R/V Ronald H. Brown METADATA - 1998

Class of Data: Surface ocean and atmospheric carbon dioxide
concentrations

Dataset Identifier: R/V Ronald H. Brown

One File: RHB1998

Statement of how to cite dataset:

Ron Brown website: http://www.aoml.noaa.gov/ocd/gcc/rvbrown_data1998.php

These data are made freely available to the public and the scientific
community

in the belief that their wide dissemination will lead to greater
understanding

and new scientific insights. The availability of these data does not

constitute publication of the data. We rely on the ethics and integrity
of

the user to assure that AOML receives fair credit for our work. Please
send

manuscripts using this data to AOML for review before they are submitted

for publication so we can insure that the quality and limitations of the
data

are accurately represented.

Measurement platform identifier: NOAA research vessel Ronald H. Brown
(R104)

Cruise Information:

The Ron Brown conducted 4 major cruises in the north Atlantic and
eastern Pacific for a total of 12 legs. Also included are data from 2
transit legs from the Atlantic to the Pacific.

Project Information:

The system was operated by personnel from AOML or PMEL (Pacific Marine
Environmental Laboratory). The work was sponsored by the Underway pCO2
on Ships project of the NOAA climate program.

Scientist responsible for technical quality of dataset:

Rik Wanninkhof

NOAA/AOML/Ocean Chemistry Division

4301 Rickenbacker Causeway

Miami, Florida 33149

Rik.Wanninkhof@noaa.gov

Contact person for this dataset:

Bob Castle

NOAA/AOML/Ocean Chemistry Division

4301 Rickenbacker Causeway

Miami, Florida 33149

Robert.Castle@noaa.gov

Timestamp for initial submission of dataset: 09/03/08

Timestamp for the most recent update of dataset: 09/03/08

Timestamp period the dataset refers to: 1/8/1998 -- 11/22/1998

Geographic area the dataset refers to:

10 S to 51 N

146 W to 10 W

1998 Cruises:

RB199801 -- 24 North Leg 1

Miami, FL to Las Palmas, Canary Islands

January 8, 1998 to January 21, 1998

Chief Scientist -- Gregg Thomas

Operator -- Dana Greeley

RB199802 - 24 North Leg 2

Las Palmas, Canary Islands to Miami, FL

January 23, 1998 to February 24, 1998

Chief Scientist -- Kitack Lee

Operator -- Dana Greeley

RB199803 - Gasex98 Leg 1

Miami, FL to Lisbon, Portugal

May 11, 1998 to May 19, 1998

Chief Scientist -- Jim Butler

Operator -- Bob Castle

RB199804 - Gasex98 Leg 2

Lisbon, Portugal to Punta del Gado, Azores Islands

May 25, 1998 to June 26, 1998

Chief Scientist -- Rik Wanninkhof

Operator -- Bob Castle

RB199805 - Gasex98 Leg 3

Punta del Gado, Azores Islands to Miami, FL

June 28, 1998 to July 7, 1998

Chief Scientist -- Shari Yvon-Lewis

Operator -- Craig Neill

RB199806 - Transit98 Leg 1

Miami, FL to Panama Canal

July 12, 1998 to July 16, 1998

Chief Scientist -- None

Operator -- Jason Masters

RB199807 - Transit98 Leg 2

Panama Canal to Newport, OR

July 16, 1998 to July 27, 1998

Chief Scientist -- None

Operator -- Jason Masters

RB199808 - Vents98 Leg 1

Newport, OR to Victoria, BC, Canada

July 30, 1998 to August 15, 1998

Chief Scientist -- Ed Baker

Operator -- Dana Greeley

RB199810 - Vents98 Leg 3

Newport, OR to Victoria, BC, Canada

August 24, 1998 to September 20, 1998

Chief Scientist -- Bob Embley

Operator -- Jim Gendron

RB199811 - Vents98 Leg 4

Victoria, BC, Canada to Seattle, WA

September 23, 1998 to October 3, 1998

Chief Scientist -- Hugh Milburn

Operator -- Marilyn Roberts

RB199812 - TAO98 Leg 2

Seattle, WA to Panama Canal

October 15, 1998 to November 14, 1998

Chief Scientist -- John Shanley

Operator -- Esa Peltola

RB199813 - TAO98 Leg 2

Panama Canal to Charleston, SC

November 17, 1998 to November 22, 1998

Chief Scientist -- None

Operator -- Esa Peltola

List of variables included in this dataset:

COLUMN HEADER EXPLANATION

1\. GROUP/SHIP: AOML_Brown for all underway data from the Ron Brown.

2\. CRUISE_DESIGNATION: Cruise ID (e.g., RBYYYYnn where RB = Ron Brown,
YYYY

= the four digit year, and nn = the cruise number for

that year).

3\. JD_GMT: Decimal year day.

4\. DATE_DDMMYYYY: GMT date. The date format has been changed to comply

with the IOCCP recommendations.

5\. TIME_HH:MM:SS: GMT time.

6\. LAT_DEC_DEGREE: Latitude in decimal degrees (negative values are in
the southern hemisphere).

7\. LONG_DEC_DEGREE: Longitude in decimal degrees (negative values are
in the western hemisphere).

8\. xCO2W_PPM: Mole fraction of CO2 (dry) in the equilibrator

headspace at equilibrator temperature (Teq) in parts

per million.

9\. xCO2A_PPM: Mole fraction of CO2 in air in parts per million.

10\. EqTEMP_C: Temperature in equilibrator water in degrees

centigade. Temperature in equilibrator measured with

a calibrated thermistor.

11\. PRES_EQUIL_hPa: Barometric pressure in the lab in hectopascals (1

hectopascal = 1 millibar).

12\. SST(TSG)\_C: Temperature from the ship\'s thermosalinograph in

degrees centigrade.

13\. SAL(TSG)\_PERMIL: Salinity from the ship\'s thermosalinograph on
the

Practical Salinity Scale.

14\. fCO2w,eq: Fugacity of CO2 in the equilibrator in

microatmospheres calculated as outlined below.

15\. fCO2W@SST_uatm: Fugacity of CO2 in sea water in microatmospheres

calculated as outlined below.

16\. fCO2A_uATM: Fugacity of CO2 in air in microatmospheres

calculated as outlined below.

17\. dfCO2_uatm: Sea water fCO2 - air fCO2 in microatmospheres. This

uses the average air value for the current hour.

The following fields have been QC\'ed by the CO2 group:

GROUP/SHIP

CRUISE_DESIGNATION

JD_GMT

DATE_DDMMYYYY

TIME_HH:MM:SS

LAT_DEC_DEGREE

LONG_DEC_DEGREE

xCO2W_PPM

xCO2A_PPM

EqTEMP_C

PRES_EQUIL_hPa

fCO2w,eq

fCO2W@SST_uatm

fCO2A_uATM

dfCO2_uatm

The following fields are from the ship\'s onboard systems and the
quality of this

data cannot be verified:

SST(TSG)\_C

Sal(TSG)\_Permil

Narrative description of system design:

CO2 ANALYTICAL SYSTEM:

The concentration of carbon dioxide (CO2) in surface ocean water is
determined

by measuring the concentration of CO2 in gas that is in contact with the
water.

Surface water is pumped \~ 100 m through 7/8\" Teflon tubing from an
inlet

in the ship\'s bow to the equilibration chamber. Water comes from the
bow

intake \~4.2 m below the water line and the TSG is located close to the
inlet.

When the SST is below about 20 ^o^C, friction in the pipes and from the
pump cause

heating and the Teq is higher than SST. When the SST is higher than
about 25 ^o^C,

the ship's air conditioning cools the water and the Teq is lower than
SST.

The equilibration chamber has an enclosed volume of gas, or headspace,
and a pool

of seawater that continuously overflows to a drain. As the water flows
through the

chamber, the dissolved gases (like CO2) partition between the water and
the

headspace. At equilibrium, the ratio of CO2 in the water and in the
headspace is

influenced most by temperature, and that relationship is known. By
measuring

the concentration of CO2 in the headspace and the temperature in the
chamber,

the partial pressure (or fugacity) of CO2 in the surface water can be
calculated.

INSTRUMENT DESCRIPTION

The general principle of instrumental design can be found in Wanninkhof
and Thoning

(1993), Ho et al. (1995), and Feely et al. (1998). The concentration of
CO2 in the

headspace gas is measured using the adsorption of infrared (IR)
radiation, which

results from changes in the rotational and vibrational energy state of
the CO2

molecule. The LI-COR detector passes IR radiation through two 6\" cells.
The

reference cell is flushed with a gas of known CO2 concentration. The
sample cell

is flushed with the headspace gas. A vacuum-sealed, heated filament is
the

broadband IR source. The IR radiation alternates between the two cells
via a

chopping shutter disc. An optical filter selects an adsorption band
specific

for CO2 (4.26 micron) to reach the detector. The solid state (lead
selenide)

detector is kept at -12 degrees °C for excellent stability and low
signal

noise (less than 0.2 ppm).

Several steps are taken to reduce interferences and to increase the
accuracy

of the measurements. After the equilibration chamber, the headspace
travels

through a drying trap to remove water vapor. During each analysis, the

headspace gas is compared to a reference gas of known concentration. To

improve the accuracy of the measurements, three different gaseous
standards

for CO2 are analyzed once an hour instead of the headspace gas.

Analyzer: LI-COR 6251 (analog output) infrared (IR) analyzer.

Method of Analysis: Differential analyses relative to the low standard.
Measures

dried equilibrator headspace gas. Gas flow is stopped prior to IR
readings.

Drying Method: The equilibrator headspace sample gas first goes through
a glass

condenser cooled to \~ 5 ^o^C. The sample and standard gases pass
through a short

column of magnesium perchlorate before reaching the analyzer.

Equilibrator (setup, size, flows): The equilibrator is based on a design
by R.

Weiss and was fabricated from a plexiglass housing with \~8 L water
reservoir and

\~16 L gaseous headspace. Water flow rate is \~11 L/min. Headspace
recirculation

rate is \~200 ml/min.

Additional sensors:

Thermistor mounted in the bottom of the equilibrator.

Setra Barometer Model 370

YSI Model 600R thermosalinograph with temperature, salinity, and
dissolved

oxygen sensors. This TSG is mounted in the Hydro lab sink near the

equilibrator and the two are teed off the uncontaminated seawater feed.

The dissolved oxygen measurements are not reported in the final data
file.

Narrative statement identifying measurement method for each required
parameter:

CALCULATIONS:

The mixing ratios of ambient air and equilibrated headspace air are
calculated

by fitting a second-order polynomial through the hourly averaged
millivolt

response of the detector versus mixing ratios of the standards. Mixing
ratios

of dried equilibrated headspace and air are converted to fugacity of CO2
in

surface seawater and water saturated air in order to determine the fCO2.

For ambient air and equilibrator headspace, the fCO2a (or fCO2eq) is
calculated

assuming 100% water vapor content:

fCO2eq = xCO2eq(P-pH2O)exp(B11+2\*d12)P/RT

where fCO2eq is the fugacity in the equilibrator, pH2O is the water
vapor

pressure at the sea surface temperature, P is the atmospheric pressure
(in atm),

T is the SST or equilibrator temperature (in K) and R is the ideal gas
constant

(82.057 cm\^3·atm·deg\^-1·mol\^-1). The exponential term is the fugacity
correction

where B11 is the second virial coefficient of pure CO2

B11 = -1636.75 + 12.0408T - 0.032795T\^2 + 3.16528E-5 T\^3

and d12 = 57.7 - 0.118 T is the correction for an air-CO2 mixture in
units of

cm\^3·mol\^-1 (Weiss, 1974).

The calculation for the fugacity at SST involves a temperature
correction term

for the increase of fCO2 due to heating of the water from passing
through the

pump and through 5 cm ID PVC tubing within the ship. The empirical
temperature

correction from equilibrator temperature to SST is:

fCO2(SST) = fCO2(eq) /

Exp ((Teq-SST) \* \[0.03107 -- 2.7851E-4 \* Teq -- 1.8391E-3 \*
ln(fco2eq \* 1.0E-6)\])

where SST is sea surface temperature and Teq is the equilibrator
temperature in

degrees °C.

Sampling Cycle:

The system runs on an hourly cycle during which 3 standard gases, 3 air

samples from the bow tower and 8 surface water samples (from the

equilibrator head space) are analyzed on the following schedule:

Mins. after hour Sample

4 Low Standard

8 Mid Standard

12 High Standard

16.5 Water

21 Water

25.5 Water

30 Water

34 Air

38 Air

42 Air

46.5 Water

51 Water

55.5 Water

60 Water

NOTES ON DATA:

Columns have a default value of --999.99 in case of instrument
malfunction,

erroneous readings or missing data. Furthermore, if a suspicious xCO2
value,

pressure or temperature value is encountered, the fCO2 is not
calculated.

Analytical Instrument Manufacturer/Model:

The Ron Brown system (version 2.5) was an in-house prototype built by
Jason

Masters, Mike Shoemaker, and Bob Castle in 1998. The analyzer is a
LI-COR 6251

(analog output) infrared analyzer.

Standard Gases and Reference Gas: The three standard gases came from
CMDL

in Boulder and are directly traceable to the WMO scale. While individual
data

points above the high standard gas concentration or below the low
standard gas

concentration may not be accurate, the general trends should be
indicative of the

seawater chemistry.

Description of any additional environmental control:

The system is located in the Hydro Lab of the Ron Brown. The room is

air-conditioned with little temperature fluctuation.

Resolution of measurement:

The resolution of the instrument is better than 0.1 ppm.

Estimated overall uncertainty of measurement:

The xCO2eq measurements are believed accurate to 0.1 ppm. The

fCO2@SST measurements are believed to be precise to 0.2 ppm.

List of calibration gases used:

The standards used during the 1998 field season were:

STANDARD TANK \# CONCENTRATION VENDOR

Low CC114999 275.63 CMDL

Low CA03372 283.26 CMDL

Low,Mid CC117904 297.74 CMDL

Low CA01208 299.06 CMDL

Mid CA02032 341.14 CMDL

Low,Mid,High CC106641 360.62 CMDL

Mid,High CC111795 408.35 CMDL

High CA03065 523.44 CMDL

Traceability to an internationally recognized scale (including
date/place of last calibration made):

All standards are obtained from NOAA/CMDL, now called the Global

Monitoring Division of the Earth Research Laboratory and are directly

traceable to WHO scale.

Uncertainty of assigned value of each calibration gas:

The uncertainty based on pre and post cruise calibrations is less

than 0.05 ppm.

Pressure/Temperature/Salinity:

For information about the ship's thermosalinograph, contact Chief Survey
Tech

Jonathan Shannahoff at jonathan.shannahoff@noaa.gov.

Units:

All xCO2 values are reported in parts per million (ppm) and fCO2 values

are reported in microatmospheres (uatm) assuming 100% humidity at the

equilibrator temperature.

Bibliography:

DOE (1994). Handbook of methods for the analysis of the various
parameters of the

carbon dioxide system in sea water; version 2. DOE.

Feely, R. A., R. Wanninkhof, H. B. Milburn, C. E. Cosca, M. Stapp and P.
P. Murphy

(1998). A new automated underway system for making high precision pCO2

measurements onboard research ships. Analytica Chim. Acta 377: 185-191.

Ho, D. T., R. Wanninkhof, J. Masters, R. A. Feely and C. E. Cosca
(1997).

Measurement of underway fCO2 in the Eastern Equatorial Pacific on NOAA

ships BALDRIGE and DISCOVERER, NOAA data report ERL AOML-30, 52 pp.,

NTIS Springfield.

Wanninkhof, R. and K. Thoning (1993). Measurement of fugacity of CO2 in
surface

water using continuous and discrete sampling methods. Mar. Chem.
44(2-4):

189-205.

Weiss, R. F. (1970). The solubility of nitrogen, oxygen and argon in
water and

seawater. Deep-Sea Research 17: 721-735.

Weiss, R. F. (1974). Carbon dioxide in water and seawater: the
solubility of

a non-ideal gas. Mar. Chem. 2: 203-215.

Weiss, R. F., R. A. Jahnke and C. D. Keeling (1982). Seasonal effects of

temperature and salinity on the partial pressure of CO2 in seawater.

Nature 300: 511-513.

Comments related to all 1998 data:

1\. xCO2 values outside the range of the standard gases (i.e. below the
low standard or above the high standard) are not as accurate as values
within the range. However, the general trends should be indicative of
the seawater chemistry.

2\. Data from the ship's computer system (SST and salinity) were merged
into the underway system's data file with an approximate 3 minute delay
factor. This is to account for the time it takes for sea water to travel
from the bow intake to the equilibrator in the Hydro Lab.

3\. Prior to this cruise, the operation of the Valco multi-port valve
was changed in an attempt to reduce the number of mistrips that had been
occurring about 1.5% of the time. Previously, the Valco reset to the
home position after each measurement and then stepped to the correct
position. For this cruise, the Valco was set to the following
configuration:

Position 1 Water

Position 2 Air

Position 3 Water

Position 4 Std 1 (low)

Position 5 Std 2 (mid)

Position 6 Std 3 (high)

The valve was then stepped only at the end of each phase, or 6 times per
hour. While this reduced the number of mistrips, the result when the
valve failed to trip was that the valve would be in the wrong position
for every succeeding phase until it was reset after the Std 3 phase.

4\. Fluorometer data was added to the feed from the ship\'s computer
system before the start of this cruise.

5\. A separate power supply was added to the system to drive the
equilibrator thermistor. The thermistor was recalibrated and a new
equation for converting voltage to temperature was added to the program.
Mercury thermometer measurements taken during the first cruise verify
that the new equation is accurate.

Comments related to the individual legs:

RB199801: 1. The standard gases used on this leg were: low, 297.74 ppm;
mid, 341.14 ppm; and high, 408.35 ppm.

2\. There were 9 mistrips of the Valco valve resulting in 183 lost data
measurements. When mistrips occur, low standard gas flows during the mid
standard phase and mid standard gas flows during the high standard
phase. To correct this, the low and mid standard voltage responses are
moved to the appropriate positions and the high standard response is
taken as the average of the previous and next hour's response.

RB199802: 1. The standard gases used on this leg were: low, 297.74 ppm;
mid, 341.14 ppm; and high, 408.35 ppm.

2\. There were 33 mistrips resulting in 183 lost data measurements.
Standard gas responses were corrected as in RB199801.

RB199803: 1. The standard gases used on this leg were: low, 297.74 ppm;
mid, 360.62 ppm; and high, 408.35 ppm.

2\. There were 8 mistrips resulting in 25 lost data measurements.
Standard gas responses were corrected as in RB199801.

3\. The system was down at the beginning of the leg while the program
was modified to accept a new feed from the ship\'s computer system
(SCS). It was started on May 10 at midnight.

4\. The system was down on May 16 for 1-1/2 hours to recalibrate the YSI
TSG.

5\. The ship\'s salinity sensor began giving bad readings on May 16 at
1645 GMT. I used the good salinity values (prior to May 16) to derive a
linear relationship between the SCS salinity and the YSI salinity.
Starting on May 16 at 1959 SCS salinity readings were replaced with
computed salinity using the equation SCS salinity = YSI salinity \*
0.7656 + 8.336.

6\. Also on May 16, we discovered a leak in the hose supplying
uncontaminated sea water to the equilibrator which was allowing ambient
lab air to get into the equilibrator. For this reason, there is more
variability than normal in the fCO2 values for this leg.

7\. Some fCO2 values must be considered questionable due to sharp
changes in the fCO2 level. They were not removed from the data set
because no definitive reason to consider them bad could be found. They
are listed below:

Date Time Year day

5/13 1120 133.4728

5/14 1229 134.5207

5/15 1159 135.4998

5/15 1646 135.6988

5/15 1716 135.7197

5/15 1730 135.7290

5/18 1955 138.8300

RB199804: 1. The standard gases used on this leg were: low, 275.63 ppm;
mid, 297.74 ppm; and high, 360.62 ppm.

2\. There were 12 mistrips resulting in 22 lost data measurements.
Standard gas responses were corrected as in RB199801.

3\. On May 29 some small air leaks in the system were discovered and
repaired. Data prior to 2030 GMT shows higher variability than normal.

4\. On May 30 from 2330 to 2400 GMT positive pressure in equilibrator
caused headspace gas to back up into the Licor sample cell, resulting in
bad readings.

5\. On May 31 from 2115 to 2300 GMT the system was down to install a
solenoid valve on the sample output of the Licor.

6\. On June 3 from 1412 to 1825 the system was down to recalibrate the
YSI TSG.

7\. On June 9 from 545 to 625 the system was down to clean the
equilibrator\'s shower head.

8\. On June 12 from 1225 to 1312 the system was down to install a
bounceless switch on the Valco valve.

9\. On June 12 from 1430 to 1600 the system was down to recalibrate the
YSI O2 sensor.

10\. On June 17 from 1505 to 1930 the system was down to recalibrate the
YSI O2 sensor.

11\. On June 25 from 1315 to 1640 the system hung due to operator error.

RB199805: 1. The standard gases used on this leg were: low, 275.63 ppm;
mid, 297.74 ppm; and high, 360.62 ppm. On July 5 at 1545 they were
changed to 297.74, 360.62, and 408.35 respectively due to higher water
values.

2\. Gas flow in the water phase was low (but adequate) until June 30 @
1100 GMT.

3\. On July 3 from 0230 to 0330 the system was down due to a power
failure.

RB199806: 1. The standard gases used on this leg were: low, 299.06 ppm;
mid, 360.62 ppm; and high, 408.35 ppm.

2\. The YSI TSG suffered from an apparent low water flow condition for
this entire leg. Salinity values begin to degrade noticeably on YD
195.25 and temperature before that.

3\. SCS salinity and temperature data was bad until YD 193.553
approximately the first 13 hours). I did a linear fit of equilibrator
temperature to SCS temperature readings and derived SST by the following
equation: SST = (EqT \* 1.009079) - 0.331455 with R\^2 = 0.989783. For
SSS I did an eyeball check of YSI salinity vs SCS salinity for the
period from 193.6 to 195 when there was a near constant offset between
the two. I then replaced the SCS salinities up to YD 193.553 with
computed salinities using the formula SSS = YSI sal - 0.07.

4\. The Air Cadet that pumps air from the bow tower to the system went
bad on YD 194.3 and was repaired on 195.7. In most cases I used the last
of 3 air measurements during this time period.

5\. Latitude and longitude values were recorded by the system with only
3 places of precision (e.g. -80.1, 9.97, etc). I merged SCS data
provided by the ship into the data file to obtain better values.

RB199807: 1. The standard gases used on this leg were: low, 299.06 ppm;
mid, 360.62 ppm; and high, 408.35 ppm. On July 23 at 0300 the high
standard was changed to 523.44 ppm because of high xCO2 values in the
surface water. At 0400 the mid standard was changed to 408.35 ppm. At
0200 the low standard was changed to 360.62 ppm. On July 24 at 1000 the
standards were changed back to their original configuration.

2\. For the last day of this leg (nearing Newport) large variations in
surface water xCO2 values were observed. I left these in the data file
because of simultaneous large changes in SST and SSS.

3\. Latitude and longitude values were recorded by the system with only
3 places of precision (e.g. -80.1, 9.97, etc). I merged SCS data
provided by the ship into the data file to obtain better values.

RB199808: 1. The standard gases used on this leg were: low, 299.06 ppm;
mid, 360.62 ppm; and high, 408.35 ppm.

2\. For the first four hours low gas flow in the high standard phase
(std 3) resulted in slightly depressed voltage readings due to
inadequate flushing of the Licor\'s sample cell. Since the voltages in
both air and water phases were at most only slightly higher than the mid
standard gas, I have retained all of the original values without
applying a correction.

3\. On August 9 from 0030 through 0430, the ship conducted towing
operations that caused stack gas to enter the intake during the air
phase. All air values for this period have been removed.

4\. The feed from the ship\'s computer system (SCS) gave only 3
significant digits in latitude and longitude for the first 224 rows in
the data file.I \'fixed\' this by interpolating values in both the
latitude and longitude columns. This should be a fairly close
approximation to the actual cruisetrack. If I can locate the original
data from the ship, I will replace the interpolated values with the
actual ones.

RB199810: 1. The standard gases used on this leg were: low, 299.06 ppm;
mid, 360.62 ppm; and high, 408.35 ppm. On September 17 at 1700, the low
standard was changed to 283.26 because the original tank was nearing
empty.

2\. The ship\'s salinity sensor began giving erratic readings starting
on day 256 and continuing to the end of the cruise. I replaced these
values (from year day 255.75 to the end) with salinity values I derived
from the YSI salinity sensor attached to the system. I used data from
the beginning of the cruise to day 255.75 to come up with a linear
equation relating the two. The equation used was: SCS salinity =
0.907480 \* YSI salinity + 2.861642 with R\^2 = 0.910347.

3\. The computer crashed on day 258.642 and the system was down for
eight hours (until 258.972).

4\. The feed from the ship\'s computer system (SCS) gave only 3
significant digits in latitude and longitude for the first 1114 rows in
the data file. I \'fixed\' this by interpolating values in both the
latitude and longitude columns. This should be a fairly close
approximation to the actual cruise track. If I can locate the original
data from the ship, I will replace the interpolated values with the
actual ones.

RB199811: 1. The standard gases used on this leg were: low, 283.26 ppm;
mid, 360.62 ppm; and high, 408.35 ppm.

2\. The ship\'s salinity sensor began giving erratic readings near the
end of the previous leg. By the end of leg 3, the readings settled down.
However, the offset between the YSI TSG attached to our system and the
ship\'s TSG changed. For most of leg 3 the YSI gave readings about 0.15
higher than the ship\'s TSG. From near the end of leg 3 and for all of
leg 4, the YSI read about 0.07 lower than the ship\'s TSG. I have left
the ship\'s salinity values as they were recorded and used them to
compute fCO2, etc for this leg.

3\. Problems with the PC clock and the feed from the ship\'s computer
system resulted in the loss of about 2-1/2 hour\'s worth of data at the
beginning of leg 4 (from 267.014 through 267.109).

4\. Starting on Oct. 1 the lat and lon from the ship\'s computer system
included only 3 significant digits. I fixed this by interpolating
latitude and longitude values.

RB199812: 1. The standard gases used on this leg were: low, 283.26 ppm;
mid, 360.62 ppm; and high, 408.35 ppm. On November 1 at 1700 the
standards were changed to 360.62, 408.35, and 523.44 respectively due to
high xCO2 values in the surface water. On November 8 at 2000 they were
changed back to their original configuration.

2\. Immediately after the first change, a drop in atmospheric CO2 levels
of approximately 1 ppm was observed. Air values gradually increased over
the next few days until they were consistent with values observed before
the tank change. I believe this was due to incomplete flushing of the
regulator after changing tanks.

3\. The Licor IR analyzer failed at the start of the cruise and was
replaced with the spare. The first 26 hours of data were removed. All
data in the file are from the replacement (good) Licor.

RB199813: 1. The standard gases used on this leg were: low, 283.26 ppm;
mid, 360.62 ppm; and high, 408.35 ppm.

2\. On November 21 at 0000 GMT, the ship\'s computer system was shut
down for software work. For the remainder of the leg, I derived SST and
salinity from the equilibrator temperature and the YSI salinity
respectively. The equation used for temperature was SST = EqT \*
1.016550 - 0.618679 with R\^2 = 0.996014. The equation used for salinity
was SSS = YSI salinity \* 0.849961 + 5.162161 with R\^2 = 0.942750.

3\. Heightened pCO2 air levels were observed when rounding the western
tip of Cuba and when steaming up the east coast of the United States. I
believe these were not caused by stack gases and have left them in the
data set.