Nopp 1999 Leg 3 Readme File

Ship:			NOAA research vessel Ronald H. Brown
Cruise Start:		Dutch Harbor, AK, October 5, 1999
Cruise End:		Seattle, WA, October 23, 1999
Chief Scientist:	Hugh Milburn, Marilyn Roberts
System Operator:	Marilyn Roberts

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 3:
1. The uncontaminated seawater intake was shut down 5 times due to 
rough weather.  The outages occurred on YD 285.883 (7 hrs), 
286.625 (2 1/2 hrs), 286.875 (3 1/2 hrs), 288.149 (13 hrs), and 
289.434 (9 hrs).  All water xCO2 values for these time periods 
have been removed.  In some cases when the pCO2 system was left 
on during an outage, I have retained the air xCO2 values.
2. On YD 293.660 the seawater intake was shut down for maintenance 
for 4 hours.  The underway system was also shut down during this 
period.
3. On YD 287.261 the low standard tank was changed from 298.46 to 
283.26 ppm because the tank was near empty.
4. The last 3 hours (coming in to Seattle) have very high water xCO2 
values.  Because temperature and salinity were both changing 
rapidly, I left these in the final data file.  However, a sharp 
rise in the voltage response of the low standard gas indicates 
that the Licor sample cell was not being flushed completely.  
Since the water xCO2 values are well above the high standard gas 
concentration, the numbers given in the data file are probably 
not entirely accurate.

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