1996 pCO2 intercomparison

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Workshop on Ocean Surface pCO2, Data Integration and Database Development, Jan 14-17, 2004, NIES, Tsukuba/Japan

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Cruise track of R/V Meteor cruise 36-1 from Hamilton, Bermuda to Las Palmas, Gran Canaria, Spain. Workshop on Ocean Surface pCO2, Data Integration and Database Development, Jan 14-17, 2004, NIES, Tsukuba/Japan

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Temperature and salinity range encountered during the course of the experiment. Workshop on Ocean Surface pCO2, Data Integration and Database Development, Jan 14-17, 2004, NIES, Tsukuba/Japan

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Schematic diagram of the underway pumping system for use in the “moon pool” of research vessels as used during the intercomparison exercise. All underway systems were connected to this system. Workshop on Ocean Surface pCO2, Data Integration and Database Development, Jan 14-17, 2004, NIES, Tsukuba/Japan

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Workshop on Ocean Surface pCO2, Data Integration and Database Development, Jan 14-17, 2004, NIES, Tsukuba/Japan Laboratory setup of the intercomparison exercise during Meteor cruise 36-1

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Workshop on Ocean Surface pCO2, Data Integration and Database Development, Jan 14-17, 2004, NIES, Tsukuba/Japan

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CSIRO MRI IFM UEA WHOI OU Workshop on Ocean Surface pCO2, Data Integration and Database Development, Jan 14-17, 2004, NIES, Tsukuba/Japan

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Test of CO2 calibration performance: Shown are the observed deviations from the concentrations of all measured NOAA/CMDL CO2 standards. Pink crosses indicate the concentrations of the standards used in the exercise. The legend gives details of the nominal concentrations used for calibration. Also shown is the range of measured xCO2 during the whole intercomparison. Workshop on Ocean Surface pCO2, Data Integration and Database Development, Jan 14-17, 2004, NIES, Tsukuba/Japan

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Test of equilibrator temperature probes: Shown are the deviations of the measured temperatures from the reference temperature. Equilibrator probe and reference probe were kept together in the same water bath until readings became stable. Also shown are the linear correction lines which were applied to temperature readings of that particular system. Workshop on Ocean Surface pCO2, Data Integration and Database Development, Jan 14-17, 2004, NIES, Tsukuba/Japan

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Comparison of measured CO2 mole fraction in dry air (xCO2air): The black horizontal lines represent the overall mean xCO2air value (± 1 s.d.) calculated from systems “B”–“E”. Workshop on Ocean Surface pCO2, Data Integration and Database Development, Jan 14-17, 2004, NIES, Tsukuba/Japan

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Mean values of the CO2 mole fraction in dry air (xCO2air) as measured by laboratories “A”–“E” and “G” during the period of the intercomparison exercise where data from all six systems are available (June 7, 22:30 UTC to June 13, 12:30 UTC). Also shown is the standard deviation of all xCO2air data sets from their mean. The horizontal line represents the mean xCO2air value calculated from the means of profiles “B”–“E” for this limited period of time. Workshop on Ocean Surface pCO2, Data Integration and Database Development, Jan 14-17, 2004, NIES, Tsukuba/Japan

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Table 3. Daily mean (± standard deviation) of deviations from the 11-min running mean of “D” and “E” (reference). Deviations exceeding ± 2 µatm are marked in bold. Smaller deviations are not significant under the technical circumstances of this exercise. The results for “D” and “E” are shown in italics to indicate that this data have been used to calculate the reference. Workshop on Ocean Surface pCO2, Data Integration and Database Development, Jan 14-17, 2004, NIES, Tsukuba/Japan

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Workshop on Ocean Surface pCO2, Data Integration and Database Development, Jan 14-17, 2004, NIES, Tsukuba/Japan Typical picture from second half of the cruise where little variability in SST and SSS prevailed.

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Workshop on Ocean Surface pCO2, Data Integration and Database Development, Jan 14-17, 2004, NIES, Tsukuba/Japan Typical picture from second half of the cruise where little variability in SST and SSS prevailed.

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Workshop on Ocean Surface pCO2, Data Integration and Database Development, Jan 14-17, 2004, NIES, Tsukuba/Japan

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Workshop on Ocean Surface pCO2, Data Integration and Database Development, Jan 14-17, 2004, NIES, Tsukuba/Japan Summary Equilibrator design: with regard to the achievable accuracy no „best choice“ can be identified. Different design, however, has consequences for the equilibration time constant. Also, higher water flow rates generally lead to a smaller warming effect. Wet air NDIR measurements (using the LI-COR 6252) may be characterized by some loss in accuracy although this does not seem to be a major problem. The factory-calibration of the LI-COR instruments (“zero” and “span” adjustment of the factory-polynomial) does not achieve the necessary accuracy. Thermostatting the sample air flow prior to the NDIR measurement is recommended. Temperature measurements are not always done with the necessary care and appear to introduce large errors (up to 7 µatm during this exercise). Seawater pCO2 measurements can be made to a high degree of agreement (± 1 µatm). However, even apparently well-functioning system can disagree by several µatm

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Workshop on Ocean Surface pCO2, Data Integration and Database Development, Jan 14-17, 2004, NIES, Tsukuba/Japan

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Workshop on Ocean Surface pCO2, Data Integration and Database Development, Jan 14-17, 2004, NIES, Tsukuba/Japan