyzed on a gas chromatograph # with electron capture detection (GC-ECD) located in Boulder, Colorado, USA. # This system uses two standard reference gases for calibration and has been # in operation since very early in 1995. # # CCl4 loss during storage in stainless-steel canisters arises most commonly at # high-latitude and/or high-altitude sites where the air is dry (i.e. ALT, BRW, # MLO, NWR, and SPO -- especially in winter). Extra efforts have been made to # flag samples suspected of suffering from this known artifact, thereby barring # them from inclusion in monthly mean estimates. The user is cautioned, # however, that small biases to the low side may nevertheless remain. # # These data represent mean estimates from pairs of concurrently-collected # flask samples based on several injections from each flask. Mean estimates # are derived for each individual flask, then the flask estimates are combined # into a single estimate for the pair. Ideally, each concentration is estimated # three different ways using three simple calibration curves. A two-point # calibration is derived from nearby responses to both reference gases # considered in unison, and separate one-point calibrations are derived from # nearby responses to each reference gas considered in isolation from the # other. These estimates are then reconciled in accordance with the method # outlined at # # ftp://aftp.cmdl.noaa.gov/data/hats/doc/HATSflaskECDanalysis.docx # # A series of seven binary QC flag fields is included with each entry. In order # from left to right, a 1 signifies that 1) a single reference gas was used for # calibration, 2) one or more sample injections occurred at subambient flask # pressure (raising the risk of contamination), 3) the precision of the # estimate is worse than 2.5% of the mean, 4) the estimate has been flagged -- # either by a loess-based statistical outlier algorithm, or, on occasion, # selectively -- as "suspect", 5) the estimate is based on a single flask # sample with a missing paired partner, 6) the estimates from the individual # flask partners disagree by more than twice their summed precisions. The # seventh and final flag is turned on whenever one of flags 4, 5 or 6 is # thrown. This is to conveniently mark samples that are excluded from the # computation of monthly mean values presented in the companion file named # "itn_CCl4_MM.dat". Flags 1, 2 and 3 are considered purely descriptive in # nature, serving only to raise suspicion of a sample. Flag 4 promotes any # suspicion to exclusionary status. The algorithm used for setting flag 4 is # applied only to baseline (i.e. coastal, high-altitude, or otherwise remote) # sites. Samples from continental sites known to have nearby urban influences # (e.g. HFM, ITN, and LEF) are flagged as suspect only when obvious # chromatography issues were present during the analysis. This elevates the # risk of sample over-exclusion (i.e. false positives occurring in flag 4 and # hence also in flag 7) among the baseline sites, while for the continental, # urban-influenced sites there is a greater risk of sample under-exclusion. # # PIs: Dr. James W. Elkins, Dr. Bradley D. Hall, # Debra J. Mondeel, J. David Nance # # National Oceanic and Atmospheric Administration (NOAA) # Earth System Research Laboratory (ESRL) # 325 Broadway, R/GMD1 # Boulder, CO 80305-3328 # # Email: James.W.Elkins@noaa.gov; Bradley.Hall@noaa.gov # Phone: (303) 497-6224 (303) 497-7011 # # Email: Debra.J.Mondeel@noaa.gov; David.Nance@noaa.gov # Phone: (303) 497-6013 (303) 497-7002 # # Fax: (303) 497-6290 # # Data use policy: # If you use this data in a publication or report, we would appreciate that you # contact the principal investigators (PIs) first and discuss your interests. # The PIs can discuss the quality of the data and any potential problems with # its analysis. Please contact the PIs for more information. The data should # be cited in presentations or publications along the following lines: Carbon Tetrachloride # data from the NOAA/ESRL halocarbons flask program. # # Calibration scale: NOAA 2008 # See http://www.esrl.noaa.gov/gmd/ccl/scales.html for more information about # calibration scales. # # Units: ppt # # Missing value: "nan" # # Data Columns: # yr Year # mon Month # day Day of the Month # hour Hour of the Day # min Minute of the Hour # m Mean flask-pair concentration of CCl4 in ppt # sd Standard deviation # pid Flask-pair ID # ftype Type of flasks in pair # U: unknown # S: stainless steel # G: glass # B: both (i.e. one of each) # flag1 0: normal (this also applies to all flags that follow) # 1: a single reference gas was used for calibration # flag2 1: one or more sample injections occurred at subambient pressure # flag3 1: precision > 2.5% of estimated concentration # flag4 1: marked suspect by a loess-based statistical outlier algorithm # flag5 1: single flask with missing paired partner # flag6 1: paired partners disagree by more than twice their summed # precisions # flag7 1: sample excluded from monthly mean computations ("itn_CCl4_MM.dat") # CCl4ottoITNyr CCl4ottoITNmon CCl4ottoITNday CCl4ottoITNhour CCl4ottoITNmin CCl4ottoITNm CCl4ottoITNsd CCl4ottoITNpid CCl4ottoITNftype CCl4ottoITNflag1 CCl4ottoITNflag2 CCl4ottoITNflag3 CCl4ottoITNflag4 CCl4ottoITNflag5 CCl4ottoITNflag6 CCl4ottoITNflag7 1995 08 16 16 19 100.180 2.195 00239 S 0 0 0 1 0 0 1 1995 09 20 15 59 104.996 0.721 00269 S 0 0 0 1 0 0 1 1995 10 25 15 00 104.094 0.509 00295 S 0 0 0 1 0 0 1 1995 11 22 16 12 103.123 0.336 00344 S 0 0 0 1 0 0 1 1996 01 03 18 17 105.581 0.690 00372 S 0 0 0 0 0 0 0 1996 01 17 17 50 107.082 0.473 00384 S 0 0 0 0 0 0 0 1996 02 21 16 19 105.579 0.763 00413 S 0 0 0 0 0 0 0 1996 03 27 15 25 105.259 0.317 00451 S 0 0 0 0 1 0 1 1996 04 10 14 35 105.211 0.438 00462 S 0 0 0 0 0 0 0 1996 05 01 15 14 105.159 0.420 00478 S 0 0 0 0 0 0 0 1996 05 15 16 44 105.571 0.473 00494 S 0 0 0 0 0 0 0 1996 05 29 16 55 105.284 0.367 00502 S 0 0 0 0 0 0 0 1996 06 12 17 15 105.028 0.378 00521 S 0 0 0 0 0 0 0 1996 06 26 16 25 105.616 0.227 00537 S 0 0 0 0 0 0 0 1996 07 10 16 25 105.930 0.422 00552 S 0 0 0 0 0 0 0 1996 07 24 15 55 106.122 0.391 00563 S 0 0 0 0 0 0 0 1996 08 07 16 25 105.896 0.388 00567 S 0 0 0 0 0 0 0 1996 08 21 15 30 105.863 0.411 00592 S 0 0 0 0 0 0 0 1996 09 04 15 30 105.031 0.429 00606 S 0 0 0 0 0 0 0 1996 09 18 15 50 105.287 0.829 00618 S 0 0 0 0 0 0 0 1996 10 23 16 25 105.829 0.881 00648 S 0 0 0 0 0 0 0 1996 11 06 17 14 107.102 0.559 00658 S 0 0 0 0 0 0 0 1996 11 27 16 54 105.401 0.448 00689 S 0 0 0 0 0 0 0 1996 12 11 16 44 106.436 0.726 00698 S 0 0 0 0 0 0 0 1997 01 02 16 55 104.922 0.626 00728 S 0 0 0 0 0 0 0 1997 01 22 16 44 107.424 0.444 00738 S 0 0 0 0 0 0 0 1997 02 05 16 25 107.032 0.410 00759 S 0 0 0 0 0 0 0 1997 02 19 16 15 106.395 0.276 00770 S 0 0 0 0 0 0 0 1997 03 26 17 15 104.421 0.265 00802 S 0 0 0 0 0 0 0 1997 04 09 16 50 103.749 0.385 00815 S 0 0 0 0 0 0 0 1997 04 23 15 24 106.915 0.308 00822 S 0 0 0 0 0 0 0 1997 07 02 16 20 104.658 0.379 00884 S 0 0 0 0 0 0 0 1997 07 16 16 25 106.253 0.295 00897 S 0 0 0 0 0 0 0 1997 08 13 16 04 104.717 0.340 00935 S 0 0 0 0 0 0 0 1997 08 27 16 09 105.091 0.363 00940 S 0 0 0 0 0 0 0 1997 09 17 16 44 106.419 0.482 00954 S 0 0 0 0 0 0 0 1997 10 08 15 49 105.278 0.414 00971 S 0 0 0 0 0 0 0 1997 10 29 16 34 104.011 0.798 00984 S 0 0 0 0 0 1 1 1997 11 19 16 40 104.461 0.376 01005 S 0 0 0 0 0 0 0 1997 12 10 16 55 104.688 0.337 01047 S 0 0 0 0 0 0 0 1998 01 07 17 00 103.640 0.340 01061 S 0 0 0 0 0 0 0 1998 01 28 16 49 103.522 0.687 01079 S 0 0 0 0 0 0 0 1998 02 18 16 44 103.737 0.441 01103 S 0 0 0 0 0 0 0 1998 03 11 17 15 99.257 2.915 01118 S 0 0 1 0 0 1 1 1998 04 01 16 55 104.129 0.325 01136 S 0 0 0 0 0 0 0 1998 04 15 14 49 104.264 0.302 01153 S 0 0 0 0 0 0 0 1998 05 27 15 44 104.822 0.296 01191 S 0 0 0 0 0 0 0 1998 06 24 15 19 103.070 0.369 01221 S 0 0 0 0 0 0 0 1998 07 01 15 45 103.710 0.209 01224 S 0 0 0 0 0 0 0 1998 08 19 15 44 104.726 0.409 01284 S 0 0 0 0 0 0 0 1998 09 15 16 14 98.457 1.766 01308 S 0 0 0 1 0 0 1 1998 10 07 16 05 106.211 0.672 01334 S 0 0 0 0 0 0 0 1998 10 28 16 40 104.361 0.546 01358 S 0 0 0 0 0 0 0 1998 11 25 15 14 103.710 0.264 01397 S 0 0 0 0 0 0 0 1998 12 09 17 15 102.663 1.903 01428 S 0 0 0 0 0 0 0 1998 12 30 16 55 102.348 0.326 01436 S 0 0 0 0 0 0 0 1999 01 27 15 20 102.951 0.463 01459 S 0 0 0 0 0 0 0 1999 02 10 16 34 102.645 0.949 01483 S 0 0 0 0 0 1 1 1999 03 03 16 24 103.949 0.345 01522 S 0 0 0 0 0 0 0 1999 03 24 15 59 104.220 0.556 01529 S 0 0 0 0 0 0 0 1999 04 21 15 25 102.992 0.202 01553 S 0 0 0 0 0 0 0 1999 05 05 15 05 103.090 0.476 01575 S 0 0 0 0 0 0 0 1999 05 12 15 34 102.391 0.227 01587 S 0 0 0 0 0 0 0 1999 05 26 14 34 101.688 0.295 01599 S 0 0 0 0 0 0 0 1999 06 02 15 19 103.205 0.258 01608 S 0 0 0 0 0 0 0 1999 06 09 14 39 112.350 0.310 01618 S 0 0 0 1 0 0 1