TAO 2001 Readme File



Ship:				NOAA research vessel Ronald H. Brown

Cruise Start:			Arica, Chile, Oct 30, 2001

Cruise End:			Balboa, Panama, Dec. 3, 2001

Chief Scientist:		Michael J. McPhaden

System Operator:		Jonathan Shannahoff



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:

1.	Any values outside the range of the standards (292, 401, & 525 ppm) 

should be considered approximate (within 5 ppm).  While individual data points above 

525 may not be accurate, the general trends should be indicative of the seawater 

chemistry.

2.	On Sep. 27 at 2230, gas flow in the air phase dropped to zero because of  

clogged tubing.  For this entire cruise leg I have inserted air values from

the CO2 rug file of Pieter P. Tans and Thomas J. Conway of the NOAA Climate 

Monitoring and Diagnostics Laboratory (CMDL).  This file gives atmospheric CO2 

concentrations by latitude band through 2000.  The replaced air values were derived

by adding 1.8 ppm to the values for each latitude band after matching the time of year.  

The value of 1.8 ppm is the average increase from November 2000 to November 2001 

(personal communication from Tom Conway).



For questions or comments contact:

Bob Castle

4301 Rickenbacker Causeway

Miami, FL 33149

305-361-4418

castle@aoml.noaa.gov