Vents98 Leg 3 Readme File

Ship:			NOAA research vessel Ronald H. Brown
Cruise Start:		Newport, OR, August 24, 1998
Cruise End:		Victoria, BC, Canada, September 20 1998
Chief Scientist:	Bob Embley
System Operator:	Jim Gendron
Expocode:               33RO19980826 

Method:
Infrared absorption of dry gas.  Measurement of fugacity of Carbon 
Dioxide in surface water and air using continuous sampling methods.  
See Wanninkhof and Thoning, 1993 in Marine Chemistry, 44, 189-205 
for details of the system.  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).

Notes for Leg 3:
1. The ship's salinity sensor began giving erratic readings starting 
on day 256 and continuing to the end of the cruise.  I replaced 
these values (from year day 255.75 to the end) with salinity values 
I derived from the YSI salinity sensor attached to the system.  I 
used data from the beginning of the cruise to day 255.75 to come up 
with a linear equation relating the two.  The equation used was:  
SCS salinity = 0.907480 * YSI salinity + 2.861642 with R^2 = 
0.910347.
2. The computer crashed on day 258.642 and the system was down for 
eight hours (until 258.972).
3. On day 260.711 the low standard tank was changed from 299.06 ppm to 
283.26 ppm.
Nov. 30, 2000:
3. The feed from the ship's computer system (SCS) gave only 3 significant
digits in latitude and longitude for the first 1114 rows in the data file.
I 'fixed' this by interpolating values in both the latitude and longitude
columns.  This should be a fairly close approximation to the actual cruise
track.  If I can locate the original data from the ship, I will replace the
interpolated values with the actual ones.

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