COARE Profiling Current Meter Data 
	      PRELIMINARY DATA -- SUBJECT TO REVISION 
                          28 June 1994

	This is the general information README file for 
COARE PCM data.  There are README files for each PCM deployment
that contain information specific to that data set.  Please
contact Dr. Charles Eriksen (c.eriksen/OMNET or charlie@ocean.
washington.edu) prior to using this data.  For help accessing 
the data or questions concerning processing or reading the data, 
please contact Neil Bogue (bogue@ocean.washington.edu).

	The Profiling Current Meter is described in Eriksen,
Dahlen, and Shillingford, "An Upper Ocean Moored Current
and Density Profiler Applied to Winter Conditions Near
Bermuda", JGR, 87, 7879-7902, 1982.

	PCM profile data is vertically averaged and filtered.  
The instrument samples at 1 Hz during its profile.  These samples
are averaged on-board the instrument into five-meter-wide depth
bins, approximately centered on even five-meter-multiple depths.
The instrument typically takes about 30 seconds to traverse a
depth bin, so each bin's measurement is the average of about 
30 samples.  This averaging reduces surface wave contamination 
of current measurements.

	Special attention was paid to the temperature and
conductivity observations.  If the PCM occupied a depth
bin for less than 10 seconds, temperature and conductivity
observations in that bin were rejected.  Temperature and
conductivity observations during the two stationary one-minute
averaging periods that initiate and conclude each profile 
were rejected.  Velocity observations were retained in all cases.

	Data channels are disabled during the PCM's buoyancy
adjustment maneuvers.  This may result in gaps in a profile
if the buoyancy adjustment maneuver spans a bin.

	The discrete sampling interval and variation of 
ascent rate means that the width of the depth bins varies 
slightly from bin to bin, and the center of the bins varies
slightly from profile to profile.  A filter is applied to the
profile data to calculate values at the centers of fixed depth 
bins.  The filter gain is triangular, with gain of unity at the 
center of a given depth bin and decreasing linearly to zero 10 
meters above and 10 meters below the bin center.  This action
creates profiles of regularly spaced samples at depths that are 
the same for each profile.

	Gaps in the data have been filled in two ways.  First,
internal gaps in profiles were filled using cubic splines.
Second, one- and two-point gaps in the time-series at a given
depth were filled by linear interpolation.

	Velocities are in cm/s, v is positive northward, and 
u is positive eastward.  Temperature is in degrees Celsius,
and salinity is in practical salinity units.  

	Files are ASCII, named by station, variable, and 
the tag 'ascii'.  For example, N.t.ascii is the temperature
data at the N mooring. They are normally stored in UNIX compressed
('.Z') format, but can be made available in uncompressed format.
Formats are described in the README files for each station
(PCM_N.README and PCM_E.README).  

For further information, please contact:

Neil M. Bogue                       Office : (206) 543-4485
School of Oceanography  WB-10       FAX    : (206) 685-3354
University of Washington            email  : bogue@ocean.washington.edu
Seattle WA  98195