Tao98 Leg 1 Readme File

Ship:			NOAA research vessel Ronald H. Brown
Cruise Start:		Seattle, WA, October 13, 1998
Cruise End:		Panama Canal, November 15, 1998
Chief Scientist:	John Shanley
System Operator:	Esa Peltola
Expocode:               33RO19981015 

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 1:
1. Due to high surface water concentrations of CO2 the standard gases 
were changed during the cruise.  About a week later they were changed 
back to the original tanks.  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.  The dates and times of the tank changes were:

	#	Date	Time	YearDay	Lo Std	Mid Std	Hi Std
	Start	10/15/98 @ 1700	288.711	283.26	360.62	408.35
	Chg1	11/01/98 @ 1700	305.711	360.62	408.35	523.44
	Chg2	11/08/98 @ 2000	312.836	283.26	360.62	408.35

2. The Licor IR analyzer died 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.

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