




                        1992 CRUISE REPORT FOR WOCE PR16:  
                     A REPEAT HYDROGRAPHIC SECTION ALONG 110W


     A.  CRUISE NARRATIVE


     A.1  HIGHLIGHTS

     Expedition Designation (EXPOCODE):  31DSEP692/2
     Co-Chief Scientist:  Rik Wanninkhof
			  NOAA Atlantic Oceanographic and Meteorological Lab
			  4301 Rickenbacker Causeway
			  R/E/AO/OCD
		          Miami, FL  33149-1026
			  Telephone:  (305)361-4379
			  Telefax:  (305)361-4582
			  Internet:  wanninkhof@aoml.erl.gov
     Co-Chief Scientist:  Linda J. Mangum
                          NOAA Pacific Marine Environmental Laboratory
		          7600 Sand Point Way NE
		          Bin C15700 R/E/PM
		          Seattle, WA  98115-0070
		          Telephone:  (206)526-6740
	                  Telefax:  (206)526-6744
		          Internet:  mangum@noaapmel.gov
     Ship:  NOAA Discoverer, R-102
     Ports of Call:  Manzanillo, Mexico - Salinas, Ecuador
     Cruise Dates:  October 12 to November 18, 1992


     A.2  CRUISE SUMMARY

     Cruise Tracks

          Figure 1 shows the cruise track and CTD/rosette station locations 
     for 31DSEP692/2.

     Number of Stations

          Thirty-one CTD/rosette profiles were collected on leg 2 of the fall
     EPOCS/TOGA/CO2/JGOFS cruise (31DSEP692/2) using a Neil Brown Mark IIIb 
     CTD and General Oceanics 24 bottle rosette equipped with 24 10-liter 
     Niskin water sample bottles.  Twenty-eight of the 31 profiles were 
     collected along 110W from 10S to 10N. 

     Rosette Sampling

          During 31DSEP692/2, all 24 Niskin bottles were sampled for salinity
     each cast, with a duplicate salinity sample taken from the deepest 
     bottle to monitor the drift of the Autosal instrument.  Other samples
     taken from the Niskin bottles included dissolved oxygen, seawater CO2
     partial pressure (pCO2), total CO2 (TCO2), total alkalinity (TALK), 
     dissolved organic carbon and nitrogen, chlorophyll, particulate organic
     carbon and nitrogen, and nutrients.  Nominal sampling depths were 1000(2),
     800, 600, 400, 300, 250, 200, 180, 160, 150, 140, 130, 120, 110, 100,
     90, 80, 60, 50, 40, 20, 10, and 0 meters.  Twenty-six casts were to a 
     depth of 1000 meters, and 3 casts were to 150 meters.  Bottle sample 
     depths for 31DSEP692/2 are shown in figure 2.

     Moorings

          Beginning 31DSEP692/2, a pressure/temperature gauge (PTG) was
     recovered and deployed in approximately 100 feet of water off Clipperton
     Island at approximately 10N, 110W.  ATLAS mooring operations were 
     conducted at 8N (recovery/deployment), 5N (repair), 2N (recovery/deploy-
     ment), and 2S (recovery/deployment) along 110W.  ATLAS moorings at 5S
     and 8S were inspected and found to be in good condition.  ATLAS moorings 
     were also deployed at new sites at 2S, 0N, and 2N along 95W.  An equatorial 
     current meter mooring was recovered and redeployed at 0N, 110W.
     

     A.3  LIST OF PRINCIPAL INVESTIGATORS
     	
          Dr. Mike McPhaden, NOAA/PMEL    moorings
	  Dr. Richard Feely, NOAA/PMEL    CO2
	  Dr. Rik Wanninkhof, NOAA/AOML   CO2
          Dr. Don Hansen, NOAA/AOML	  drifting buoys
	  Dr. Don Atwood, NOAA/AOML       CO2, nutrients
	  Dr. Doug Wilson, NOAA/AOML      CTD
	  Dr. Ken Buesseler, WHOI	  Th-234
	  Dr. Ed Peltzer, WHOI		  DOC
	  Dr. Francisco Chavex, MBARI	  plankton biology
	  Dr. Pat Wheeler, OSU	 	  productivity 
	  Dr. Frank Millero, UM/RSMAS     total alkalinity

     Abbreviations
          NOAA  National Oceanic and Atmospheric Administration
	  PMEL  Pacific Marine Environmental Laboratory, Seattle, WA
	  AOML  Atlantic Oceanographic and Meteorological Laboratory, Miami, FL
	  WHOI  Woods Hole Oceanographic Institution, Woods Hole, MA
	  MBARI Monterey Bay Aquarium Research Institute, Monterey Bay, CA
	  OSU   Oregon State University, Newport, OR
	  UM    University of Miami, Miami, FL
	  RSMAS Rosenstiel School of Marine and Atmospheric Science, Miami, FL


     A.4  SCIENTIFIC PROGRAMME AND METHODS

          The NOAA-sponsored Equatorial Pacific Ocean Climate Studies (EPOCS)
     and Tropical Ocean and Global Atmosphere (TOGA) research programs are
     designed to further understanding of the role of the tropical ocean in 
     modifying the world's climate.  A primary goal of this research is to 
     investigate the dominant mechanisms that produce large scale, interannual
     variations of sea surface temperature in vast regions of the tropical 
     Pacific Ocean.  Studies indicate that such sea surface temperature 
     anomalies are linked to perturbations in the mid-latitude atmospheric 
     pressure fields and hence to weather.

          Ocean currents play an important role in determining the local 
     temperature change through heat advection.  Therefore, an associated goal
     of the EPOCS/TOGA program is to study the horizontal, vertical and 
     temporal variations of the currents and how they are affected by the wind
     field.  Variability in currents, temperature, and winds are studied using
     numerous techniques including current meter moorings, thermistor chain 
     moorings (ATLAS), underway acoustic doppler current profiling (ADCP), CTD
     profiles, drifting buoys, and other shipboard physical oceanographic and 
     meteorological measurements.

          The NOAA Office of Global Programs (OGP) has sponsored the Ocean-
     Atmosphere Carbon Dioxide Exchange (CO2) program in order to examine the 
     rate at which CO2 is taken up and released by the oceans.  Research is 
     designed to determine the relative effects of biological fixation of
     carbon within the zone of equatorial upwelling, ther vertical flux of 
     that fixed carbon to abyssal depths, and the outgassing CO2.  
   
          The focus of the joint National Science Foundatation (NSF)/NOAA
     sponsored U.S. Joint Global Ocean Flux Studies (JGOFS) is to determine
     the relationship between the biogeochemical cycles of carbon and 
     nitrogen species and physical forcing in the upper ocean.

          The primary objectives of 31DSEP692/2 were to maintain the array of 
     near-equatorial ATLAS and current meter moorings along 110W and 95W in 
     the eastern tropical Pacific, conduct hydrographic measurements in the
     area, and determine the concentrations of carbon species in the area with 
     attendant modeling the flux of carbon through the system.

          Temperature (figure 3) and salinity (figure 4) sections along 110W 
     for 31DSEP692/2 show warm water throughout the section, with surface 
     water warmer than 25C north of 1N.  A well-developed thermocline exists
     around 100 db, with the 15C isotherm sloping to about 175 db from 4S to
     10S.  The equatorial undercurrent appears south of the equator.

          Figure 5 shows the TS relationship between CTD casts taken along 
     110W during 31DSEP692/2.  Salinity sample data are overplotted on each.

          A description of the methods of measurement, calibration and proces-
     sing of the NBIS CTD/O2 data is given in section C.2 of this report.


     A.5  PROBLEMS ENCOUNTERED ON THE CRUISE

          Twenty-eight casts were made from 10N to 10S along 110W.  AOML Neil
     Brown Mark IIIb CTD #4 and 24-bottle rosette sampler was used for the 
     first 18 casts of this leg before the package was lost at 4S, 110W when 
     the cable parted with 950 meters out.  The remaining casts employed AOML
     Neil Brown Mark IIIb CTD #1 and 12-bottle rosette sampler.  Two casts
     were done at each station (0-150 m and 175-1000 m) to cover the same
     sampling depths as the 24-bottle package.


     A.6  OTHER INCIDENTS OF NOTE


     A.7  LIST OF CRUISE PARTICIPANTS

	  Dr. Rik Wanninkhof, NOAA/AOML	 	Co-Chief Scientist
          Ms. Linda Mangum, NOAA/PMEL    	Co-Chief Scientist
          Mr. Rick Miller, NOAA/PMEL     	ATLAS moorings
	  LT. Dave Zimmerman, NOAA/PMEL  	current meter moorings
	  Mr. Lloyd Moore, NOAA/AOML	 	nutrients
	  Mr. George Berberian, NOAA/AOML	nutrients
	  Mr. Gregg Thomas, NOAA/AOML		CTD operations, salinity
	  Mr. Robert Roddy, NOAA/AOML		CTD operations, oxygen
 	  Mr. Mike Shoemaker, NOAA/AOML		electronics
	  Mr. Mat Steckley, NOAA/AOML		pCO2
	  Mr. Hua Chen, NOAA/AOML/RSMAS		pCO2
	  Mr. David Jones, NOAA/AOML		TCO2
	  Mr. Thomas Lantry, NOAA/AOML		TCO2
	  Ms. Coleen O'Keefe, MBARI		phytoplankton biology
	  Ms. Cindy Venn, MBARI			phytoplankton biology
	  Ms. Rachel Zimmerman, MBARI		plankton biology
	  Ms. Leslie Redmond, WHOI		DOC
	  Ms. Mary Hartman, WHOI		Th-234
	  Mr. Sanjay Mane, UM/RSMAS		total alkalinity, TCO2
	  Mr. David Purkerson, UM/RSMAS		total alkalinity, TCO2
	  Mr. Kitack Lee, UM/RSMAS		total alkalinity, TCO2
	  Mr. Marcellino Suzuki, OSU		productivity
	  Mr. Scott Libby, OSU			productivity


     B.  UNDERWAY MEASUREMENTS

     
     B.1  XBT

          XBT measurements were made in accordance with SEAS instructions
     (5.2.1).  XBT data were collected and transmitted via the ship's SEAS
     unit.  For each XBT cast, the following information was recorded on log
     sheets:  wind direction, wind speed, barometric pressure, air temperature,
     bucket temperature, intake temperature, time, and ship's position.  XBTs
     from the scientific party's supply were launched by the Survey Department
     at the discretion of the Chief Scientist.
     

     B.2  ADCP

          Aboard the NOAA ship Discoverer, the ADCP was interfaced with a
     Magnavox GPS navigator and received data at 2 second intervals through
     the selection of code 208, data control option 1.  Accurate ship 
     navigation is essential to absolute ADCP current measurements.  The
     ship provided a fully operational Magnavox 1107 TRANSIT/GPS navigator 
     with an atomic frequency standard throughout the cruise.  The ship's
     Survey Department was responsible for changing data disks as necessary.


     B.3  SST AND SSS

          Near sea surface temperature (SST) and salinity (SSS) measurements 
     were recorded continuously throughout the cruise using a thermosalino-
     graph accurate to within 0.1C and 0.01 psu.  The Survey Department 
     translated the data from the thermosalinograph to ASCII listings and
     plots daily.  Bucket temperature and salinity samples were collected with
     each XBT and the continuous record annotated with the date/time and 
     bucket temperature.  


     B.4  SEAWATER SAMPLING

          Continuous water sampling was conducted using the ship's bow intake
     system capable of delivering 100 liters per minute of seawater to the
     Oceanographic Laboratory, where a sea/air equilibrator system was located.
     Care was taken to prevent contamination from smoke, solvent fumes, 
     cleaning solutions, etc.


     B.5  ATMOSPHERIC SAMPLING

          Air samples were collected from the bow.  In order to minimuze 
     contamination, no deck work or smoking was allowed forward of the main
     exhaust stack.  A mast was extended approximately 7 meters upward from
     G-deck to the level of the Bridge for the air sampling lines.  Air
     sampling lines ran from the mast to the Oceanographic Laboratory.


     C.  DESCRIPTION OF MEASUREMENT TECHNIQUES AND CALIBRATIONS


     C.1  SAMPLE SALINITY MEASUREMENTS (Gregg Thomas, AOML)

          The salinity analysis of samples was carried out exclusively on
     Guildline Autosal salinometers (model 8400A).  The instruments were
     operated in the ship's constant temperature laboratory at a bath 
     temperature of 24C.  Standardization was effected by use of IAPSO 
     Standard Seawater batch P1??.  The commonly accepted precision of the 
     Autosal is 0.001 psu, with an accuracy of 0.003 psu.  The Autosals
     were standardized before and after each run.  The drift during each run 
     was monitored and individual samples were corrected for the drift during 
     each run by linear interpolation.  Bottle salinities were compared with 
     computed CTD salinities to identify leaking bottles, as well as to 
     monitor the conductivity sensor performance and drift. "Agreement between
     bottle salinity and CTD salinity was excellent.  For the shallow water
     CTD (AOML #4), the sensor derived salinity was on average 3 to 5 parts
     per million (ppm) saltier, and for the deep CTD (AOML #1) used after the
     loss of the shallow underwater unit, the sensor read 3 to 5 ppm fresher
     than corresponding bottle values."

Note: SALNTY quality flag not available from OCDMS data base.


     C.2  CTD MEASUREMENTS 

     Equipment

          The fall EPOCS/TOGA/CO2/JGOFS cruise shallow (0-1600 db) underwater 
     package was comprised of a Neil Brown Mark IIIb CTD, a General Oceanics 
     24-bottle rosette, and 24 10-liter Nisken water sample bottles.  A .322 
     inch diameter conducting cable was used on an Interocean winch to lower 
     and raise the package.  Data from the underwater unit was transmitted in 
     real time to a shipboard data terminal through the 3-conductor electro-
     mechanical cable in TELETYPE (TTY) format using a frequency shift key 
     (FSK) modulated signal superimposed on the DC power supplied to the 
     underwater unit.  A Neil Brown 1150 deck unit was used to receive,
     demodulate, and convert the data.  

     Standards 

          The EG&G conductivity sensor has a range of 1 to 65 mmho, an 
     accuracy of +/- 0.005 mmho, resolution of 0.001 mmho, and stability
     of 0.003 mmho/month.  The Rosemount platinum thermometer has a range  
     of -32 to 32 C, an accuracy of +/-0.005 C (-3 to 32 C), resolution of 
     0.0005 C, and stability of 0.001 C/month.  The deep water Paine pressure 
     sensor has a range of 0 to 6500 db, an accuracy of +/- 6.5 db, resolution
     of 0.1 db, and stability of 0.1%/month.  

     CTD Data Capture and Reporting

          Aboard the Discoverer, NBIS CTD data were collected using a Zenith 
     personal computer equipped with novel CTD acquisition software written by
     Dave Bitterman of AOML.  Both the downcast and upcast were written to hard
     disk.  Syquest tapes held the archived data set.  A color monitor 
     displayed real-time profiles and a real-time listing was produced on an 
     HP lineprinter.  As a backup, the original audio FSK CTD data signal was 
     recorded on video cassette tapes.

          Following each cast at sea, calibrated pressure, temperature, 
     conductivity, and computed CTD salinities marked at the time of bottle 
     closure confirmation were read from the real-time listing and given to 
     the Ocean Chemistry Data Management System (OCDMS) manager.  

     Conductivity Calibration

          The fall EPOCS/TOGA/CO2/JGOFS cruises consisted of 3 legs and 
     31DSEP692/2 was calibrated and processed together with legs 1 and 3.
     Pre-cruise calibrated, 1-db averaged, ASCII CTD data files were received 
     from AOML on 8mm tape in February 21, 1994.  A finalized version of the 
     bottle data base (EQ92FALE.CSV) was released by AOML on February 17, 1994.
     A calibration (.CAL) file was created using the program CALAOML.  CTD 
     and/or bottle data did not exist for casts 1, 7, 16, 22, 25, 34, 39, 48, 
     52, 53, 71, 75, 82, 83, 84, and 120, and these casts were not included 
     in the .CAL file.

          Because the process of how pre-cruise calibration coefficients
     (pressure being nonlinear) and cell corrections were applied to the data
     set, it was decided that CTD and bottle salinities would be fit rather
     than backed out conductivities.  Program LINCALW was modified to read
     and compute a fit to salinities.  Salinity slope (A1) and bias (A0) were 
     applied using CALMSTRW (program descriptions are given below).  Note:

          EP592 consisted of stations  1- 48, CTD casts  1- 53.
	  EP692 consisted of stations 49- 74, CTD casts 54- 84.
	  EP792 consisted of stations 75-107, CTD casts 85-146.
	  AOML CTD #4 was used for stations  1- 66.
	  AOML CTD #1 was used for stations 67-107.

          Fits were computed for the following groups of stations to correct 
     for cast dependent drifts:

     AOML4A consisted of stations 1-22, CTD casts 1-25:
          A0 = -0.1592176E-01
          A1 =  0.1000271E+01
          maximum residual =   0.0156
          standard dev =   0.0056
          70 values discarded from 466 values in 10 repetitions.

     AOML4B consisted of stations 23-48, CTD casts 26-53: (end EP592)
          A0 =  0.1783609E-01
          A1 =  0.9993343E+00
          maximum residual =   0.0182
          standard dev =   0.0067
          59 values discarded from 531 values in 7 repetitions.

     AOML4C consisted of stations 49-67, CTD casts 54-71: (end AOML CTD #4)
          A0 = -0.1083432E+00
          A1 =  0.1003059E+01
          maximum residual  =  -0.0117
          standard dev =   0.0042
          53 values discarded from 404 values in 8 repetitions.

     AOML1A consisted of station 67, CTD casts 72-73: (start AOML CTD #1)
          A0 = -0.2837561E+00
          A1 =  0.1007903E+01
          maximum residual =  -0.0124
          standard dev =   0.0049
	  2 values discarded from 23 values in 3 repetitions.

     AOML1B consisted of stations 68-74, CTD casts 74-84: (end EP692)
          A0 =  0.9982839E-01
          A1 =  0.9972650E+00
          maximum residual =   0.0069
          standard dev =   0.0029
          12 values discarded from 83 values in 6 repetitions.

     AOML1C consisted of stations 75-107, CTD casts 85-146: (end EP792)
          A0 =  0.3461486E-01
          A1 =  0.9990724E+00
          maximum residual =   0.0064
          standard dev =   0.0023
          97 values discarded from 731 values in 8 repetitions.

          A total of 294 values were discarded from 2238; 13% of the fit pairs
     were greater than 2.8 times the standard deviations.  However, all bottle
     data were included in the EPIC (Soreide and Hayes, 1988) .BOT files.  
     Bottles were not shifted around in the .CAL files.  However, the following
     positions were reported to AOML OCDMS manager for consideration as 
     mistrips or samples analyzed out of order:

	  CTD cast   3 bottle position 4.
	  CTD cast  38 bottle positions 5, 6, 7.
	  CTD cast  54 bottle positions 20, 21, 22.
	  CTD cast  57 bottle positions 17 and 18.
	  CTD cast  61 bottle positions 7 and 8.
	  CTD cast  65 bottle positions 3 and 4.
	  CTD cast  80 bottle positions 8 and 9.
	  CTD cast 125 bottle positions 4 and 5.
	  CTD cast 129 bottle positions 6 and 7.
 	  CTD cast 131 bottle positions 4 and 5, 7 and 8.
	  CTD cast 135 bottle positions 6 and 8.
     
     Conductivity Calibration Programs and PPLUS Command (.PPC) Files

          CALAOML creates .CAL raw data file of CTD observations at the time 
            of bottle closures and analyzed water sample values.
          LINCALW reads .CAL raw data file (may be broken into groups), 
            computes a linear least squares fit to CTD-bottle conductivity
            data, applies the model coefficients, discards observations 
            greater than 2.8 times the standard deviation, then refits the
            remaining data.  The process continues until no further 
            observations are rejected.  LINCALW writes .COEF file containing 
            model coefficients and .LOG file.  Water sample conductivity
            is obtained using the FORTRAN routine SAL78 described by Fofonoff
            and Millard (1983).
          CALMSTRW reads .CAL raw data file, applies slope and bias to 
            salinity, and writes .CLB calibrated data file and .SEA calibrated
            data file in WOCE format.
          CALMCONW.PPC (Denbo, 1992) reads .CLB calibrated data file and makes 
            five plots of discrete measurements:  P, T, C, S, and cast number 
            verses CTD-bottle conductivity.  These are examined for cast 
            breaks and drifts in the CTD.
          CALMDEEPW.PPC reads .CLB calibrated data file and makes two plots: 
            CTD salinity and bottle salinity verses potential temperature from
            theta = 0.6 to 2.2 C.

     Temperature Calibration

          Pre-cruise calibrations were the only corrections applied to 
     temperature measurements.  Temperature measurements, calibrations, and 
     computation of derived oceanographic variables used the 1968 temperature 
     scale.  Temperatures were converted to the ITS90 scale for WOCE reporting
     according to:

          T68 = 1.00024 * T90

     as suggested by Saunders (1990):

     Pressure Calibration

          Pre-cruise calibrations were the only corrections applied to
     pressure measurements.

     CTD Data Processing

          Program EPAOML read AOML's 1-db averaged files of pressure,
     temperature, salinity, oxygen current, oxygen temperature, and number
     of scans per bin.  CTD oxygen values were not computed because AOML
     advised that the sensor was bad.  No additional calibrations were
     applied to pressure or temperature.  Salinity slopes and offsets
     computed using LINCALW were applied to salinity.  Final data are in
     EPIC format.

     CTD Data Processing Programs and PPLUS Command (.PPC) Files

          EPAOML reads AOML .AVG file of calibrated P, T, S, OXC, OXT, and 
            bin size.  EPAOML applies a salinity slope and offset, has an 
            option to eliminate 1-point spikes according to the gradients 
            restrictions given in the source code (not used by default), 
            omits additional spikes as specified in the command file, fills 
            data by linear interpolation for a value to exist every whole 
            meter, recomputes conductivity from salinity, and calculates 
            other oceanographic variables.  EPAOML writes the final .CTD data 
            file in EPIC format, and a .LOG file of editted and filled data 
            points.
          EPICBOMSTRW reads .CLB calibrated bottle data file and .CTD EPIC 
            data files (for header information) and writes final .BOT bottle 
            data files in EPIC format.
          DEEPCTD.PPC reads .CTD EPIC pointer file and .BOT EPIC pointer file
            of deep casts only and overplots discrete bottle salinity data on
            the CTD salintiy trace from theta=0.8 to 2.4 C.
          FULLTS.PPC reads .CTD EPIC pointer file and .BOT EPIC pointer file 
	    and overplots bottle and CTD salinity data from theta = 0 to 30 C 
            for each cast.
          TSPLTEP.PPC reads .CTD EPIC pointer file and .BOT EPIC pointer file
            and overplots full water column bottle salinity and CTD trace as 
            well as sigma-t lines for each profile.  TSPLTB.PPC is used to 
            include oxygen data.  
          TEXTNOX reads .CTD EPIC pointer file and writes a PPLUS command
            file containing label commands for table listings of subsampled
            CTD data for each cast to be used with 3PLTNOX.
          3PLTNOX.PPC reads TEXTNOX output and .CTD EPIC pointer file and 
            overplots profiles of temperature, salinity, and sigma-t vs. 
            pressure to 1000 db with subsampled CTD data listed in table form
            for each station.  4PLT1DB.PPC is used to include oxygen data.


     References     

     Denbo, D.W., 1992.  PPLUS Graphics, P.O. Box 4, Sequim, WA, 98382.

     Fofonoff, N.P., and R.C. Millard, Jr., 1983.  Algorithms for Computation 
          of Fundamental Properties of Seawater.  UNESCO Technical Papers in 
          Marine Science 44.

     Saunders, P.M., 1990.  The International Temperature Scale of 1990.  
          ITS90.  WOCE Newsletter, 10, IOS, Wormley, U.K.

     Soreide, N.N., and S.P. Hayes, 1988.  A System for Management, Display,
          and Analysis of Oceanographic Time Series and Hydrographic Data.
          Fourth International Conference on Interactive Information and 
	  Processing Systems for Meteorology, Oceanography, and Hydrology.
  	  American Meteorological Society, Boston, J20-J22.
