RB-08-01 Clivar Leg 2 2008 Readme File Ship: NOAA research vessel Ronald H. Brown Cruise Start: Easter Island, Jan. 22, 2008 Cruise End: Punta Arenas, Chile, Feb. 22, 2008 Chief Scientist: Greg Johnson System Operator: Jonathan Shannahoff Expocode: 33RO20080121 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 (289.06, 370.90, & 514.29 ppm) should be considered approximate (within 5 ppm). While individual data points above 514 or below 289 may not be accurate, the general trends should be indicative of the seawater chemistry. 2. Readings of temperature and salinity from the Seabird Micro TSG in the Hydro Lab sink were bad from Feb. 8 at 1628 through Feb. 9 at 1711. Temperature readings were corrected by using the formula Micro TSG T = SST + 0.48 based on the observed temperature difference of the good data. Similarly, bad salinity readings were replaced with computed values using the difference between the ship's salinity readings and the Micro TSG when both were functioning correctly. The equation used was Micro TSG salinity = Ship TSG salinity + 0.01975. Bad values were probably caused by an interruption in the water flow through the Micro TSG. 3. The ship's salinity sensor became fouled on Feb. 11 and did not fully recover. All salinity values were replaced with salinity data from the Micro TSG in the Hydro Lab sink. In past cruises, this TSG has been seen to give more accurate salinity readings than the ship's sensor when compared to CTD trace readings. 4. Feb. 13 at 0311 through 1259, the Micro TSG temperatures were bad, probably due to intermittent water flow through the TSG. They were replaced with temperatures derived from the ship's TSG using the equation Micro TSG T = SST * 0.9892 + 0.4905. 5. The equilibrator thermistor circuitry failed during this cruise and temperatures "bottomed out" at 6.144 degrees C. Temperatures above this value seem to be accurate when compared with the temperature readings from the Micro TSG and the ship's TSG. Equilibrator temperatures from Feb. 8 at 0310 through Feb. 19 at 1932 were replaced with temperatures derived from the Micro TSG using the equation EqT = Micro TSG T * 0.995 + 0.1467. This equation is based on the relationship between the Micro TSG and the equilibrator thermistor during the rest of the cruise. 6. January 2017 made minor format changes to the header, added expocode and changed missing value to -999. Data was not altered. For questions or comments contact: Bob Castle 4301 Rickenbacker Causeway Miami, FL 33149 305-361-4418 robert.castle@noaa.gov