Density (Sigma-Theta):

Conductivity and temperature are first used to compute salinity, 
which is then combined with potential temperature to compute the 
potential density anomaly (sigma-theta) defined as

  sigma-theta = 1/V(S,Theta,P) - 1000 kg m**3

where V is specific volume, S is salinity, Theta is potential 
temperature, and P is set to zero.

The algorithm used is from "Algorithms  for computation of 
fundamental properties of seawater" by Fofonoff and Millard 
(UNESCO technical papers in marine science, 44, 1983).

For detailed information about sampling and sensors, 
see these two related web pages:

  http://www.pmel.noaa.gov/tao/proj_over/sensors.shtml

  http://www.pmel.noaa.gov/tao/proj_over/sampling.html

In ascii format files, to the right of the data you will 
find quality codes and sensor codes. All of these codes 
are defined below.

Using the quality codes you can tune your analysis to 
trade-off between quality and temporal/spatial coverage.

Quality Code Definitions:

0 = datum missing

1 = highest quality; Pre/post-deployment calibrations agree to within
sensor specifications.  In most cases only pre-deployment calibrations have
been applied

2 = default quality; Pre-deployment calibrations applied.  Default
value for sensors presently deployed and for sensors which were either not
recovered or not calibratable when recovered.

3 = adjusted data; Pre/post calibrations differ, or original data do
not agree with other data sources (e.g., other in situ data or climatology),
or original data are noisy.  Data have been adjusted in an attempt to
reduce the error.

4 = lower quality; Pre/post calibrations differ, or data do not agree
with other data sources (e.g., other in situ data or climatology), or data
are noisy.  Data could not be confidently adjusted to correct for error.

5 = sensor or tube failed

C (ascii) or -9 (netcdf) = Indicates special adjustments were 
made to the data. For further information, see the following:

 	Freitag, H.P., M.E. McCarty, C. Nosse, R. Lukas, M.J. McPhaden,
 	and M.F. Cronin, 1999: COARE Seacat data: Calibrations and
 	quality control procedures. NOAA Tech. Memo. ERL PMEL-115,
 	89 pp.

PDF versions of this and other PMEL Technical Memoranda and Reports 
are available on line at

	http://www.pmel.noaa.gov/pubs/PDF/pmel-pdf.html

Source code definitions:

    0 - No Sensor, No Data 
    1 - Real Time (Telemetered Mode)
    2 - Derived from Real Time
    3 - Temporally Interpolated from Real Time
    4 - Source Code Inactive at Present
    5 - Recovered from Instrument RAM (Delayed Mode)
    6 - Derived from RAM
    7 - Temporally Interpolated from RAM

Instrument code definitions:

    0 - No Sensor
    4 - Conductivity (FSI)
   14 - NextGen Conductivity
   24 - NextGen Conductivity (Firmware version 5.03+)
   70 - Seacat Conductivity
   71 - Microcat Conductivity   
   99 - Unknown