1    CRUISE NARRATIVE  (PR18)

1.1  HIGHLIGHTS

                         WOCE Line  PR18
                     WOCE ExpoCode  49TU9104_1
            Expedition Designation  Chofu Maru Cruise NC9104
                   Chief Scientist  Michio Aoyama/NMO
                              Ship  R/V Chofu Maru
                     Ports of Call  None
                      Cruise Dates  April 27 to May 7, 1991


    
1.2  CRUISE SUMMARY

Observations of PR18 were carried out as a part of the R/V Chofu Maru Cruise 
NC9104 Leg1. The ship sailed from Nagasaki at 0600 UTC on 27 April 1991. By 
2300 UTC on 1 May the ship was at the first station of a section PR18. The 
cruise track and station locations are shown in Figure 1. At 1426 UTC on 2 May 
just finished the observation at PN-5, we interrupted the observation of PR18 
and took 11 hours trip to the ocean data buoy near the PR18 line. The location 
of the ocean data buoy is 28 10'N, 126 20'E and the depth at the buoy is 133 
meters depth. The purpose of this was the routine maintenance and confirmation 
of the buoy. The ship returned to the station PN-5 on section PR-18 on 3 May 
and restarted the observation. At 2335 UTC on 3 May the ship was at the last 
station of a section PR18 and the observations of PR18 ended at 0129 UTC on 4 
May. The CTD and multisampler were good throughout the cruise. 


1.3  PRINCIPAL INVESTIGATORS FOR ALL MEASUREMENTS

The principal investigators for all the parameters measured on the cruise are 
listed in Table 1.


Table 1. Principal Investigators for All Measurements

                 Name         Responsibility  Affiliation
                 -----------  --------------  -----------
                 Y. Tomiyama  CTD             NMO
                 M. Aoyama    S,O2,Nutrients  NMO


1.4  List of Cruise Participants

The cruise participants for two legs are listed in Table 2.


Table 2. Cruise Participants

                Name          Responsibility   Affiliation
                -----------   --------------   -----------
                M. Aoyama     Chief Scientist  NMO
                              S,O2,Nutrients   
                E. Moriyama   Watch Stander    NMO
                T. Hinata     Watch Stander    NMO
                Y. Takatsuki  S,CTD Hardware,  NMO    
                              CTD Software
                T. Nakano     Watch stander    NMO
                H. Kamiya     Watch Stander    NMO
                T. Shimizu    O2,Nutrients     NMO
                J. Jifuku     O2,Nutrients     NMO
                T. Ishihara   Watch stander    NMO
                H. Nakane     Maritime NMO
                              Meteorology   


2.   CTD
     (Michio Aoyama)

The Neil Brown Mark III B CTD (1600 dbar sensor without oxygen sensor) mounted 
in the 12 x 1.7 Liter General Oceanics rosette multisampler frame was used for 
all of the vertical CTD work.

In general at the CTD stations of which depth are shallower than 100 meters and 
than 4000 meters, the package was lowered to within 5 meters of the bottom and 
lowered to the depth of 95 percents of the bottom depth, respectively, because 
unable to use the acoustic pinger on DSF-6000 fathometer. 

The performance of the CTD and multisampler was good throughout the cruise.

A Hewlett Packard HP9000-320 with a 2 MByte of memory was used as a primary 
data collection device and all CTD data was backed up onto the audio tape. The 
original sampling rate is 31.25 samples per second, however, our software can 
get around 20 samples per second and compress it one sixth of the collected 
data due to the limitation of the memory. All of the CTD data of our 
observatory was loaded on the basis of the compressed data described above. 

The results of the laboratory calibration for the temperature and pressure are 
shown in Table 3, however, these were not used because the calibration methods 
for temperature and pressure are not decided. 


Table 3. CTD calibration constants at laboratory

            Temperature; linear fit
            TIME                       BIAS       SLOPE
            ------------------------   ---------  ---------
            Pre -Cruise 12 Mar. 1991   0.0022534  0.9999701
            Post-Cruise 10 Jan. 1992  -0.0061256  0.9998243
            ___________________________________________________
            
            Pressure increasing (0-1600 dbar range); linear fit
            TIME                       BIAS       SLOPE
            ------------------------   ---------  ---------
            Pre -Cruise 12 Mar. 1991  -0.0525     0.999349
            Post-Cruise 11 Nov. 1991   0.2826     0.999153
            
            
The conductivity scaling factor given in Table 4 is derived from not a linear 
fit but a ratio of CTD data to water sample data and were used for the final 
data load. The salinity determination of the water samples was with the 
Guildline AUTOSAL 8400A. Standard Seawarter batch of P112 was used to 
standardize the AUTOSAL. The precision of the salinity determination of the 
water samples was 0.0010 PSS derived from the standard deviation of the twenty 
three water samples collected from the same bottle.


Table 4. The conductivity scaling factor

                STATION NO.         BIAS      SLOPE
                ------------------  --------  -------
                PN-1 - PN-9           -       0.99990


 
3.  OXYGEN MEASUREMENTS
    (Michio Aoyama)

The determination of dissolved oxygen was done by the modified version of the 
Winkler method described in "Kaiyou kansoku shishin (Manual of Oceanographic 
Observation)" published by the Oceanographical Society of Japan (1970). The 
reagent blank was not subtracted. The precision was generally better than 1 
µmol/l at the concentration of surface level. No estimation of accuracy has 
been made.


4.  NUTRIENT ANALYSES
    (Michio Aoyama)

The nutrients analyses were done by the Technicon Auto Analyzer II described in 
"Kaiyou kansoku shishin (Manual of Oceanographic Observation)" published by the 
Oceanographical Society of Japan (1970). 

Sampling for nutrients followed that for dissolved oxygen on average 10-20 
minutes after the casts were on deck. Samples were drawn into 10 cm3 glass, 
narrow mouth, screw-capped bottles. Then they were immediately introduced on 
the sampler tray of the Technicon Auto Analyzer II for the analysis and 
generally the analyses were begun within one hour after the casts were on deck. 
if the delays were anticipated to be more than one hour, the samples were 
refrigerated. Samples were refrigerated and stored up to one hour on stations 
PN-8, PN-6, PN-4', PN-4, PN-3', PN-3, PN-2 and PN-1. 

The precisions of the onboard Nitrate and Nitrite analyses estimated from the 
standard deviation of the five samples from the same working standard solution 
on each analysis are shown in Table 5. The precision of the onboard Phosphate 
analysis estimated from the standard deviation of the four samples from the 
same working standard solutions are also shown in Table 5. The concentrations 
of the working standard of nitrate, nitrite and phosphate were 40 µmol/l, 2 
µmol/l and 3 µmol/l, respectively. No estimation of accuracy have been made.


Table 5. The median and the range (in the parentheses) of the precision of the 
         onboard nutrients analyses.
         unit:%

                 Nitrate        Nitrite         Phosphate
                 -------------  --------------  ---------
                 0.99           1.25            1.36
                   (0.51-2.08)    (0.05-6.22)    (0.41-4.96)       
    

The concentrations in µmol/kg of oxygen, nitrate, nitrite and phosphate were 
converted from the concentrations in µmol/l using the density calculated from 
the room temperature and salinity of the water samples. The laboratory 
temperature for each station are given in Table 6.


Table 6. Laboratory temperature for each station.

           Station  Temp.     Station  Temp.     Station  Temp.
           -------  ----      -------  ----      -------  ----
           PN-9     23.       PN-8     23.       PN-7     23.
           PN-6     23.       PN-5     23.       PN-4'    26.
           PN-4     26.       PN-3'    28.       PN-3     29.
           PN-2     29.       PN-1     28.                   



5.  NOTES FOR THE --.SUM,--.SEA and --.CTD FILES
    (Michio Aoyama)

The first 2 characters of the file name of --.SUM, --.SEA and --.CTD files are 
NC for R/V Chofu Maru of Nagasaki Marine Observatory. These characters are 
followed by the last two digits of year, the month and character R (R for PR18) 
or character S (S for PR19) for the --.SUM and --.SEA files. In addition, the 
leg of the cruise is appended in the file name of --.SEA files. For the -- .CTD 
files The characters NC are followed by the unique station number and the cast 
number given in the Comments.

The file names of the --.SUM and --.SEA for this cruise are as follows;

                              NC9104R.SUM,
                                 NC9104R1.SEA 

5.1  .SUM

Since some of the time at the bottom (BO) and completion (EN) of the cast, the 
positions at the beginning (BE), bottom (BO) and the completion (EN) of the 
cast and the water depth of station were not recorded, we leave the column of 
them blank. 

Since the surface water samplings were by a stainless steel water bucket, 
"Number of bottles" includes this bucket sampling.  The unique station numbers 
given by the Japan Meteorological Agency with the cast numbers, which are used 
as the --.CTD files name, are given in the "Comments".

5.2  .SEA

We leave "the sample number (SAMPNO)" blank because the sample numbers are 
different among the salinity, oxygen and nutrients on our assignments. 

Since the surface water samplings were by a stainless steel water bucket, we 
leave the column of "The Bottle Number (BTLNBR)" at the surface layer blank. 

All water sample quality flags for the oxygen during this cruise were "3" 
because the precision did not exceed the WOCE standard of 0.1% and no 
estimation of accuracy has been made.

5.3  .CTD

The number of samples averaged at the pressure level, NUMBER, was the estimated 
value because original CTD data were lost in the processing described in 
"Section 2. CTD".



7.  REFERENCES

Oceanographical Society of Japan, 1970. Kaiyou kansoku shishin (Manual of 
    Oceanographic Observation). Ed. by the Japan Meteoro- logical Agency. (in 
    Japanese)



8  WHPO SUMMARY

Several data files are associated with this report. They are the 91041.sum, 
91041.hyd, 91041.csl and *.wct files. The 91041.sum file contains a summary of 
the location, time, type of parameters sampled, and other pertient information 
regarding each hydrographic station. The 91041.hyd file contains the bottle 
data. The *.wct files are the ctd data for each station. The *.wct files are 
zipped into one file called 91041.wct.zip. The 91041.csl file is a listing of 
ctd and calculated values at standard levels.

The following is a description of how the standard levels and calculated values 
were derived for the 91041.csl file:

Salinity, Temperature and Pressure: These three values were smoothed from the 
individual CTD files over the N uniformly increasing pressure levels. using the 
following binomial filter-

           t(j) = 0.25ti(j-1) + 0.5ti(j) + 0.25ti(j+1) j=2....N-1

When a pressure level is represented in the *.csl file that is not contained 
within the ctd values, the value was linearly interpolated to the desired level 
after applying the binomial filtering.  

Sigma-theta(SIG-TH:KG/M3), Sigma-2 (SIG-2: KG/M3), and Sigma-4(SIG-4: KG/M3): 
These values are calculated using the practical salinity scale (PSS-78) and the 
international equation of state for seawater (EOS-80) as described in the 
Unesco publication 44 at reference pressures of the surface for SIG-TH; 2000 
dbars for Sigma-2; and 4000 dbars for Sigma-4.

Gradient Potential Temperature (GRD-PT: C/DB 10-3) is calculated as the least 
squares slope between two levels, where the standard level is the center of the 
interval. The interval being the smallest of the two differences between the 
standard level and the two closest values. The slope is first determined using 
CTD temperature and then the adiabatic lapse rate is subtracted to obtain the 
gradient potential temperature. Equations and Fortran routines are described in 
Unesco publication 44.

Gradient Salinity (GRD-S: 1/DB 10-3) is calculated as the least squares slope 
between two levels, where the standard level is the center of the standard 
level and the two closes values. Equations and Fortran routines are described 
in Unesco publication 44.

Potential Vorticity (POT-V: 1/ms 10-11) is calculated as the vertical component 
ignoring contributions due to relative vorticity, i.e. pv=fN2/g, where f is the 
coriolius parameter, N is the bouyancy frequency (data expressed as 
radius/sec), and g is the local acceleration of gravity. 

Bouyancy Frequency (B-V: cph) is calculated using the adiabatic leveling 
method, Fofonoff (1985) and Millard, Owens and Fofonoff (1990). Equations and 
Fortran routines are described in Unesco publication 44.

Potential Energy (PE: J/M2: 10-5) and Dynamic Height (DYN-HT: M) are calculated 
by integrating from 0 to the level of interest. Equations and Fortran routines 
are described in Unesco publication, Processing of Oceanographic station data.

Neutral Density (GAMMA-N: KG/M3) is calculated with the program GAMMA-N 
(Jackett and McDougall) version 1.3 Nov. 94. 
