RB-04-03
Windward Passage 2004 Cruise Readme File

Ship:			NOAA research vessel Ronald H. Brown
Cruise Start:		San Juan, Puerto Rico, March 29, 2004
Cruise End:		Charleston, SC, April 13, 2004
Chief Scientist:	Ryan Smith
System Operator:	Jonathan Shannahoff
Expocode:               33RO20040329

Method:
Infrared absorption of dried gas.  For details of the system see: 
Measurement of fugacity of Carbon Dioxide in surface water and air using continuous 
sampling methods.  Wanninkhof and Thoning, 1993 in Marine Chemistry 44, 189-205, 
And:
Feely, R.A., R. Wanninkhof, H.B. Milburn, C.E. Cosca, M. Stapp, and P.P. Murphy, 
A new automated underway system for making high precision pCO2 measurements 
onboard research ships, Analytica Chim. Acta, 377, 185-191, 1998.

The three standard gases come from CMDL in Boulder and are directly traceable to 
the WMO scale.

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.

Notes:
1.	Any values outside the range of the standards (296.73, 357.18, & 423.28 ppm) 
should be considered approximate (within 5 ppm).  While individual data points above 
423 or below 296 may not be accurate, the general trends should be indicative of the 
seawater chemistry.
2.	At the beginning of the 2004 field season, two mistakes were made in setting up
the system.  The first error was in the plumbing of the equilibrator and may result
in slight inaccuracies in the water xCO2 values and some additional variance in the
values.  The increased variance should be less than 2 ppm and probably less than 1 
ppm.  The second error was in plumbing the water flow meter backwards and resulted 
in flow values of approximately 3.5 liters per minute in the data file.  I believe 
that the true flow was in the normal range of approximately 11 liters per minute.  
This problem should have no effect on xCO2 values.  Both of these problems were 
corrected after the fourth cruise (RB0404).
3.	The last 19 hours of data (from April 12 @ 1845 to April 13 @ 1325) was removed
due to insufficient flow of gases in all phases.  Licor voltages were also bad.
4.	A group from the University of South Florida led by Zhaohui Aleck Wang teed off
of our standard gases and air line feed during this cruise to test a new pCO2 
instrument they are developing.  We believe this had no deleterious effect on the
data collected.


For questions or comments contact:
Bob Castle
4301 Rickenbacker Causeway
Miami, FL 33149
305-361-4418
robert.castle@noaa.gov