1. Cruise Narrative

1.1 Highlights

Expedition Designation(EXPOCODE): 49RY9106

Chief Scientist:        Masanao Imai,
                        Japan Meteorological Agency,
                        1-3-4, Otemachi, Chiyoda-ku,
                        Tokyo 100, Japan

Ship:     R/V Ryofu Maru

Ports of Call:
          Leg 1: Tokyo, Japan to Rabaul, Papua New Guinea
          Leg 2: Rabaul, Papua New Guinea to Cebu, Republic of the
                    Philippines
          Leg 3: Cebu, Republic of the Philippines to Tokyo, Japan

Cruise Dates:
          Leg 1: June 6, 1991 to June 22, 1991
          Leg 2: June 25, 1991 to July 8, 1991
          Leg 3: July 13, 1991 to July 26, 1991

1.2 Cruise Summary

Cruise Track
          The cruise track and station locations are shown in Figure
1. Observations of PR4 were carried out as part of the R/V Ryofu
Maru cruise RY9106 Leg 1, and those of PR2 were Leg 2 and Leg 3.

Number of Stations
          A total of 35 CTD/rosette stations for PR4 and 33 stations
for PR2 was occupied using a General Oceanics 12 bottle rosette
equipped with 12 1.7-liter Niskin water sample bottles, and an NBIS
MK III B CTD. No additional sensors were used with the CTD system.

Sampling
          The following water sample measurements were made:
salinity, oxygen, nitrate, nitrite and phosphate on all stations. 
The depths sampled were: 10, 25, 50, 75, 100, 125, 150, 175, 200,
250, 300, 400, 500, 600, 700, 800, 900, 1000, 1250, 1500, 2000,
2500, 3000, 4000 in meters at every 5 degrees in latitude. On other
stations, water samples were taken at shallower depths than 1250m.
Surface water samples were collected by a bucket at every station.

1.3 List of Principal Investigators

          The principal investigators responsible for each 
parameters measured on the cruise are listed in Table 1. (All the
correspondence on these data should be addressed to the Director
of the Oceanographical Division, Marine Department, Japan
Meteorological Agency.)



          Name                  Responsibility           Affiliation

          H. Minami             CTD, S                   JMA/MD
          K. Fushimi            O2, Nutrients            JMA/MD

          JMA/MD  Marine Department, Japan Meteorological Agency

Table 1. Principal Investigators for all measurements.



2. Measurement Techniques and Calibrations

2.1 CTD

          The CTD is NBIS Mark III B. An HP9000 Series 300 model 330
(Hewlette Packard) with 4 MByte of memory was used as the primary
data collection device and all FSK signals of CTD data were backed
up using the digital audio tape (DAT). The original sampling rate
is 31.25 samples per second, however, our software gets around 20
samples per second and compress these into one tenth of collected
data.

          The temperature and pressure sensor were calibrated at the
calibration facility of HAKUTO Co., Ltd. before the cruise. The
results are shown in Table 2.


                    Temperature; linear fit

                    Time               Bias         Slope
Pre-Cruise (12 January 1991)        +0.1246      0.999874

                    Pressure(increase); linear fit

                    Time               Bias         Slope
Pre-Cruise (16 January 1991)        -0.8331      1.000787

Table 2. CTD Calibration contents at laboratory


          The conductivity sensor was calibrated at sea using data
from the measurements of salinity collected at 4 stations on PR4
and 6 stations on PR2. The salinometer is AUTOLAB model 1601 for
the measurements of salinity of the water samples. The results are
shown in Table 3. The calibration constant is determined assuming
that the bias zero.


                                          Bias               Slope

          RY7945-7979(Leg 1)               0.0             0.99990
          RY7980-7989(Leg 2)               0.0             0.99979
          RY7992-7999(Leg 3)               0.0             0.99988
          RY8000-8014(Leg 3)               0.0             0.99950


Table 3. The conductivity scaling factor

          The temperature in "-.SEA" and "-.CTD" files are described
with the international temperature scale of 1990 (ITS-90).

2.2 Oxygen Measurements

          The determination of dissolved oxygen was done by the
modified version of the Winkler method described in "Kaiyo Kansoku
Shishin (Manual on Oceanographic Observation)" published by the
Japan Meteorological Agency(1970). The reagent blank was not
subtracted. No estimation of accuracy and precision has been done.

          Because no temperature data when samples were taken from
bottles are recorded, it was assumed that the density of samples
is 1022.156 kg/m3 (which assume the temperature for 28 degree C and
salinity for 34.68) and use this value to convert from umol/l to
umol/kg.

2.3 Nutrients Analyses

          The nutrients analyses were done by the Technicon Auto
Analyzer II described in "Kaiyo Kansoku Shishin (Manual on
Oceanographic Observation)" published by the Japan Meteorological
Agency(1970). No estimation of accuracy and precision has been
done.

          Because no temperature data while analyses are recorded,
it was assumed that the density of samples is 1022.156 kg/m3 (which
assume the temperature for 28 degree C and salinity for 34.68) and
use this value to convert from umol/l to umol/kg.

2.4 Noted for the -.SUM, -.SEA and -.CTD files

2.4.1 -.SUM

          The positions of observation stations were recorded at the
beginning and end of the observation and these values were only
recorded in  minutes, we describe the averaged position as the
bottom (BO).

          Since the surface water samples were taken by a stainless
steel water bucket, "Number of bottle" includes this bucket
sampling.

2.4.2 -.SEA

          Our following parameters have the less precision than the
required, we describe the last digit of data as blank to meet the
data format: CTD temperature, CTD salinity, salinity, oxygen and
nitrates.

2.4.4 -.CTD

          CTD temperature and salinity data have the less precision
than the required, we describe the last digit of data as blank to
meet the data format.

          The number of samples averaged at the pressure level was
not available because our software was not recording the number of
data during data processing.

3. References

Japan Meteorological Agency, 1970: Kaiyo Kansoku Shishin (Manual
          on Oceanographic Observation). (in Japanese)
