Preliminary data Report
May 4, 1992

A.	Cruise Narrative

A.1	Highlights

A.1.a	WOCE designation:	AR4E/AR4W/AR15

A.1.b	EXPOCODE		06mt16/3

A.1.c	Chief Scientist:	Dr. Fritz Schott
				Institut Fuer Meereskunde
				Universitat Kiel
				Dusternbrooker Weg 20
				24105 Kiel Germany
				Phone:  49-431-597-3820
				Telefax: 49-431-597-3821

A.1.d	Ship name:  	R/V METEOR  
A.1.e	Ports of call: 	Belem, Brazio - Las Palmas, Canary Islands, Spain
A.1.f	Cruise Dates:   	23 May - 17 June 1991

A.2	Cruise Summary

A.2.a	Geographic Boundaries

A.2.b	Total number of stations Occupied

Total number of CTD stations: 	60

Sampling equipment:

small volume sampling:	one 24-place rosette with 10-liter bottles
CTD system:			NBIS Mark III CTD, with ƒ2 sensor and pinger
Salinometer:		2 Guildline Autosals
ADCP:				150 kHz ADCP manufactured by RDI, USA
Pegasus:			Benthos-Pegasus
Chlorofluorocarbons:	GC, Integrator: Shimadzu
Oxygen:			Winkler titration
XBT:				Sippican Deep Blue probes

Sampling: Water sampling on the cruise included measurements of salinity, both 
by CTD and water bottle samples, CTD and bottle sample oxygen determinations, 
CTD temperature. Tracer analysis were made for CFC-11 and CF-12.

A.2.c	Floats and drifters deployed
A.2.d	Moorings deployed or recovered

A.3	List of Principal Investigators

Table 1: List of Principal Investigators

Measurements:
Parameter               Sampling group  Responsible investigator
------------------------------------------------------------------
CTD O2 / Rosette        IfM Kiel        Lothar Stramma
Chlorofluorocarbons     IfM Kiel        Monika Rhein
ADCP                    IfM Kiel        Jurgen Fischer
Pegasus                 IfM Kiel        Uwe Send
Salinity                G.Britain       John Swallow
Oxygen                  IfM Kiel        Joanna Waniek
XBTs                    IfM Kiel        Lothar Stramma
------------------------------------------------------------------

IfM Kiel
Institut Fuer Meereskunde
Universitat Kiel
Dusternbrooker Weg 20
24105 Kiel 
Germany

A.4	Scientific Programme and Methods

Leg 3 of METEOR cruise 16 focused on the investigation of the circulation and  
the water mass exchange in the western tropical Atlantic. This investigation  
was carried out in the context of the World Ocean Circulation Experiment(WOCE).
The cruise was a follow-up study to the investigations done during METEOR cruise 
14/2 in October 1990. The western tropical Atlantic plays an important role in 
the water mass exchange between the northern and the southern hemisphere. The 
meridional heat transport takes place by warm surface water and subpolar 
intermediate water from the southern hemisphere moving northward in the upper 
1000 m, and North Atlantic Deep Water (NADW) moving southward between1200 and 
4000 m. The details of this water mass exchange across the equator and the 
seasonal changes of the flow field are not well understood, and were the main 
subject of this cruise.

METEOR left Belem (Brazil) on May 23, 1991 at 6:00 local time, heading towards
a location near 44ƒW, where the first hydrographic section along 44ƒW started.
On May 24 at 10:00 UTC the first CTD station was done on the Brazilian shelf at
0ƒ00.54'N, 44ƒ24.49'W (station number 286, Flg.1; CTD-cast number 1, Fig.2).  
From this location a hydrographic section with CTDs and Pegasus-drops  along 
44ƒW was done until the evening of May 27.  As a new technique an ADCP connected 
to the CTD-rosette was lowered with the  CTD. The 44ƒW section was finished at 
4ƒ43'N. From here the ship sailed to the northernmost location of the 35ƒW 
section, with XBT-drops and 4 shallow CTD/ADCP stations along the way.

The second hydrographic section with CTD/ADCP and Pegasus measurements was  
carried out along 35ƒW and started at 2ƒ30'N on May 30, 1991. This section was
completed on May 6 on the Brazilian shelf at 5ƒ38.82'S, 34ƒ57.51'W. Another  
short hydrographic section was done along 5ƒ30'S from the Brazilian shelf to  
32ƒW. Along this section the CTD was used without the ADCP because of technical
problems with the ADCP. From the endpoint of this section the ship headed NNE  
toward 30ƒW and the equator, with 7 more shallow CTD stations south of the  
equator and one Pegasus-drop on the equator, on June 10. This was the 
termination of the measurement program. Then the ship headed north towards the 
Canary Islands with XBT-drops as the only measurements between the equator and 
12ƒ30'N. The ship reached Las Palmas at 12:00 local time on June 17, where the 
cruise METEOR 16/3 terminated.

A.5	Major Problems and Goals not Achieved
A.6	Other Incidents of Note
A.7	List of Cruise Participants


B.	Underway Measurements

B.1	Navigation and bathymetry
B.2	Acoustic Doppler Current Profiler (ADCP)
B.3	Thermosalinograph 
B.4	XBT and XCTD
B.5	Meteorological observations
B.6	Atmospheric chemistry
  
                    

C.	Hydrographic Measurements

D.	Acknowledgments

E.	References

Unesco, 1983. International Oceanographic tables. Unesco Technical Papers in 
Marine Science, No. 44.

Unesco, 1991. Processing of Oceanographic Station Data, 1991. By JPOTS editorial
panel.

F.	WHPO Summary


Several data files are associated with this report.  They are the metr16l3.sum, 
metr16l3.hyd, metr16l3.csl and *.wct files.  The metr16l3.sum file contains a
summary of the location, time, type of parameters sampled, and other pertinent
information regarding each hydrographic station.  The metr16l3.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 metr16l3wct.zip. The metr16l3.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 metr16l3.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.  

G.	Data Quality Evaluation

Hydro (Affonso Mascarenhas)

The data, I was asked for to evaluate, comprise CTD and bottle data (salinity 
and oxygen) collected on two cruises from AR15/ar4.  The first one, leg 2 of 
Meteor cruise 14, was from Cape Verde Island to Salinopolis and Recife, Brazil.  
No CTD oxygen was reported for this cruise due to problems with the titration of 
dissolved oxygen and he calibration of the CTD oxygen sensors, according to an 
additional note of the cruise report.

A figure showed the histogram for the differences (Bottle-CTD) salinity, for leg 
2 Meteor cruise 14.  The standard deviation is 0.0024, that is the expected 
accuracy attained with altosal salinometers, in spite of the WOCE requirement of 
0.001.  Also 66 percent of the differences are within this range definition the 
sample as a reasonable data set since the distribution is no Gaussian.  Many
plots were performed in order to evaluate their quality and in all of then the 
distribution of the points indicate the data set as a good quality one.  As an 
example a figure showed (bottle-CTD) salinity versus station number and a 
figured showed (bottle-CTD) salinity verses salinity.  Another figured showed an 
intriguin distribution of points in the trace, that was also observed in others 
stations.  I checked the data set and replotted the TS on difference scale 
range, and it is hard to affirm if they are real or caused by shed wakes, 
pressure reversals or ship heave.

The only data flagged as questionable in this set were:

Station	sample	bottle	pressure	salinity
630		10		17		698		34.5490
632		11		16		21		36.0320

The second data set was from leg 3 of Meteor cruise 16 from Belem, Brazil to Las 
Palmas, Canary Island.  In this case we have CTD and bottle salinities and 
oxygen, being both parameters not observed in some depths as indicated in files 
*.hy2.  A figure shows the histogram from the differences (bottle-CTD) salinity, 
the distribution has a positive skewness and a standard deviation of 0.0019 that 
is the accuracy of Autosal salinometers, even though as stated before an 
accuracy of 0.001 could be attained.

On the other hand, 56 percent of the differences are within this range,
meaning that statistically there is a poor agreement between the set of 
differences with their mean.  In spite of this, both salinities fits very well 
as well as with the TS relationships of the area.

Other figures display a cluster of data between +/- 0.005 which is a guarantee 
of the goodness of the data set.  The additional information to the data report 
refers to an offset that would result by using the upcast bottle data for the 
calibrations of the meteor 14 and 16 salinity profiles.  The salinity data set 
could be considered good even with the offset caused by the used of the upcast 
bottle data.

A histogram for the differences (Bottle-CTD) Oxygen was done.  The comparison of 
the Oxygen Bottles and CTD is impressive.  The standard deviation of the 
differences is 16.39, and most of the data fell within it (80%).  In the
dissolved oxygen data set the differences shows a bias being the titration 
values less than the CTDOXY values most of the times.  The Oxygen values agree 
with the historical values of the region the systematic low values (below the 
mean for the region) between 200 and 350 m in the station 339 to 343 seems to be 
real (I probably need a better oxygen data bank for the region).  How the CTDOXY
values should be calibrated it is left to WHP Office.


Notes by T.J. Joyce

The water sample -CTD differences are expected to exceed WHP specifications as 
both quantities have error.  One expects deep values to show little difference.  
However, there is a persistent differences for pressures greater than 1500 dbar 
for groups of stations on both cruises (289-297 and 307-316 Meteor 16 and 627-
634 on Meteor 14) That suggests that the CTD data could be better 'calibrated'.
