README FOR Ronald H. Brown UNDERWAY fCO2 FILES 
 
The electronic data in comma delimited ASCII form (.CSV) can be found at:
http://www.aoml.noaa.gov/ocd/gcc/rvbrown_introduction.php



For further information or special requests regarding data format contact:
	Mr. Bob Castle
	Atlantic Oceanographic and Meteorological Lab
	4301 Rickenbacker Causeway
	Miami, FL 33149
	
	email: robert.castle@noaa.gov
	Phone: 305-361-4418

****************** Use of AOML CO2 Underway Data **************************
* [Adapted from NOAA Climate Monitoring and Diagnostics Laboratory (CMDL) *
************* Carbon Cycle Greenhouse Gasses (CCGG) web site] *************

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.

*********************** Reciprocity Agreement *****************************
* [Adapted from NOAA Climate Monitoring and Diagnostics Laboratory (CMDL) *
************* Carbon Cycle Greenhouse Gasses (CCGG) web site] *************

Use of these data implies an agreement to reciprocate.  Laboratories making
similar measurements agree to make their own data available to the general
public and to the scientific community in an equally complete and easily 
accessible form.  Modelers are encouraged to make available to the community, 
upon request, their own tools used in the interpretation of the AOML data,
namely well documented model code and any additional information necessary for 
other scientists to repeat the work and to run modified versions.


***************************************************************************
							Web Site Changes
							  April, 2004

	Our web site for underway pCO2 data from the NOAA ship Ronald H. Brown
has undergone a facelift and now has a new address: 

http://www.aoml.noaa.gov/ocd/gcc/rvbrown_introduction.php.  

The data for each year can now be accessed from a drop-down list box on this 
page.  Cruise tracks are now color coded to show the approximate partial pressure 
of CO2 in surface water over the ship's course.  Master maps of cruise tracks for
a four year period are now at: 

http://www.aoml.noaa.gov/ocd/gcc/rvbrown_cruisetracks.php.

	In addition to these cosmetic changes, cruise data files now have a new
format that includes auxilliary meteorological, oceanographic and ship's
navigation data.  These changes have been made to conform with the
recommendations of the International Ocean Carbon Coordination Project 
(http://ioc.unesco.org/ioccp).  The purpose of this project is to standardize
measurement techniques and QA/QC procedures, coordinate international ocean 
carbon observations, and improve accessibility to carbon data sets in order
to better meet the needs of the research community.

	For the most part, changes to the data files consist of new field headers
and new fields.  One field, the "Date" field, has been changed to a new format.
Additional data fields include fluorometer data, wind speed and direction, sea
level pressure, ship speed and course, air temperature, QC flags, and diagnostics.
Beginning with the first cruise of 2004, all new data fields will be present in 
the data files.  Data files from 2003 have all the new fields except for air
temperature, ship's speed and ship's course.  Older data files will be updated to 
the new format in the future.  In cases where the data are not available for a 
particular field, the column will appear with values of -9 in each record.  Most 
of the additional data is taken from the ship's computer system "as is" with no 
quality control checking.  All wind speeds and directions, fluorometer readings, 
outside air temperature and pressure, and ship's speed and course have not been 
quality controlled and should only be used with that limitation in mind.  To get
quality controlled meteorological from the Ron Brown, visit the Center for 
Ocean-Atmosphere Prediction Studies web site at:
http://www.coaps.fsu.edu/RVSMDC/cgi-bin/nonwoce-ship.cgi?id=WTEC
The following list gives the new data fields with units and notes about changes in 
format.

1.	GROUP/SHIP:	AOML_Brown for all Ron Brown data (NEW).
2.	CRUISE_DESIGNATION:	RBYYYYNN.  All Ron Brown data will give the cruise designation
	RB followed by the 4-digit year and the 2-digit cruise number (NEW).
3.	JD_GMT:	Decimal year day (same as in old files).
4.	DATE_DDMMYYYY:	The date format has been changed to comply with the IOCCP 
	recommendations (CHANGED).
5.	TIME_HH:MM:SS:	GMT time (same as in old files).
6.	LAT_DEC_DEGREE:	Latitude in decimal degrees (negative values are in southern
	hemisphere).
7.	LONG_DEC_DEGREE:	Longitude in decimal degrees (negative values are in western
	hemisphere).
8.	xCO2W_PPM:	Mole fraction of CO2 in the equilibrator at equilibrator temperature
	(Teq) in parts per million.
9.	xCO2A_PPM:	Mole fraction of CO2 in air in parts per million.
10.	PRES_EQUIL_hPa:	Barometric pressure in the lab in hectopascals [1 hectopascal = 
	1 millibar].
11.	PRES_SEALEVEL_hPa:	Barometric pressure from ship's computer system, corrected to
	sea level in hectopascals [1 hectopascal = 1 millibar] (NEW).
12.	EqTEMP_C:	Temperature in equilibrator water in degrees centrigade.
13.	SST(TSG)_C:	Temperature from the ship's thermosalinograph in degrees centrigrade.
14.	SAL(TSG)_PERMIL:	Salinity from the ship's thermosalinograph in [Practical 
	Salinity Scale].
15.	WATER_FLOW_L/MIN:	Water flow through equilibrator in liters per minute (NEW).
16.	GAS_FLOW_IR_ML/MIN:	Gas flow through the Licor infrared analyzer before the flow
	is stopped in milliliters per minute (NEW).
17.	TEMP_IR_C:	Temperature of the Licor infrared analyzer sample cell in degrees
	centrigrade (NEW).
18.	PRES_IR_hPa:	Pressure in the Licor infrared analyzer in hectopascals.  NOTE:
	There is no pressure sensor in the Licor but since it is vented to atmosphere
	prior to measurement, this value is the same as number 10 above.
	[1 hectopascal = 1 millibar](NEW).
19.	SHIP_HEADING_TRUE_DEGREE:	Ship's heading from ship's computer system in degrees 
	with 0 = North and 90 = East (NEW).
20.	SHIP_SPEED_KNOT:	Ship's speed from ship's computer system in knots (NEW).
21.	WIND_DIR_REL_DEGREE:	Wind direction relative to the ship from ship's computer
	system in degrees with 0 = from the bow and 90 = from starboard (NEW).
22.	WIND_SPEED_REL_M/S:	Wind speed relative to the ship from ship's computer system in
	meters per second (NEW).
23.	fCO2W@SST_uATM:	Fugacity of CO2 in sea water in microatmospheres.
24.	QC_FLAG_WATER:	Quality control flag for sea water xCO2 and fCO2 values with 2 =
	good value, 3 = questionable value, 4 = bad value, and 9 = no measurement taken (NEW).
25.	fCO2A_uATM:	Fugacity of CO2 in air in microatmospheres.
26.	QC_FLAG_AIR:	Quality control flag for air xCO2 and fCO2 with 2 = good value,
	3 = questionable value, 4 = bad value, and 9 = no measurement taken (NEW).
27.	dfCO2_uATM:	Sea water fCO2 - air fCO2 in microatmospheres.  This uses the average air
	value for the current hour.
28.	FLUORO_uG/L:	Reading from the Turner 10-AU fluorometer in micrograms per liter 
	(NEW).
29.	WIND_SPEED_TRUE_M/S:	True wind speed in meters per second (NEW).
30.	WIND_DIR_TRUE_DEGREE:	True wind direction in degrees where 0 = North and 90 = East
	(NEW).
31.	AIR_TEMP_C:	Outside air temperature from ship's computer system in degrees 
	centrigrade	(NEW).


*********************************************************************************
February, 2004

The YSI thermosalinograph was replaced with an SBE micro TSG from Seabird that includes
temperature and conductivity sensors.  The data from this unit is only used for quality 
control checks and is not included in the final data file.  It can be obtained from Bob 
Castle (robert.castle@noaa.gov) if necessary.


*********************************************************************************
September, 1997

FILE FORMAT

Column 			Explanation
JD				Julian Day
Date		    Date  (month, day, year)
Time		 	Greenwich Mean Time
Lat				Latitude (decimal degrees)
Long			Longitude (decimal degrees)
xCO2,w			Mixing ratio of CO2 (dry) in headspace of equilibrator.
                    	Water comes from a bow intake 5 m below the water line (in ppm)
xCO2,a			Mixing ratio of CO2 (dry) from the bow of the ship (15 m above water)
EqTemp			Temperature in equilibrator measured with a calibrated thermistor
                     	(in degrees C)
Pressure		Pressure in laboratory (in mB)
SST(TSG)		Sea surface temperature measured at the water intake 5 m below the 
						water line (in degrees C)
Sal(TSG)		Salinity measured at the water intake (5 m below water line)
fCO2w,eq		Fugacity of water in equilibrator calculated according to DOE (1994) 
				in microatmospheres)
fCO2w,in situ	Fugacity of water at SST calculated from algorithm of Weiss et al. (1982)
fCO2a 			Fugacity of CO2 in air
dfCO2 			Water-air fugacity difference




CALCULATIONS:

The mixing ratios of ambient air and equilibrated headspace air are calculated by fitting a 
second-order polynomial through the hourly averaged 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:

	fCO2a/eq = xCO2a/eq(P-pH2O)exp(B11+2d12)P/RT

				
where fCO2a/eq is the fugacity in ambient air or 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^3atmdeg^-1mol^-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^3mol^-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 water in the equilibrator is typically 0.2 C 
warmer than sea surface temperature. The empirical temperature correction from 
equilibrator temperature to SST is outlined in Weiss et al. (1982).

	dln(fCO2)=(teq-SST)(0.0317-2.7851E-4 teq - 1.839E-3 ln(fCO2eq))


where dln(fCO2)  is the difference between the natural logarithm of the fugacity at teq 
and SST, and teq is the equilibrator temperature in degrees C.


NOTES ON DATA:
Columns have a default value of -999.99 in case of instrument malfunction or erroneous 
readings.  Furthermore, if a suspicious xCO2 value, pressure or temperature value is 
encountered which cannot be readily extrapolated, the fCO2 is not 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 analyses are done with an infrared 
analyzer calibrated with three standard gases spanning the anticipated range of water and 
air values.  The standard gases come from NOAA/CMDL in Boulder and are directly traceable 
to the WMO scale.

The system also includes a YSI thermosalinograph (TSG) that contains temperature, salinity, 
and dissolved oxygen sensors.  The uncontaminated sea water line is teed off with one pipe 
going to the equilibrator and the other going to the YSI.  Data from the YSI is logged by 
the program to the raw data file but is not included in the final data file.  In addition, 
a feed from the ship's computer system provides the program with date, time, latitude, 
longitude, SST, and salinity.  This data feed has been expanded over the years to include 
wind speed and direction (both absolute and relative) and data from the ship's underway 
fluorometer.  These additional parameters are logged to the raw data file but do not appear 
in the final data file.  Requests for the raw data may be submitted to Mr. Bob Castle, whose 
contact information appears at the beginning of this file.

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

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.

REFERENCES:

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.