Nopp 1999 Leg 2 Readme File

Ship:			NOAA research vessel Ronald H. Brown
Cruise Start:		Honolulu, HI, September 26, 1999
Cruise End:		Dutch Harbor, AK, October 3, 1999
Chief Scientist:	Hugh Milburn
System Operator:	Marilyn Roberts
Expocode:               33RO19990926 

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 for Leg 2:
1. The system was shut down for 2 hours beginning on YD 275.143 in 
order to remount the mercury thermometer in the equilibrator.  
When the system came back up, a drop of 40 ppm in water xCO2 
values was observed.  I believe this drop was real because 
voltage response of the Licor in the water phase also dropped, 
salinity dropped about 0.15, and the fluorometer reading also 
rose 0.7 FSU.  I can find no indication of leaks prior to the 
thermometer remount that would have caused elevated xCO2 readings 
in the water phase.
2. The low standard tank was changed on YD 275.919 from 337.78 to 
298.46 ppm.

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