Gasex98 Leg 1 Readme File

Ship:			NOAA research vessel Ronald H. Brown
Cruise Start:		Miami, FL, May 7, 1998
Cruise End:		Lisbon, Portugal, May 19, 1998
Chief Scientist:	Jim Butler
System Operator:	Bob Castle
Expocode:               33RO19980507

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. 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.
2. The system was down on May 16 for 1-1/2 hours to recalibrate the YSI 
TSG.
3. 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.
4. 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.
5. 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

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