ORNL/CDIAC-103
                                                     NDP-064
                                
                                
     SURFACE WATER AND ATMOSPHERIC UNDERWAY CARBON DATA OBTAINED
     DURING THE WORLD OCEAN CIRCULATION EXPERIMENT INDIAN OCEAN
     SURVEY CRUISES (R/V KNORR, DECEMBER 1994 JANUARY 1996)
                                
                         Contributed by
             Christopher L. Sabine and Robert M. Key
         Department of Geosciences, Princeton University
                      Princeton, New Jersey
                                
                          Prepared by 
               Alexander Kozyr1 and Linda Allison
           Carbon Dioxide Information Analysis Center
                  Oak Ridge National Laboratory
                      Oak Ridge, Tennessee
                                
           1Energy, Environment, and Resources Center
                   The University of Tennessee
                      Knoxville, Tennessee
                                
                 Environmental Sciences Division
                      Publication No. 4701
                                
                 Date Published:  November 1997
                                
                        Prepared for the
                 Environmental Sciences Division
         Office of Biological and Environmental Research
                    U.S. Department of Energy
      Budget Activity Numbers KP 12 04 01 0 and KP 12 02 03 0
                                
                         Prepared by the
           Carbon Dioxide Information Analysis Center
                  OAK RIDGE NATIONAL LABORATORY
                 Oak Ridge, Tennessee 37831-6335
                           managed by
              LOCKHEED MARTIN ENERGY RESEARCH CORP.
                             for the
                    U.S. DEPARTMENT OF ENERGY
                   under contract DE-AC05-96OR22464                                                                        




                ABSTRACT
                                
Sabine, C. L., and R. M. Key.  1997.  Surface Water and Atmospheric 
  Underway Carbon  Data Obtained During the World Ocean Circulation 
  Experiment Indian Ocean Survey Cruises (R/V Knorr, December 1994 - 
  January 1996).  ORNL/CDIAC-103, NDP-064. Carbon Dioxide Information 
  Analysis Center, Oak Ridge National Laboratory, U.S. Department of 
  Energy, Oak Ridge, Tennessee.
     
                                                            
This data documentation presents the results of the surface water and 
atmospheric underway measurements of mole fraction of carbon dioxide (xCO2), 
sea surface salinity, and sea surface temperature, obtained during the World 
Ocean Circulation Experiment (WOCE) Indian Ocean survey cruises 
(December 1994 - January 1996).  Discrete and underway carbon measurements
were made by members of the CO2 survey team.  The survey team is a part of 
the Joint Global Ocean Flux Study supported by the U.S. Department of Energy 
to make carbon-related measurements on the WOCE global survey cruises.
                                                            
Approximately 200,000 surface seawater and 50,000 marine air xCO2 measurements
were recorded.  Seawater values ranged from 310 ppm to greater than 610 ppm.
The lowest values (~50 ppm below atmospheric) were measured in the southwestern 
Indian Ocean, south of Madagascar.  The highest values (more than 250 ppm higher
than atmospheric) were found in the Arabian Sea associated with the southwest 
monsoon upwelling.
                                                            
All measurements were made using the new fully automated system, designed by 
the scientists of the Princeton University Ocean Tracers Laboratory.  This 
system was continuously running during all nine Indian Ocean cruises aboard 
Research Vessel Knorr.  The system (fully described in Appendix A of printed 
documentation) had a response time of ~1 min and a long-term precision and 
accuracy of ~0.4 and 1 ppm, respectively.  The equilibrator design is a 
modification of a counterflow disk stripper that has been used in the past to
extract soluble gases from seawater.  The detector is a dual-beam infrared 
spectrometer.  Calibration and operation of the instrument as well as data 
logging are computer controlled and require minimal attention.  The design is 
such that other instrumentation can be easily added.  Details of the 
instrument control, calibration, and efficiency tests for this instrument are 
given to assist others interested in building similar-type systems.
                                                            
The Indian Ocean underway CO2 data set is available free of charge as a numeric 
data package (NDP) from the Carbon Dioxide Information Analysis Center.  The NDP
consists of twenty data files, two FORTRAN 77 routines, a readme file, and this 
printed documentation.  The data files and html version of this report can be 
accessed through the following World Wide Web site: 
http://cdiac.esd.ornl.gov/oceans/doc.html.
     
     
     Keywords: carbon cycle; carbonate chemistry; underway measurements



     
                           PART 1:
     
                          OVERVIEW



                      1. INTRODUCTION
                                
                                                            
January 1996 marked the completion of a 14-month, 92,000 km-long hydrographic survey of
the Indian Ocean by the World Ocean Circulation Experiment (WOCE) Hydrographic Programme
(WHP).  In addition to the standard WOCE hydrographic parameters measured on these
cruises, discrete and underway carbon measurements were made by members of the carbon
dioxide (CO2) survey team.  The survey team is a part of the Joint Global Ocean Flux Study
(JGOFS) supported by the U.S. Department of Energy (DOE) to make carbon system
measurements on the WOCE global survey cruises.  As part of the survey team, the Princeton
University (PU) Ocean Tracers Laboratory (OTL) constructed an automated system for underway
analysis of surface water and marine air CO2 concentrations (hereafter referred to as the underway
system).  With the help of the other science team members, the underway system was run aboard
Research Vessel (R/V) Knorr during all nine legs of the Indian Ocean survey.  All measured data
and documentation are available to the public through the Carbon Dioxide Information Analysis
Center (CDIAC).  This report provides a description of the data files, underway system as well
as a brief explanation of when and where the data were collected, any problems encountered with
the system, and how the data can be accessed through CDIAC.
                                                            
The underway system was installed by R. M. Key of Princeton University on the R/V Knorr
in November 1994, prior to the first leg of the survey.  Table 1 lists the chief scientist, cruise
dates, ports of call, affiliation of the group responsible for discrete carbon sampling, and the analyst
in charge of operating the underway system for each of the Indian Ocean legs.  On all legs except
the first, the CO2 analyst responsible for operating the underway system was a member of the
OTL group.
                                                            
A majority of the data are of excellent quality.  The only major technical problems were
encountered on the first leg as a result of failures in the ship's seawater supply system. 
Approximately 10 days after the R/V Knorr departed Fremantle, Australia, for the first leg of the
survey, the ship encountered heavy weather that resulted in frequent shutdowns of the ship's
uncontaminated seawater pump.  On December 19, 1994, the seawater supply for the underway
system was switched to a secondary seawater pump.  Post-cruise examination of the data revealed
that the water from this pump had undergone significant heating, presumably the result of a long
(and apparently variable) residence time in the ship.  The underway temperature and salinity
values recorded during this time are also questionable because they do not track very well with
the surface temperature and salinity measured by a conductivity, temperature, and depth sensor
(CTD).  After careful analysis, much of the data had to be flagged as bad, and the remaining data
are much "noisier" than data from subsequent legs.  The original uncontaminated seawater supply
was back on-line for the second leg and operated with only minor outages for the remainder of
the survey.  By the end of the survey on January 22, 1996, nearly 250,000 individual
measurements of surface water and atmospheric mole fraction of CO2 (xCO2) were recorded. 
Seawater values ranged from 310 ppm to greater than 610 ppm.  The lowest values (~50 ppm
below atmospheric) were measured in the southwestern Indian Ocean, south of Madagascar.  The
highest values (more than 250 ppm higher than atmospheric) were found in the Arabian Sea and
were associated with the southwest monsoon upwelling.
                                                            
This report provides details on the calibration and quality control procedures followed in the
production of this data set.  An extensive account of specific events potentially affecting the CO2
underway system has been compiled from the original notebooks and is included in Appendix B of 
printed documentation. The major events are briefly described in the Results section, but a number 
of minor events (e.g., times when the drying column was changed), which did not appear to have a 
direct effect on the results, are only recorded in the Appendix B.  For further details on additional measured parameters and the objectives of each leg see the individual WOCE cruise reports produced by
the chief scientist (http://www.cms.udel.edu/woce/dacs/whp_dac_one.html).
     
     
     Table 1.  Information on individual legs of WOCE Indian Ocean Survey
                                 
------------------------------------------------------------------------------------------------
WOCE         Chief         Cruise dates         Ports of call             Carbon   Underway
section    scientist                                                       group  system analyst
------------------------------------------------------------------------------------------------
     
I8S/I9S  M. McCartney   12/01/94-01/19/95  Fremantle, AU-Fremantle, AU	    BNL   K. Johnson
     
I9N      A. Gordon      01/24/95-03/06/95  Fremantle, AU-Colombo, Sri Lanka  PU   C. Sabine
     
I8N/I5E  L. Talley      03/10/95-04/06/95  Colombo, Sri Lanka-Fremantle, AU  UH   G. McDonald
     
I3       W. Nowlin      04/23/95-06/05/95  Fremantle, AU-Mauritius           UM   R. Key
     
I5W/I4   J. Toole       06/11/95-07/11/95  Mauritius-Mauritius              BNL   T. Key
     
I7N      D. Olson       07/15/95-08/24/95  Mauritius-Muscat, Oman            UH   T. Zahn
     
I1       J. Morrison    08/29/95-10/16/95  Muscat, Oman-Singapore          WHOI   R. Rotter
     
I10      N. Bray        11/11/95-11/28/95  Dampier, AU-Singapore             PU   T. Key
     
I2       G. Johnson     12/02/95-01/22/96  Singapore-Mombasa, Kenya          UH   A. Dorety
     
     
 BNL - Brookhaven National Laboratory;                       
  PU - Princeton University;                                 
  UH - University of Hawaii;
  UM - University of Miami;
WHOI - Woods Hole Oceanographic Institution.
     
     
              2. MEASUREMENTS, INSTRUMENTATION, AND CALIBRATIONS
                                 
                         
The Princeton underway system was designed and constructed by OTL personnel for
automated, high-resolution surface water and atmospheric boundary layer CO2 concentration
measurements.  The system is controlled by a personal computer that is programmed to perform
periodic calibrations, determine detector stability, and alternately measure the seawater and marine
air CO2 concentrations.  A dual-beam infrared spectrometer (Li-Cor 6251) is used to measure the
CO2 concentration in the gas stream.  The input gas to the detector (either one of four calibrated
standards, air-equilibrated with surface seawater or marine air) is selected with an electronic 6-port
valve.  Prior to entering the detector, the gas is passed through a hygroscopic ion-exchange
membrane (Nafion) and a small magnesium perchlorate/AquasorbTM column to remove water
vapor.  Marine air is pumped from the bow or stern of the research vessel to avoid contamination
from the ship's exhaust.  The surface water CO2 concentration is determined by continuously
pumping seawater from the ship's intake (depth ~7m) through the counterflow disk equilibrator. 
The equilibrator design is a modification of a disk stripper that has been shown to be very
efficient at extracting soluble gases from seawater.  Water flows through the bottom half of the
chamber at a rate of approximately 18 L/min and is then dumped overboard.  A fixed volume of
air is recirculated through the top half of the chamber in the opposite direction as the water flow. 
Sixty disks are mounted on a stainless steel shaft that runs along the axis of the chamber.  The
disks are rotated at 135 rpm so they can pick up a thin film of water on either side, greatly
increasing the surface area of the water.  Thus, the chamber equilibrates a very large volume of
water with a small fixed volume (~6 L) of air.  With the rotating disks, the equilibrator's response
to an instantaneous change in the CO2 of the water is an exponential mixing function.  Laboratory
and "at sea" tests indicate that the response time for this system was approximately 1 minute.  The
precision of the  measurements, estimated from times when the ship was not moving and multiple
measurements were made at the same location, was estimated to be approximately 0.4 ppm.  This
is comparable to the precision obtained from standard gas and marine air measurements.  The
average water and air sampling frequencies for the Indian Ocean legs were ~2.5 and 9.5 min,
respectively.  Comparison of these measurements with those from an independent underway
system operated by R. Weiss of Scripps Institution of Oceanography (SIO) on the same vessel
agreed to better than 1 ppm (R. Weiss, personal communication, 1995).  Further details of the
underway system design and operation can be found in Sabine and Key, 1996, which is reprinted
in Appendix A of printed documentation.
                         
The infrared detector used during the Indian Ocean survey cruises had an instrumental drift
that could be significant on the timescale of a day.  The primary calibration method for this
system, therefore, was the periodic analysis of gas standards having known CO2 concentrations. 
A detailed description of the philosophies and mechanics of how the detector readings were
calibrated is given in Appendix A of printed documentation.  In addition to the accuracy of 
the CO2 standard gases, the accuracy of the final results at in situ conditions depends on 
supporting measurements of temperature, pressure, and salinity.  This section discusses the 
calibration of relevant parameters given in this report.
     
     
     2.1  CO2 Standard Gases
     
                         
The data collection program for the Indian Ocean survey cruises was set up to record five
readings from each of the four calibration gases (the reference and three CO2 standard gases) every
three hours.  All of the gases were a mixture of CO2 in artificial air (oxygen, nitrogen, and argon
in atmospheric ratios) prepared by Scott Specialty Gases, Inc.  The nominal CO2 concentrations
for the three standard gases were 280, 360, and 450 ppm respectively.  A reference gas with a
nominal concentration of 200 ppm was used on almost all of the cruises to increase the dynamic
range of the detector output.  Five tanks of calibrated reference gas were put aboard the R/V Knorr 
before the first leg of the survey.  However, these tanks were exhausted before a resupply container 
could be sent with additional calibrated gases.  After the first two weeks of leg I7N the reference 
gas was switched to a CO2-free air tank.  Additional gas tanks were delivered to the ship between 
legs I1 and I10, so the final two legs (legs I10 and I2) were again run with a 200 ppm reference gas.  
The exact times that the reference tanks were in use as well as the calibrated concentrations are given 
in Appendix B of printed documentation.  The flow rate on the three CO2 standards used for calibrations 
was sufficiently low to make one set of tanks last for the entire survey.
                         
All of the CO2 standards used for this survey were calibrated by R. Van Woy (SIO) using
a technique that employs a GC/FID with catalytic conversion to CH4 (Weiss 1981).  The GC
system was calibrated against C. D. Keeling-certified standards with concentrations of 213.14,
296.65, 349.97, and 458.06 ppm.  The CO2 standard gases and the initial five reference tanks were
calibrated in September 1994, prior to the first cruise.  The overall accuracy of the reported final
values was estimated to be 0.3 ppm.  After completion of the last leg of the survey, the three
standard gases were returned to R. Weiss' laboratory at SIO for post-cruise calibration in June
1996.  Table 2 summarizes the initial and final calibrations of these gases.  In all cases the post-
cruise calibration was within the estimated accuracy of the initial calibration.
     
     
          Table 2.  Calibrated values for CO2 standards
                                 
     -------------------------------------------------------------------------------
     Tank ID no.     Date of use    Legs covered       Pre-cruise        Post-cruise
                                                         (ppmv)              (ppmv)
     -------------------------------------------------------------------------------     
     ALM017714    11/27/94 01/22/96     All            456.37  0.21    455.69  0.15
     
     AAL9328      11/27/94 01/22/96     All            361.92  0.18    361.80  0.07
     
     ALM017544    11/27/94 01/22/96     All            284.39  0.18    284.07  0.09
     
     ALM17637     11/27/94 01/03/95   I8S/I9S          198.92  0.13    N/A
     
     AAL1791      01/03/95 02/09/95   I8S/I9S, I9N     199.55  0.14    N/A
     
     ALM008242    02/09/95 04/03/95   I9N, I8N/I5E     198.74  0.15    N/A
     
     ALM027282    04/03/95 05/24/95   I8N/I5E, I3      198.80  0.16    N/A
     
     ALM14400     05/24/95 07/25/95   I3, I5W/I4, I7N  198.63  0.11	N/A
     
     24813        07/25/95 08/15/95   I7N              0.00             N/A
     
     18260        08/15/95 10/13/95   I7N, I1          0.00             N/A
     
     ALM061635    11/01/95 12/29/95   I10, I2          200.88  0.15    N/A
     
     ALM45918     12/29/95 01/22/96   I2               200.92  0.15    N/A
     
     
     
     
     
     
     
     2.2 Underway Sea Surface Temperature, Salinity, and Position 
     
                         
Underway sea surface temperature and conductivity were measured using a Falmouth
Scientific thermosalinograph (OCM-TH-212) as part of the R/V Knorr improved meteorological
(IMET) sensor system.  Readings were averaged and recorded at one-minute time intervals
together with the global positioning system (GPS) time and location.  Underway salinity was
calculated relative to the 1978 practical salinity scale from the calibrated temperature and the raw
conductivity readings using the equations of Lewis (1980).  These data were quality controlled
by examining all of the points recorded in two-day intervals and outliers discarded based on visual
inspection.  Values were generally discarded when they were more than two standard deviations
away from a time local mean.  The exact value for the cut, therefore, depended on the
instrumental noise at the time.  Questionable points were generally left in the data set.  The
temperature, salinity, latitude, and longitude were then matched to the times when xCO2 data were
recorded.  Linear interpolation was used to fill in for values cut in the QC process. 
                         
Both the temperature and salinity values were calibrated against the WOCE preliminary
surface bottle values at each station.  Although the exact trip time is not generally recorded in the
WOCE ".SEA" files, the ".SUM" files do record the beginning and ending times of each cast.
Since the Niskin bottles were tripped on the upcast, the surface bottle was tripped immediately
before the rosette was brought aboard and the cast was completed.  The end time for the cast was,
therefore, taken as the trip time for the surface bottle at each station.  The surface station data
were then tied to the underway data by calculating the mean and median values of the underway
data for the 15 minutes prior to the recorded cast end time.  Although the ship was not underway
while the cast was in progress, there was the potential that differences between the underway
temperature readings and the discrete samples could have been real in very-high-gradient regions.
Stations where the mean and median values were greater than 0.01 units apart were, therefore,
flagged as questionable and not considered in the calibration fits.
                         
Since the salinity measurements are a function of temperature, the temperature calibration was
performed first.  As noted earlier, the temperature data from section I8S/I9S were considerably
noisier and appeared to have a different correlation with the CTD data than had data from the
other legs.  There were no significant differences among the remaining eight cruises, so they were
all fit with a single function.  Of the 1096 stations occupied after leg I8S/I9S, 201 were flagged
as questionable.  The remaining data were calibrated with a linear fit to the CTD temperature.
The fitted slope of 1.0013  0.0003 indicates that the sensor had a nearly ideal response.
The intercept of 0.095  0.007 indicates that the ship's sensor was reading nearly 0.1C high.  The
final calibrated underway temperature values were within 0.026C of the CTD values at the
stations.  The data from section I8S/I9S have a slightly different calibration function because the
pump with the thermosalinograph was shutdown early in the cruise.  Without a constant flow of
fresh water across the sensor, the response relied more on diffusion and turbulent mixing at the
intake.  For this cruise, the sensor slope was significantly different from 1 (1.068  0.007), and
the offset was 1.53  0.07C.  The standard deviation of the difference between the
I8S/I9S CTD surface temperatures and the calibrated underway temperatures estimated at 131
stations was 0.44C.
                         
Underway salinity was calibrated to the preliminary WOCE bottle salinity results.
Examination of the salinity data suggested that the calibration for the salinograph varied on a
timescale of approximately 1 month.  No obvious correlation was observed between the
variability and the in situ temperature or salinity.  On average, the uncalibrated underway salinity
values were approximately 1.3 lower than the bottle salinity values.  The reason for the varying 
offset is not known, but given this variability the underway data were fit to the station data for
each leg individually.
          
Table 3 lists the coefficients for each leg.  The problems with the pump shutdown on line
I8S/I9S had a much more drastic effect on salinity than on temperature.  The underway salinity
values on that cruise did not track the station salinity values and were, therefore, deemed
unreliable.  The salinity values given in the I8S/I9S data set are simply a linear interpolation of
the station data.  The thermosalinograph gave much better results on all of the legs after I8S/I9S. 
The standard deviation of the difference between the WOCE bottle salinities and the calibrated
underway salinity values at the stations occupied on legs I9N through I2 was 0.058. 
     
     Table 3.  Coefficients for linear calibration of underway salinity
                                 
     ---------------------------------------------------------------
     Leg       Intercept       Std. Dev.      Slope       Std. Dev.
     ---------------------------------------------------------------     
     I9N        +1.008           0.10         1.0091        0.003
     
     I8N/I5E    -0.459           0.09         1.0539        0.003
     
     I3         -0.335           0.25         1.0495        0.007
     
     I5W/I4     -2.830           0.56         1.1245        0.020
     
     I7N        +0.130           0.20         1.0368        0.007
     
     I1         -0.230           0.20         1.0518        0.006
     
     I10        -0.104           0.09         1.0382        0.003
     
     I2         -1.548           0.14         1.0863        0.004
     
     
     
     2.3 Underway CO2 System Parameters
     
          
The temperature of the water inside the equilibrator was monitored with a Rosemont
ultralinear platinum resistance thermometer (PRT).  The PRT was calibrated in March 1994, prior
to the first leg of the survey, by the SIO Ocean Data Facility (ODF) using standard CTD
calibration techniques.  Estimated accuracy was 0.003C on the ITS90 scale.  A secondary check
on the accuracy of the equilibrator temperature readings was made by frequently comparing
temperature readings from a mercury thermometer, located in the equilibrator, to values recorded
from the PRT.
          
Temperature readings from the Li-Cor detector were not explicitly calibrated for this survey
because the final results are only a function of the relative changes in temperature between the
standard gases and the sample.  
          
The sensor used to monitor the system pressure (Setra Systems Inc.) was factory-calibrated
prior to the survey in August 1994 against NIST-traceable primary standards.  Estimated accuracy
was 0.05%.
          
All system inputs were read into the computer as voltages using a National Instruments Lab-
PC+ A/D board.  Accuracy of the board's readings was confirmed with a Fluke model 8840A 
5-digit voltmeter prior to the survey.  The resolution of the readings was a function of the
voltage range being measured, but in all cases was at least an order of magnitude smaller than the
estimated precision of the measurement.
          
Data directly recorded by the underway system were tagged with a time based on the internal
clock of the PC running the instrument.  This clock was manually reset to Greenwich Mean Time
(GMT) at the beginning of each leg.  The IMET and navigation data recorded by the ship's
system were tagged with GMT recorded from the GPS satellite data.  A test of how closely the
data were in sync was performed on every leg by examining the time offset between the
observation of temperature fronts seen in the IMET sea surface temperature versus the equilibrator
temperature.  Despite the resetting of the PC clock, the equilibrator temperatures lagged the sea
surface temperatures by 3.6 min at the beginning of every leg.  This offset most likely represented
the real time for the water to travel from the pump to the equilibrator (i.e., the residence time of
the water in the ship).  The offset generally decreased with time to near zero by the end of the
longer cruises.  The changing offset was attributed to the notoriously bad clocks used in personal
computers, which could easily lose more then one minute per month.  Under the assumption that
the satellite time was correct, all of the xCO2 data were synchronized to the IMET data before
they were merged on the basis of a linear interpolation of the time offsets at the beginning and
the end of each leg.
     
     
                       3. QUALITY CONTROL
                                 
          
All of the water and air xCO2 measurements recorded during the Indian Ocean survey cruises
were presented in the OTL original (preliminary) data files.  Quality control (QC) flags (qflag)
were used to identify "bad" (qflag = 4) measurements (later these measurements were removed
from all data files), "questionable" (qflag = 3) measurements, and "good" (qflag = 2) 
measurements.  Although there are several individual readings that can ultimately lead to a bad
final value, one overall QC flag is reported for the measurement.  This section describes the
multilevel QC procedure performed by OTL and used to generate this flag.  As described in the
previous section, supporting measurements (sea surface temperature, salinity, and position) were
filtered for bad values and interpolated to the times of the CO2 measurements.  Anyone interested
in investigating the variability of these properties beyond its applicability to these CO2 data is
encouraged to return to the original IMET data set.
          
The first step in the calibration process was to normalize all of the detector CO2 voltages to
the mean detector temperature for that cruise and a pressure of one atmosphere.  The first step in
the QC protocols, therefore, was to remove any outliers in the detector temperature and pressure
readings.  Both of these measurements were very reliable with at most two to four isolated points
removed on any given leg.  Missing values were replaced with a linear approximation based on
adjacent values. 
          
The temperature- and pressure-normalized CO2 voltages for each of the standards were
analyzed for bad values.  The collection program's criteria for determining when a CO2 reading
is stable was purposefully generous to prevent undersampling of real variability in the sample
gases.  Because the stability criteria were the same for sample and standard gases, the first point
saved after switching to a new standard generally had not reached the equilibrium value.  After
visual confirmation of this phenomenon on each leg, the first point from each set of standards was
filtered from the data set.  Although rare, any exceptional outliers among the four remaining
measurements on each standard were also visually identified and removed.  The final calibration
at each time was based on the mean of the remaining values.
          
Before the final calibrated values were calculated, a QC check of the equilibrator
temperatures was performed.  These data were quality controlled by examining all of the points
recorded in 2-day intervals and outliers discarded based on visual inspection.  Values were
generally discarded when they were more than two standard deviations from a time local mean. 
The exact value for the cut, therefore, depended on the instrumental noise at the time. 
Questionable points were generally left in the data set.  Bad values were replaced with a linear
approximation based on adjacent values.
          
After calibration, the water and air data were broken into separate files.  At this stage, every
reading contributing to the water and air xCO2 values has been quality controlled with the
exception of the detector voltage.  Unusual readings in the final data, therefore, either reflected
real variability in the CO2 concentration of the sample or bad voltage readings.  Because it was
not always clear which was the case and the final QC step was somewhat based on subjective
ideas of how CO2 behaves in the ocean or atmosphere, QC flags were created for each
measurement.  Only values that were known to be bad (qflag = 4) were removed from the final
data set.
          
Marine air values showed little variability relative to the water measurements, which made
identification of outliers easy.  Values that were obvious outliers (qflag = 4) were visually
identified by plotting the data from an entire leg as a function of time.  High and variable values
recorded when the ship was near land were only flagged when there were known detector
problems since these values most likely represent real changes in atmospheric concentration. 
Questionable values (qflag = 3) were identified by carefully examining the data in 1- to 2-day
intervals and marking isolated points that did not follow the local trend.
          
xCO2 values in the surface seawater were generally much more variable than the marine air
readings.  A quality flag of "4" was reserved for water values that were clearly bad and for times
when the seawater supply was shut down for extended periods, but the automated CO2 system
continued to sample air from the equilibrator (I8S/I9S only).  Measurements marked with a quality
flag of "3" were either identified as data collected during brief bow pump failures or as single
outliers that clearly did not fit with the surrounding data.  The times of brief bow pump failure
were identified by using the analyst's notes and by plotting the sea surface temperature together
with the equilibrator temperature values as a function of time.  The two temperatures tracked each
other very well except when the bow pump shut down and the two temperature readings would
decouple.
          
The showerhead gas chromatograph (GC) underway xCO2 system designed by Ray Weiss
of SIO was running in parallel with the Princeton non-dispersive infrared (NDIR) instrument (see
Appendix A of printed documentation) during all nine Indian Ocean cruises aboard the R/V Knorr.  
Both systems shared the same marine air supply and took water from the uncontaminated bow pump 
plumbing at essentially the same point.  The sampling frequency of the two systems was very different. 

Approximately 25,000 water measurements and 8,000 air measurements were automatically logged
by the Princeton instrument along the 10,000-km cruise track of WOCE leg I9N (from Fremantle,
Australia, to Colombo, Sri Lanka).  By contrast, the SIO system made approximately 2,000 water
and air measurements (two samples per hour) on the same cruise.  The high sampling frequency
for the Princeton system (average water sample interval was 2.5 minutes) was designed to allow
examination of the small-scale spatial variability in surface xCO2 values.  Changes of 10 to
20 ppm over a distance of 10 km are not uncommon in open-ocean surface waters.  These
gradients can be an order of magnitude greater in frontal regions or in coastal waters.  Despite the
different designs of the two systems (e.g., GC vs NDIR and shower vs disk equilibrator) the
Princeton and SIO underway systems gave nearly identical results.  To make a fair comparison,
given the very different sampling rates, CO2 values were interpolated from each data set to 24
evenly distributed times per day (the top of every hour) for the entire cruise.  The range of surface
water CO2 concentrations covered in this comparison was approximately 300 to 420 ppm.  The
mean difference between the two systems (0.86  2.7 ppm) was not statistically different from
zero.  The standard deviation of the difference not only reflects the potential variability introduced
from the interpolations but also any real variability that may have been sampled by one system
and missed by the other.
     
     
                           4. RESULTS
                                 
          
Nearly 200,000 surface seawater and 50,000 marine air xCO2 measurements were made with
the Princeton underway system during the 14 months of the Indian Ocean survey.  With the
exception of leg I8S/I9S, all of the components of the system worked very well and the data are
believed to be of the highest quality.  This section briefly discusses the overall trends observed
in the data and any major events relevant to the final values.  All of the events described have
been carefully examined and appropriate action has been taken to maintain the quality of the data
presented in this report.  All times are reported in day of the year relative to 1995 with time of
day represented as a fractional day (i.e., noon on 1/1/95 = 1.5) to correspond directly with the
time stamp recorded with the data.
          
As mentioned previously, leg I8S/I9S was the most troublesome of the entire Indian Ocean
survey.  The R/V Knorr departed Fremantle, Australia, on December 1, 1994 (1995 day  29) with
the system functioning normally.  Aside from short system shutdowns due to overloading circuit
breakers, the system worked relatively well until day  20 when the ship encountered strong winds
and heavy seas.  The ship's bow pump system did not function properly when sea conditions
resulted in the uptake of large number of bubbles or when the inlet came completely out of the
water.  The bow pump was off and on for the next several days.  On day  11.33 the seawater
supply for the equilibrator was switched to a secondary pumping system that was thought to be
more reliable in rough weather.  The secondary system, however, significantly heated the water
before it reached the equilibrator.  The degree of heating was extremely variable and was, at
times, as much as 25C.  Although the degree of heating was documented in the difference
between the calibrated sea surface temperature and the equilibrator temperature, attempts to correct
the xCO2 values to in situ conditions yielded unrealistic results.  The data from the first 10 to 20
days of the cruise should be reliable.  However, most of the data collected after switching to the
secondary pump were deemed unreliable.  Although some data from the last 20 days
of the cruise appeared to be reasonable, care should be taken in placing too much confidence in
these results.
     
After the ship returned to Australia, the system was cleaned up and examined by C. Sabine
of PU.  Upon examination it was discovered that the CO2 signal from the detector was unusually
noisy (0.01V).  The noise problem was resolved by adjusting the setting on the rack temperature
controller from 35 to 33C.  It was later discovered that this model LiCor detector had a
substandard timing light emitting diode (LED) that was apparently in the process of failing. 
Lowering the temperature temporarily fixed the problem until the LED degraded enough to
become a problem at the lower temperature (several months later).  A replacement detector
provided by LiCor was installed at the end of leg I8N/I5E and operated for the rest of the survey. 
          
For leg I9N, lowering the rack temperature to 33C seemed to fix the problem.  The ship
departed Fremantle, Australia, on day 24.3333.  The water CO2 concentrations were generally
higher than the atmospheric concentrations for most of the cruise, with the exception of the Bay
of Bengal where some of the lowest CO2 concentrations of the survey were observed. 
The weather was generally calm, so very few problems were experienced with the bow pump. 
The reference gas was changed to tank ALM008242 on day 40.3993.  On day 59 a new data
collection program was installed that read and recorded the IMET and NAV data from the ship's
computer whenever a CO2 data point was collected.  Up to this time, the relevant IMET data were
extracted after the cruise from the ship's one-minute files.  The system was shut down on day
64.125 as the ship made its final approach to Sri Lanka.
          
Leg I8N/I5E left Sri Lanka on day 69.5366 and headed south.  The CO2 concentrations of
the waters south of Sri Lanka were generally 10 to 20 ppm higher than the atmospheric
concentrations, but dropped quickly to values very near atmospheric at around 10 S. The
system generally ran well throughout the cruise, although post-cruise analysis of data indicates that
the time spent trying to analyze the standards started getting significantly longer around day 82. 
The reason for this lengthening is not known since this phenomenon was not noticed while the
system was running.  It is possible that the system got noisy again most likely because of the
continued degradation of the timing LED in the detector.  The problem did not seem to affect the
data quality, only the length of time it took for the detector to stabilize and thus the quantity of
data collected. When the ship returned to port in Fremantle, Australia, the LiCor was replaced
with a new model from the factory.
         
Leg I3 was the first zonal leg of the survey.  The R/V Knorr left Fremantle, Australia, on
day 113.0040 and headed north along the Australian coast to approximately 20 S.  The surface
water CO2 concentrations near the Australian coast were variable, but after the ship turned west
there was a general decrease in CO2 concentration until approximately 135 E, then a slow
increase as the ship approached Madagascar.  The data gap between days 145 and 148
was the result of a short port stop in Mauritius.  Aside from the detector being changed before
the start of this leg, the only significant change to the system was a small modification to the
chemicals in the drying column.  Prior to this cruise, the chemical drying column was filled with
magnesium perchlorate.  Because it was difficult to determine when the perchlorate was becoming
saturated, all cruises after this point used a column made up half with magnesium perchlorate and
half with aquasorb (which changes from purple to black as it absorbs water).  The reference tank
was changed on day 144.2062, approximately 12 days before the end of the leg.
          
Leg I5W/I4 departed Mauritius on day 162.19 and returned on day 192 after a short port call
in Durban, South Africa, around day 172.  The surface water CO2 concentrations were
significantly lower than atmospheric concentrations for the entire leg.  The only
significant problems with the system were encountered around day 168 because of a temporary     
mechanical problem with the equilibrator and day 183 because of an extended bow pump shutdown 
caused by severe weather.
          
The R/V Knorr departed Mauritius on 196.3125 and headed north on leg I7N.  Surface
seawater CO2 concentrations increased from approximately 20 ppm below atmospheric
concentrations to approximately 20 ppm above atmospheric concentrations near 10 S. 
The highest CO2 concentrations (>600 ppm) were observed off the coast of Oman because of 
upwelling caused by the southwest monsoon.  The monsoon also made the seas very rough,
resulting in frequent bow pump failures.  The failures were generally short and care was taken to
flag the bad data.  The reference tank was changed twice during this cruise. The first tank was
replaced on day 206.4868 with a zero-CO2 reference (tank 24813) since the 200 ppm references
tanks were all exhausted.  Tank 24813 had apparently leaked in shipping since it started with a
pressure of only 700 psi.  The reference tank was changed again on day 227.3958 to tank 18260.
          
Leg I1 departed Oman on day 241.4167.  Before the system was started, the equilibrator was
thoroughly cleaned.  Unfortunately, during the cleaning the equilibrator PRT was broken.  It was
replaced with a spare that was calibrated to the initial PRT in post-cruise data processing.  The
high surface water CO2 values observed at the end of leg I7N were also observed at the beginning
of leg I1.  The surface values generally decreased as the ship sailed away from the
primary upwelling region.  The ship took a short break in Sri Lanka from day 271 to day 273
before continuing on to the Straits of Malacca.  The system was shut down as the ship entered
Indonesian waters on day 286.4.
          
All systems were shut down for the 3 weeks that the R/V Knorr spent undergoing repairs in
Singapore.  C. Sabine and G. McDonald boarded the ship on day 303 and thoroughly cleaned and
rebuilt the system during the transit from Singapore to Australia.  New calibrated reference gases
arrived at the ship, so tank ALM061365 was installed as the new reference gas.  The LiCor
detector also appeared to have had a slow drift in the zero voltage setting over its months of
operation.  The reference voltage had slowly drifted from 0.1 V when the detector was first set
up on leg I3 to nearly 0.6 V by the end of leg I1.  This voltage was reset to 0.1 before leg I10
using the zero adjust control on the LiCor.  The ship's electronic technician was changing the
IMET system around during the transit, so the underway system software had to be modified
accordingly.  The ship departed Dampier, Australia, for leg I10 on 315.2943.  The surface water
CO2 concentration decreased as the ship traveled south, then increased again as the ship turned
north.  The highest xCO2 values were observed in the Indonesian throughflow waters
at the northern end of the section.  The system was shut down on day 329.0104 as the ship
crossed into Indonesian territorial waters.  The only problem noted on the cruise was a loose
connector on the atmospheric pressure sensor on day 322.  The loose connector resulted in very
noisy pressure readings that, in turn, resulted in noisy pressure normalized voltages.  The bad
pressures during the affected time period (days 322.5 to 323.5) were replaced with the ship's
atmospheric pressure readings calibrated to match the underway system pressures preceding and
following the affected times.
          
The final leg of the survey, I2, started on day 339.2764 as the ship cleared the Indonesian
territorial waters.  The surface water CO2 concentration generally increased from east to west.  
The large data gap from day 361.5 to day 364.3 is the result of a port stop in Diego Garcia.  
The smaller gaps resulted from frequent system crashes caused by the inconsistent transmission of 
the IMET data by the ship's computers.  The Indian Ocean survey ended in Mombasa, Kenya, on day 
386.6076 after covering a total distance of ~92,000 km.
     



     5. DATA CHECKS AND PROCESSING PERFORMED BY CDIAC
                                
                                   
An important part of the NDP process at the CDIAC involves the quality assurance (QA) of
data before distribution.  Data received at CDIAC are rarely in a condition that would permit
immediate distribution, regardless of the source.  To guarantee data of the highest possible quality,
CDIAC conducts extensive QA reviews  that involve examining the data for completeness,
reasonableness, and accuracy.  Although they have common objectives, these reviews are tailored
to each data set and often require extensive programming efforts.  In short, the QA process is a
critical component in the value-added concept of supplying accurate, usable data for researchers. 
          
The following information summarizes the data-processing and QA checks performed by
CDIAC on the underway data obtained during the R/V Knorr Expeditions in the Indian Ocean
(WOCE 9 Sections).
     
     1.   All underway measurements were provided to CDIAC as 18 ASCII-formatted files (9 for
          surface seawater and 9 for marine air CO2 measurements) by Chris Sabine and Robert Key
          of PU.  A FORTRAN 77 retrieval program was written and used to reformat the original
          files into uniform formats for "water" and "air" data files.
     
     2.   All individual "water" and "air" data files were merged into single "water" and single "air"
          files that were sorted and arranged chronologically.
     
     3.   All data were plotted to check for obvious outliers.  Several outliers were identified and
          removed after consultation with the principal investigators.
     
     4.   All data that were marked by quality flag "4" as bad data in original files were removed after
          consultation with the principal investigators.
     
     5.   Dates and times were checked for bogus values (e.g., values of MONTH <1 or >12, DAY
          <1 or >31, YEAR <1994 or >1996, TIME <0000 or >2400.
     
     6.   All cruise tracks were plotted using the coordinates presented in data files and compared with
          the maps and cruise information supplied by C. Sabine and R. Key.
         




       6.  HOW TO OBTAIN THE DATA AND DOCUMENTATION
                                 
        
This database is available on request in machine-readable form, without charge, from CDIAC. 
CDIAC will also distribute subsets of the database as needed.  It can be acquired on 9-track
magnetic tape; 8-mm tape; 150-MB, 0.25-in. tape cartridge; MAC- or IBM-formatted floppy
diskettes; or from CDIAC's anonymous file transfer protocol (FTP) area via the Internet (see FTP
address below).  Requests should include any specific media instructions required by the user to
access the data (e.g., 1600 or 6250 BPI, labeled or nonlabeled, ASCII or EBCDIC characters, and
variable- or fixed-length records; 3.5- or 5.25-in. floppy diskettes, high or low density; and 8200
or 8500 format, 8-mm tape).  Magnetic tape requests not accompanied by specific instructions will
be filled on 9-track, 6250-BPI, nonlabeled tapes with ASCII characters.  Requests should be
addressed to
     
        Carbon Dioxide Information Analysis Center
        Oak Ridge National Laboratory
        P.O. Box 2008
        Oak Ridge, TN 37831-6335
        U.S.A.
     
              Telephone:                                    423-574-0390 or 423-574-3645
              Fax:                                          423-574-2232
     
              Electronic mail:                              cdiac@ornl.gov
     
     
     The data files may also be acquired from CDIAC's anonymous FTP area via the Internet:
     
     FTP to cdiac.esd.ornl.gov (128.219.24.36),
     enter "ftp" or "anonymous" as the user ID,
     enter your electronic mail address as the password (e.g.,"alex@esd.ornl.gov"),
     change to the directory "/pub/ndp064," and
     acquire the files using the FTP "get" or "mget" command.

As an alternative, the data can be accessed through the following World Wide Web site:
http://cdiac.esd.ornl.gov/oceans/doc.html.


                      7. ACKNOWLEDGEMENTS

    
C. Sabine and R. Key would like to thank all of the members of the DOE CO2 survey team 
for helpful advice while they were building the underway system and for helping to run the
system during the Indian Ocean survey.  In particular they thank R. Weiss and R. Van Woy for
calibration of standard gases and the captain and crew of the R/V Knorr for assistance throughout
the survey.  They also thank the chief scientists from each leg as well as the U.S. WOCE
Hydrographic Programme Office for their assistance and cooperation with the underway
measurements.  This work was supported by a grant from the U.S. DOE's Office of Biological
and Environmental Research (DE-FG02-93ER61540) and the Princeton University Department of
Geosciences.


                          8. REFERENCES

Lewis, E. L. 1980.  The practical salinity scale 1978 and its antecedents.  IEEE J. Ocean. Eng.
     OE-5:3 8.

Sabine, C. L., and R. M. Key.  1996.  A new instrument design for continuous determination of
     oceanic pCO2. Tech. Rep. 96-12, Ocean Tracers Laboratory, Dept. of Geosciences, Princeton
     University, Princeton, New Jersey.

Weiss, R. F.  1981.  Determinations of carbon dioxide and methane by dual catalyst flame
     ionization chromatography and nitrous oxide by electron capture chromatography.  J. Chrom.
     Sci., 19:611-16.

Weiss, R. F., R. A. Janke, and C. D. Keeling.  1982.  Seasonal effects of temperature and salinity
     on partial pressure of CO2 in seawater. Nature, 300:511-13.







                             PART 2:

                 CONTENT AND FORMAT OF DATA FILES                      



                       9. FILE DESCRIPTIONS
                                
This section describes the content and format of each of the 23 files that make up this NDP
(see Table 4).  Because CDIAC distributes the data set in several ways (e.g., via anonymous FTP,
on floppy diskette, and on 9-track magnetic tape), each of the 23 files is referenced by both an
ASCII file name, which is given in lowercase, boldfaced type (e.g., ndp064.doc), and a file
number.  The remainder of this section describes (or lists, where appropriate) the contents of each
file.  The files are discussed in the order in which they appear on the magnetic tape.


        Table 4.  Content, size, and format of data files
                                                                 

------------------------------------------------------------------------------------------- 
    File number, name,                  Logical        File size        Block        Record
    and description                     records        in bytes         size         length
-------------------------------------------------------------------------------------------
1.  ndp064.doc:                          1,426          90,106          8,000           80
    a detailed description
    of the cruise network, the
    two FORTRAN 77 data-
    retrieval routines, and the
    20 oceanographic data files

          
2.  xco2airdat.for:                         44           1,515          8,000           80
    a FORTRAN 77 data-retrieval
    routine to read and print any of
    *air.dat files

3.  xco2waterdat.for:                       48           1,744          8,000           80
    a FORTRAN 77 data-retrieval
    routine to read and print any of
    *water.dat files

4.  IOxco2air.dat                       45,838       4,766,850          6,850          137
    underway marine air xCO2 and 
    surface hydrographic data 
    from all nine Indian Ocean 
    survey cruises

5.  IOxco2water.dat:                   187,035      24,688,183          6,850          137
    underway surface seawater xCO2,
    interpolated atmospheric xCO2, and
    underway hydrographic data from all 
    nine Indian Ocean survey cruises
            
6.  i8si9sair.dat:                       4,809         499,834          6,850          137
    underway marine air xCO2 and 
    surface hydrographic data from
    Indian Ocean WOCE section 
    I8S/I9S

7.  i8si9swater.dat:                    10,481       1,383,055           6,850         137
    underway surface seawater xCO2,
    interpolated atmospheric xCO2, and
    underway hydrographic data from 
    Indian Ocean WOCE section 
    I8S/I9S

8.  i9nair.dat:                          7,632         793,426           6,850         137
    underway marine air xCO2 and 
    surface hydrographic data from
    Indian Ocean WOCE section 
    I9N

9.  i9nwater.dat:                       25,077       3,309,727           6,850          137
    underway surface seawater xCO2,
    interpolated atmospheric xCO2, and
    underway hydrographic data from 
    Indian Ocean WOCE section 
    I9N

10. i8ni5eair.dat:                       4,519         469,674           6,850          137
    underway marine air xCO2 and 
    surface hydrographic data from
    Indian Ocean WOCE section 
    I8N/I5E
    
11. i8ni5ewater.dat:                    14,021       1,850,335           6,850          137
    underway surface seawater xCO2,
    interpolated atmospheric xCO2, and
    underway hydrographic data from 
    Indian Ocean WOCE section 
    I8N/I5E
       
12. i3air.dat:                           6,430         668,418           6,850          137
    underway marine air xCO2 and 
    surface hydrographic data from
    Indian Ocean WOCE section 
    I3
    
13. i3water.dat:                        30,552       4,032,427           6,850          137
    underway surface seawater xCO2,
    interpolated atmospheric xCO2, and
    underway hydrographic data from 
    Indian Ocean WOCE section 
    I3                          
      
14. i5wi4air.dat:                        4,388         456,050           6,850          137
    underway marine air xCO2 and 
    surface hydrographic data from
    Indian Ocean WOCE section 
    I5W/I4
    
15. i5wi4water.dat:                     20,423       2,695,399           6,850          137
    underway surface seawater xCO2,
    interpolated atmospheric xCO2, and
    underway hydrographic data from 
    Indian Ocean WOCE section 
    I5W/I4
    
16. i7nair.dat:                          5,847         607,786           6,850          137
    underway marine air xCO2 and 
    surface hydrographic data from
    Indian Ocean WOCE section 
    I7N
    
17. i7nwater.dat:                       29,833       3,937,519           6,850          137
    underway surface seawater xCO2,
    interpolated atmospheric xCO2, and
    underway hydrographic data from 
    Indian Ocean WOCE section 
    I7N
    
18. i1air.dat:                           6,257         650,426           6,850          137
    underway marine air xCO2 and 
    surface hydrographic data from
    Indian Ocean WOCE section 
    I1
    
19. i1water.dat:                        28,248       3,728,299           6,850          137
    underway surface seawater xCO2,
    interpolated atmospheric xCO2, and
    underway hydrographic data from 
    Indian Ocean WOCE section 
    I1                          
      
20. i10air.dat:                          1,910         198,338           6,850          137
    underway marine air xCO2 and 
    surface hydrographic data from
    Indian Ocean WOCE section 
    I10
    
21. i10water.dat:                        8,399        1,108,231          6,850          137
    underway surface seawater xCO2,
    interpolated atmospheric xCO2, and
    underway hydrographic data from 
    Indian Ocean WOCE section 
    I10
    
22. i2air.dat:                           4,102          426,306          6,850          137
    underway marine air xCO2 and 
    surface hydrographic data from
    Indian Ocean WOCE section 
    I2
    
23. i2water.dat:                        20,057        2,647,087          6,850          137
    underway surface seawater xCO2,
    interpolated atmospheric xCO2, and
    underway hydrographic data from 
    Indian Ocean WOCE section 
    I2                                  
                                        _____         _________                               
      Total                              2445        10,119,198
                                                             
    

9.1 ndp064.doc (File 1)
    
This file contains a detailed description of the data set,  the two FORTRAN 77 data retrieval
routines, and the 20 oceanographic data files.  It exists primarily for the benefit of individuals 
who acquire this database as machine-readable data files from CDIAC.
    
    
    
9.2 xco2airdat.for (File 2)
    
This file contains a FORTRAN 77 data-retrieval routine to read and print all *air.dat files. 
The following is a listing of this program.  For additional information regarding variable
definitions, variable lengths, variable types, units, and codes, please see the description for 
*air.dat files. 
    
    c*********************************************************************
    c* This is a Fortran 77 retrieval code to read and format the underway   
    c* air xCO2 and hydrographic measurements from the WOCE Indian Ocean
    c* survey cruises (*air.dat files)
    c********************************************************************* 
    
           INTEGER  flag
           REAL jday, atmpre, airxco2, lat, lon, temp, sal
           CHARACTER sect*11, date*8, time*8
           OPEN (unit=1, file='input.dat')
           OPEN (unit=2, file='output.dat')
           write (2, 5)
    
     5     format (2X,'SECTION',7X,'DATE',6X,'TIME',4X,'JULIAN',2X,
         1 'ATM_PRES',5X,'XCO2',5X,'XCO2',2X,'LATIT',3X,'LONGIT',3X,
         2 'SUR_TMP',2X,'SUR_SAL',/,5X,'#',11X,'GMT',7X,'GMT',5X,'DATE',
         3 6X,'ATM',3X,'DRY_AIR_PPM',1X,'QC_FL',3X,'DCM',6X,'DCM',5X,
         4 'DEG_C',5X,'PSS',/)
    
           read (1, 6)
     6     format (//////)
    
     7     CONTINUE    
           read (1, 10, end=999) sect, date, time, jday, atmpre, airxco2,
         1 flag, lat, lon, temp, sal
    
     10    format (1X, A11, 2X, A8, 2X, A8, 2X, F7.3, 2X, F7.5, 3X, F7.3,  
         1 5X, I1, 2X, F8.4, 1X, F8.4, 2X, F7.4, 2X, F7.4)
     
           write (2, 20) sect, date, time, jday, atmpre, airxco2,
         1 flag, lat, lon, temp, sal
    
     20    format (1X, A11, 2X, A8, 2X, A8, 2X, F7.3, 2X, F7.5, 3X, F7.3, 
         1 5X, I1, 2X, F8.4, 1X, F8.4, 2X, F7.4, 2X, F7.4)
    
           GOTO 7
     999   close(unit=5)    
           close(unit=2)
           stop
           end
    
    
    
    
9.3 xco2waterdat.for (File 3)
    
This file contains a FORTRAN 77 data-retrieval routine to read and print all *water.dat files.  The
following is a listing of this program.  For additional information regarding variable definitions,
variable lengths, variable types, units, and codes, please see the description for *water.dat files.
      
    
    c*********************************************************************
    c* This is a Fortran 77 retrieval code to read and format the underway   
    c* surface seawater xCO2 and hydrographic measurements from the WOCE
    c* Indian Ocean survey cruises (*water.dat files)
    c*********************************************************************
      
           INTEGER  flag
           REAL jday, equitmp, atmpre, eqxco2, lat, lon
           REAL temp, sal, xco2sst, eaxco2
           CHARACTER sect*11, date*8, time*8
           OPEN (unit=1, file='input.dat')
           OPEN (unit=2, file='output.dat')
           write (2, 5)
    
     5     format (2X,'SECTION',7X,'DATE',6X,'TIME',5X,'JULIAN',2X,
         1 'EQUIL_TMP',2X,'ATM_PRES',3X,'XCO2_DRY_AIR',4X,'XCO2',2X,
         2 'LATIT',3X,'LONGIT',3X,'SUR_TMP',2X,'SUR_SAL',1X,
         3 'XCO2_DRY_AIR', 1X, 'EST_ATM_XCO2',/,5X,'#',11X,'GMT',7X,
         4 'GMT',6X,'DATE',5X,'DEG_C',6X,'ATM',4X,'AT_EQUIL_TMP_PPM',
         5 1X,'QC_FL',3X,'DCM',6X,'DCM',5X,'DEG_C',5X,'PSS',4X,
         6 'AT_SST_PPM',2X,'DRY_AIR_PPM',/)
    
           read (1, 6)
     6     format (//////)
    
     7     CONTINUE    
           read (1, 10, end=999) sect, date, time, jday, equitmp, 
         1 atmpre, eqxco2, flag, lat, lon, temp, sal, xco2sst, eaxco2
    
     10    format (1X, A11, 2X, A8, 2X, A8, 2X, F7.3, 3X, F7.4, 4X,
         1 F7.5, 5X, F7.3, 8X, I1, 2X, F8.4, 1X, F8.4, 2X, F7.4, 2X,
         2 F7.4, 4X, F7.3, 5X, F7.3)
     
           write (2, 20) sect, date, time, jday, equitmp, 
         1 atmpre, eqxco2, flag, lat, lon, temp, sal, xco2sst, eaxco2
    
     20    format (1X, A11, 2X, A8, 2X, A8, 2X, F7.3, 3X, F7.4, 4X, 
         1 F7.5, 5X, F7.3, 8X, I1, 2X, F8.4, 1X, F8.4, 2X, F7.4, 2X,
         2 F7.4, 4X, F7.3, 5X, F7.3)
    
           GOTO 7
     999   close(unit=5)    
           close(unit=2)
           stop
           end
    
        

9.4 *air.dat files
    
These 10 data files contain the underway marine air xCO2 measurements and sea surface
hydrographic data collected during the WOCE Indian Ocean survey cruises.  All files have the
same format and can be read by using the following FORTRAN 77 code [contained in
xco2airdat.for (File 2)]:
    
           
           INTEGER  flag
           REAL jday, atmpre, airxco2, lat, lon, temp, sal
           CHARACTER sect*11, date*8, time*8
    
           read (1, 10, end=999) sect, date, time, jday, atmpre, airxco2,
         1 flag, lat, lon, temp, sal
    
     10    format (1X, A11, 2X, A8, 2X, A8, 2X, F7.3, 2X, F7.5, 3X, F7.3,  
         1 5X, I1, 2X, F8.4, 1X, F8.4, 2X, F7.4, 2X, F7.4)
    
    
    
    Stated in tabular form, the contents include the following
                                                             
                                                             
    
    Variable           Variable      Variable       Starting    Ending
                         type        width          column      column
                                                             
    
    sect               Character       11               2          12
    date               Character        8              15          22
    time               Character        8              25          32
    jday                Numeric         7              35          41
    atmpre              Numeric         7              44          50
    airxco2             Numeric         7              54          60
    flag                Numeric         1              66          66
    lat                 Numeric         8              69          76
    lon                 Numeric         8              78          85
    temp                Numeric         7              88          94
    sal                 Numeric         7              97         103
                                                             
    
    The variables are defined as follows:
    
    sect       is the WOCE section number;
    
    date       is the sampling date (month/day/year);
    
    time       is the sampling time (GMT);
    
    jday       is the julian day of the year relative to 1995 with time of the day represented
               as a fractional day (i.e. noon on 1/1/95=1.5);
    
    atmpre     is the atmospheric pressure (atm);
    
    airxco2    is the observed mole fraction of CO2 in air [ppm (dry air)];
    
    flag       is the airxco2 data quality flag:
               2 = acceptable measurement of airxco2;
               3 = questionable measurements of airxco2;
    
    lat        is the latitude of the sampling location (decimal degrees; negative values
               indicate the Southern Hemisphere);
    
    lon        is the longitude of the sampling location (decimal degrees; negative values
               indicate the Western Hemisphere);
    
    temp       is the sea-surface temperature (C);
    
    sal        is the sea-surface salinity [on the Practical Salinity Scale (PSS)].
    
    
    
    9.5 *water.dat files 
    
        
These 10 data files containing the underway surface seawater xCO2, atmospheric xCO2
concentrations interpolated to the times when water measurements were made, and hydrographic
measurements collected during WOCE Indian Ocean survey cruises.  All files have the same
format and can be read by using the following FORTRAN 77 code [contained in xco2waterdat.for
(File 3)]:
      
           
           INTEGER  flag
           REAL jday, equitmp, atmpre, eqxco2, lat, lon
           REAL temp, sal, xco2sst, eaxco2
           CHARACTER sect*11, date*8, time*8
    
           read (1, 10, end=999) sect, date, time, jday, equitmp, 
         1 atmpre, eqxco2, flag, lat, lon, temp, sal, xco2sst, eaxco2
    
     10    format (1X, A11, 2X, A8, 2X, A8, 2X, F7.3, 3X, F7.4, 4X,
         1 F7.5, 5X, F7.3, 8X, I1, 2X, F8.4, 1X, F8.4, 2X, F7.4, 2X,
         2 F7.4, 4X, F7.3, 5X, F7.3)
    
    
    Stated in tabular form, the contents include the following:
    
                                                             
    
                       Variable      Variable       Starting    Ending
    Variable             type        width          column      column
                                                             
    
    sect               Character       11               2          12
    date               Character        8              15          22
    time               Character        8              25          32
    jday                Numeric         7              35          41
    equitmp             Numeric         7              45          51
    atmpre              Numeric         7              56          62
    eqxco2              Numeric         7              68          74
    flag                Numeric         1              83          83
    lat                 Numeric         8              86          93
    lon                 Numeric         8              95         102
    temp                Numeric         7             105         111
    sal                 Numeric         7             114         120
    xco2sst             Numeric         7             125         131
    eaxco2              Numeric         7             137         143
                                                             
    
    The variables are defined as follows:
    
    sect       is the WOCE section number;
    
    date       is the sampling date (month/day/year);
    
    time       is the sampling time (GMT);
    
    jday       is the julian day of the year relative to 1995 with time of the day represented
               as a fractional day (i.e., noon on 1/1/95 = 1.5);
    
    equitmp    equilibrator temperature (C);
    
    atmpre     is the atmospheric pressure (atm);
    
    eqxco2     is the observed mole fraction of CO2 in surface seawater at the equilibrator
               temperature [ppm (dry air)];
    
    flag       is the eqxco2 data quality flag:
               2 = acceptable measurement of eqxco2;
               3 = questionable measurements of eqxco2;
    
    lat        is the latitude of the sampling location (decimal degrees; negative values
               indicate the Southern Hemisphere);
    
    lon        is the longitude of the sampling location (decimal degrees; negative values
               indicate the Western Hemisphere);
    
    temp       is the sea-surface temperature (C);
    
    sal        is the sea-surface salinity (PSS);
    
    
  xco2sst      is the mole fraction of CO2 in surface seawater corrected to sea surface
               temperature [ppm (dry air)].  Temperature correction was determined from
               the equations of Weiss et al. (1982);
    
    eaxco2     is the atmospheric xCO2 concentrations interpolated to the times when water
                   measurements were made [ppm (dry air)].