Dear Mark,

Thank you for your DQE evaluation of CTD data collected along WOCE sections
P14S and P15S.  We considered each of your suggestions and the following is
an itemized explanation of what we did or didn't change in our data files,
as well as answers to your questions.

Kristy McTaggart and Greg Johnson

***************************************************************************


STATION SUMMARY FILE (.sum)

Stations 21 and 77 should be listed as cast 1.  The .sum and .ctd files
should be corrected.  We've corrected our files here.

The uncorrected sounder depth at the bottom of the cast for stations 44 and
55 may appear erroneous.  However, these are not typos.  They are the
values calculated from the ship's PDR during acquisition.  The bottom at
station 44 in particular was noted to be strongly sloping.  We did not
change these values in our files.

The PDR sound speed used for sounder readings was 1500 m/s.  The readings
were not corrected for transducer depth below the waterline.  The depth of
the transducer would've been about 5.5 +/- 0.6 m.  We would prefer to use
the PDR depths as listed and correct them using Carter's tables so that 
they serve as independent measurements and can be used as a check on CTD
pressure.


SALINITY 

'Scatter of salinity residuals'

There is an incompatibility between the General Oceanics rosette sampler
and the Sea-Bird 911plus CTD system that generates a spike in the data
stream at the moment a bottle is confirmed as tripped.  Because of this,
upcast CTD burst data had to be averaged prior to the bottle confirm bit.
Two-second averages were chosen over a longer interval because the CTD
operators did not always let the package sit at bottle depth for at least
10 seconds before firing the rosette.  Hence no changes were made.


'Biasing of CTD salinity data for individual stations'

Of course one can seemingly make a (very slight) improvement in the 
CTD-bottle residual statistics by allowing more degrees of freedom in the
fit as the DQE has suggested (that is, breaking up the fit into small 
station groupings).  One could get the best statistics by individually
fitting each station to its bottles, but most experts would argue that
this would be a bad choice, because one would not be taking advantage of
the CTD calibration as a way to average out station-to-station bottle
salinity noise.

We believe that the SBE-9/11 CTD conductivity slope drifts gradually, and
is actually more stable than the day-to-day fluctuations in the autosal-
inometer salinities owing to small temperature drifts in the laboratory
and the fact that severe budgetary constraints on these cruises forced us
to economize even on such things as standard sea water.  We suspect that
the "biasing of the CTD salinity data" mentioned in the DQE evaluations is
actually noise in the bottle data.  Somewhat suspicious is that the station
groupings recommended by the DQE of the correct size (most often 3-5 
stations per group) that they could easily be owing to daily drift problems
in the autosalinometer.  For our original calibrations we deliberately
chose to model the conductivity slope adjustments of the entire data sets
for P14S/P15S and P18 using 4th-order polynomial functions of station
number to average out bottle salinity noise.  We did this because we saw
no obvious jumps in the CTD calibration for either cruise, just gradual
drifts.

Statistical support for our philosophy over that of the DQE is given by
the following exercise:  The 2oC potential isotherm is well within the
oldest Pacific Deep Water, and has some of the tightest Theta-S relation-
ships in the Pacific Ocean (and probably the world).  For both P18 and
P14S/P15S, we looked at the absolute values of station-to-station changes
in CTD salinity on Theta=2.0oC (Figure 1) for our original calibration,
creating a histogram of station-to-station differences for each cruise in
0.001 bins.  We then applied the DQE's suggested ad-hoc calibrations for 
smaller station groupings to the data and conducted the same analysis.
When the histograms are differenced (Figure 2), one can see that the
Theta-S relations at 2oC after the DQE's corrections are noisier for both
cruises.  For P18, after the DQE's suggested correction there are four less
station pairs in the 0.000 difference bin and one less in the 0.001 
difference bin whereas there are three more in the 0.002 difference bin
and two more in the 0.003 difference bin.  For P15S/P15S there are four
less stations in the 0.000 difference bin after the DQE's suggested
correction, with one more in the 0.001 difference bin and three more in 
the 0.002 difference bin.  Since the DQE's "corrections" actually
introduce more noise in the CTD Theta-S relation at 2oC than our original
calibration, we decline application of them.  The small groups do not 
improve the calibraiton, they degrade, perhaps by introducing autosalinometer
drift noise.


Regarding suspicious CTD salinity data listed in Table 3, no changes were
made to any profile data (see above) nor flags associated with "transient/
despiking errors".  As for CTDSAL values in the .sea file for station 127,
we agree that they should be flagged as 3 for samples 202 to 214.  Also,
BOTSAL flags for samples 209, 210, 213, and 214 should then be changed to 2.


'Problem salinity bottle data'

Excluding stations 19, 49, 117, and 164 bottle salinity values from the
calibration of this data set as a whole would not significantly change the
fit as we have done it, thus we didn't make this adjustment.


OXYGEN

Quality flags should be ammended as suggested in Table 4.  However, stations
8, 10, and 135 will not be recalibrated individually as they are among the
first casts with a new sensor module.  As a rule, the first few casts with a
new module are problematic, and this cruise was no exception.


TEMPERATURE

The very spikey temperature structure between 100 and 300 dbar at station 
43 is also seen in salinity and has been identified as Antarctic
Intermediate Water interleaving at the front.  It is also seen at 
adjacent stations 42 and 44.  Nothing should be done to this profile.

Temperature spikes listed were examined but not changed.  Neither were
their flags changed.


DESPIKING AND INTERPOLATION

Interpolated temperature and salinity data are the result of processing
programs and not instrument or electronic problems.  In program DESPIKE
salinity profiles are viewed and interactively despiked using linear
interpolation.  Conductivity, theta, and sigma-theta are recomputed for
the interpolated records.  Only the salinity quality flag is ammended to
6.  In program DELOOP Brunt-Vaisala Frequency squared (N^2) is computed
at the mid depths and bracketed between two vectors, one padded with 
zeros at the surface and one padded with zeros at depth.  If the first
and second points of a -N^2 fail the criteria (<=-1e-05), then temperature
and conductivity are linearly interpolated and salinity, theta, and sigma-
theta are recomputed.  The quantity of interpolated points is large 
because we were working with a large package off the stern of the ship,
often in the Southern Ocean.  Hence, there was a lot of wake problems.

As for the filled surface records flagged as 7, we maintain that this is
more useful than leaving flagged bad or questionable data or removing the
data entirely.  It should be noted in the documentation that all data in 
the top 15 dbar with a flag of 7 should be regarded as questionable.


DENSITY INVERSIONS

Density inversions listed in Table 5 were examined and salinity quality
flags were changed to '3' for the following records.

Station		Pressure		Station		Pressure
    8		  5- 7			  108		   4
   10		  1- 7			  109		   1
   20		  1- 3			  110		   1
   22		  1- 5			  111		   1
   45		  1- 8			  112		   1
   49		  1- 7			  113		  1- 3
   54		   7			  117		  1- 6
   57		   1			  120		   1
   60		  5- 6			  121		   1
   64		  7- 8			  124		  1- 3
   68              1			  125		  1- 3
   69             1-14			  126		  1-13
   70		  3, 5			  131		3,5,6,10
   71		   6			  132		  1- 9
   78		  1- 9			  134		  1-3,6
   82		  1- 4			  135		   1
   83		   7			  136		   1
   84		  1- 2			  139		   8
   85              4			  140		  4, 5
   86		   1			  143		  1- 3
   87		   1			  144		   1
   88		  3, 4			  146		  1- 6
   89		  3, 4			  148		  1- 3
   90		  4, 8			  152		  1- 2
   91		  1- 4			  153		  1- 2
   99		  1- 2			  154		  1- 3
  101		  1,3,7			  155		  1-15
  102		   6			  157		  1- 4
  105		  1- 3			  159		  1- 6
  106		1-3,6,7			  160		  1-12
  107	      1-2,8,11-13		  162		  1-13
					  165		  1- 3
					  167		  1- 3
					  169		  1- 7
					  170		  1- 3
					  174		  1- 3
					  176		  1- 4
					  177		  1- 3
					  180		  1- 3
					  181		   1
					  182		  1- 2 


DOCUMENTATION

Again, the PDR sound speed was 1500 m/s, and the readings have not been
corrected for transducer depth (5.5 +/- 0.6 m) below the waterline.

The criteria used for despiking is explained above under DESPIKING AND
INTERPOLATION.