GU0805-Leg 1 Pelagic Trawl Readme

Class of Data:  Surface ocean carbon dioxide concentrations

Dataset Identifer:  GU0805 Leg 1 Pelagic Trawl

Expocode:  33GG20081014

Statement of how to cite dataset:

     Gordon Gunter website: http://www.aoml.noaa.gov/ocd/gcc/rvgunter_introduction.php

     For more information on dataset citation and for a full description of the  
     instrumentation and procedures, see the Master Readme file accessible
     thru the Master Readme link located in the left navigation bar of the
     R/V Gordon Gunter web pages.
 
Measurement platform identifier:  R/V Gordon Gunter

Data quality issues:

     The data reduction for this dataset was done using the Matlab Reduction
     Program version 1.03.

     The standard gas tanks were not opened until 10/14/2008 at about 21:00
     (JDay 288).  After that time, tanks were opened but Std1 was taken out
     of the measurement sequence since it was empty.  It was later realized 
     that STD4 regulator had failed and the gas was not flowing.  The xCO2
     has been re-calculated using the calibration coefficients of the analyzer,
     the mV readings for CO2 and H2O, and the cell temperature and pressure. 

     Since only 2 Standards were good enough to correct the xCO2 values,
     all of them have been flagged 3 – 'corrected with less than 3 standards'.

     There were 3 areas where the TSG output constant values. These were
     flagged ‘Questionable SSS’.

     The fCO2 values reported are calculated at SST using the Sea Temperature
     data obtained from the ship. A delay of 3.34 min was applied to the SST data
     as determined in GU0805_Leg3 cruise data.
    
     
     Standard Gases and Reference Gas:  The three standard gases come from Scott-Marrin, Inc.,
     and are calibrated with primary standards that are directly traceable to the WMO scale.  
     The zero gas is a non-calibrated ultra-high purity gas from a commercial company.  Any 
     value outside the range of the standards should be considered approximate (5 ppm).
     While individual data points above 450 or below 245 may be less accurate, the general 
     trends should be indicative of the seawater chemistry.  
     The standards used on the cruise are:

           STANDARD          TANK #       CONCENTRATION       VENDOR
           STD1                               0.00         Commercial
           STD2              ja 2280          248.73       Scott-Marrin, Inc.
           STD3              ja 2292          372.88       Scott-Marrin, Inc.  
           STD4                               450.59       Scott-Marrin, Inc.                                              

                                         
     All xCO2 values are reported in parts per million (ppm) and fCO2
     values are reported in microatmospheres (uatm) assuming 100% humidity
     at the equilibrator temperature.

Ship Information:

     NOAA Research Vessel Gordon Gunter website:  http://www.moc.noaa.gov/gu/index.html

Scientists responsible for technical quality of this dataset:

     Rik Wanninkhof
     (305)361-4379
     Rik.Wanninkhof@noaa.gov 

     Denis Pierrot
     (305)361-4441
     Denis.Pierrot@noaa.gov

Timestamp for dataset reduction:  2/12/09

Timestamp for most recent update of dataset:  3/31/09

Time period the dataset refers to:  10/14/2008 - 10/24/2008

Geographic area the dataset refers to:

     Gulf of Mexico