This disk has two primary components: the main WOCE current meter data archive, and an additional archive that contains four data reports from the OSU Buoy Group. All of the current records in the main archive have the netCDF format. Records in the four data reports have the OSU "Stranger" format. Both formats are described here.
netCDF is a relatively compact binary format. It is self-documenting: that is, each file contains metadata that describe the file - where and when the data were gathered, which parameters are present, what their units are, etc. We have employed the netCDF format here in response to an initiative in the oceanographic community to establish a common data format. It appears at present that netCDF may eventually gain wide currency. It is both compact and flexible and is an excellect medium for time series and other dimensional data.
Our implementation of netCDF is based on a standard established by the Unidata Program Center of UCAR. The netCDF standard is described on UCAR's website:
From this site you can download a user's guide and software for several different operating systems.
The data in the present archive are presented as files that contain one or more time series. Each file corresponds to one instrument. Consider, for example, an experiment in which 30 instruments produced data. The experiment will be represented here by 30 files, one for each instrument. If a particular instrument recorded, say, speed, direction, temperature, and pressure, the file from that instrument will contain 6 time series: speed, direction, eastward component, northward component, temperature, and pressure. Note that we have redundantly included the two current components as well as speed and direction.
Software to access and manipulate netCDF is widely available. Of particular interest is the Matlab/netCDF interface created by CSIRO. This add-on to Matlab is described at the UCAR website referenced above, along with many other packages. We include on this disk a short script that utilizes the Matlab/netCDF interface to read a current meter record of the type included on this disk.
This disk also contains a Fortran subroutine that you can use to read netCDF current records. If this routine is incorporated into a Fortran calling program it will pass a user-specified subset of the time series in a current record back to the program for analysis.
Another useful application is the UCAR utility NCDUMP. NCDUMP reads a netCDF file and produces ASCII output that shows metadata and one or more of the time series in the file. NCDUMP is run from the UNIX or MS-DOS command-line interface. As an example, the listing below (in green) was produced by the command
ncdump -v speed rcm01000.nc > speed.cdl
In this command rcm01000.nc is the name of the input file, a netCDF current meter record on this disk. speed.cdl is the name of the output file, and is arbitrary (you can choose any name you wish). The command requests metadata and just one time series, current speed. -v is a flag that requests a particular time series or combination of time series. In this case only speed is requested.
netcdf rcm01000 {
dimensions:
time = UNLIMITED ; // (11831 currently)
variables:
double woce_date(time) ;
woce_date:long_name = "date (yr, mo, day)" ;
woce_date:units = "YYYYMMDD" ;
woce_date:valid_range = 19500101, 20501231 ;
double woce_time_of_day(time) ;
woce_time_of_day:long_name = "time (hr, min, sec)" ;
woce_time_of_day:units = "hhmmss.dd" ;
woce_time_of_day:valid_range = 0., 235959.99 ;
float speed(time) ;
speed:units = "m/sec" ;
speed:valid_range = 0., 3. ;
float direction(time) ;
direction:long_name = "true direction (toward)" ;
direction:units = "degrees, clockwise from N" ;
direction:valid_range = 0., 360. ;
float u(time) ;
u:long_name = "eastward velocity component" ;
u:units = "m/sec" ;
u:valid_range = -3., 3. ;
float v(time) ;
v:long_name = "northward velocity component" ;
v:units = "m/sec" ;
v:valid_range = -3., 3. ;
float temperature(time) ;
temperature:long_name = "water temperature" ;
temperature:units = "degrees C" ;
temperature:valid_range = -2., 35. ;
float pressure(time) ;
pressure:units = "decibars" ;
pressure:valid_range = 0., 12000. ;
// global attributes:
:experiment_name = "BEST (ACM4)" ;
:mooring_name = "BEST 4" ;
:pi_name = "R.D.Pillsbury/A.L.Gordon" ;
:instrument_type = "Aanderaa RCM-8" ;
:latitude = "-30.0032" ;
:longitude = " 5.9958" ;
:instrument_depth = "210.0 m" ;
:seafloor_depth = " 5180 m" ;
:sampling_interval = " 60 min" ;
:earliest_start_time = "23-jun-1992 18:00:00" ;
:latest_stop_time = "29-oct-1993 16:00:00" ;
:null_value = -999.9 ;
data:
speed = 0.1661, 0.1575, 0.1719, 0.2035, 0.1834, 0.1891, 0.192, 0.192,
0.2006, 0.1546, 0.1259, 0.1345, 0.1431, 0.1316, 0.1431, 0.1259, 0.0801,
0.0801, 0.0972, 0.0915, 0.1087, 0.1374, 0.1604, 0.169, 0.1805, 0.1805,
0.192, 0.1863, 0.192, 0.2064, 0.192, 0.1978, 0.2006, 0.2006, 0.1805,
0.1805, 0.1632, 0.1345, 0.1288, 0.1001, 0.0801, 0.0773, 0.0744, 0.0659,
0.0547, 0.0773, 0.1201, 0.1661, 0.1949, 0.1863, 0.1949, 0.2035, 0.2122,
0.2064, 0.1863, 0.169, 0.1632, 0.1604, 0.1604, 0.1489, 0.123, 0.0915,
0.0575, 0.0382, 0.0355, 0.0382, 0.0491, 0.0463, 0.0575, 0.0801, 0.1173,
0.1345, 0.1604, 0.1776, 0.1978, 0.1863, 0.1431, 0.1374, 0.1316, 0.1001,
0.0716, 0.0491, 0.0463, 0.0519, 0.0858, 0.1144, 0.1345, 0.1087, 0.1144,
.
.
.
This listing shows metadata and the first 10 lines of the speed series. Note that the output series can be accessed by any application that is capable of reading comma-delimited data. The format shown above is called "CDL" by UCAR. CDL stands for Common Data form Language. NCDUMP is described in the netCDF user's guide, which you can download from UCAR.
Other netCDF routines available from UCAR for the UNIX and MS-DOS environments provide complete access to and control of the netCDF format. UCAR's package is written in the C language but contains a Fortran interface to the C routines. The Fortran program mentioned above, which is on this disk, utilizes the UCAR package. If you would like to learn more about netCDF we suggest you read the netCDF primer prepared by Nathan Bindoff.
We are aware that users who are unfamiliar with netCDF or who lack software to deal with it may find the netCDF format more a deterrant than an aid to effective use of the data. The OSU Buoy Group has for many years provided current meter data to other organizations in a simple ASCII format that we have named the Stranger format ("Stranger" because any stranger can easily understand and use it). We have included in this CDROM set a second disk identical to this one, except that all the files have the Stranger format. This format is easily readable by both humans and computers; you may find it preferable to netCDF. We show below a portion of the Stranger version of the netCDF file displayed above:
22 header lines
11831 data lines
(i4,3i3,f8.2,f7.1,2f8.2,f8.3,f8.1,i6)
Experiment name: BEST (ACM4)
Mooring name: BEST 4
Mooring position: 30.003 deg S, 5.996 deg E
Instrument depth: 210 meters
Seafloor depth: 5180 meters
Instrument type: Aanderaa RCM8
CMDB accession number: 1000
Parameters:
hour
day
month
year
speed (cm/sec)
dir (deg true)
u (cm/sec)
v (cm/sec)
temp (deg C)
pressure (db)
line count
1800 23 6 92 16.61 283.0 -16.19 3.74 14.352 232.0 1
1900 23 6 92 15.75 289.0 -14.89 5.13 14.477 231.2 2
2000 23 6 92 17.19 286.0 -16.52 4.74 14.139 231.2 3
2100 23 6 92 20.35 282.0 -19.91 4.23 14.050 230.5 4
2200 23 6 92 18.34 275.0 -18.27 1.60 14.103 230.5 5
2300 23 6 92 18.91 276.0 -18.81 1.98 13.935 230.5 6
0 24 6 92 19.20 276.0 -19.10 2.01 14.094 230.5 7
100 24 6 92 19.20 275.0 -19.13 1.67 13.855 230.5 8
200 24 6 92 20.06 272.0 -20.05 0.70 13.563 230.5 9
300 24 6 92 15.46 261.0 -15.27 -2.42 13.837 230.5 10
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This file, like the netCDF dump, begins with metadata. Following the metadata, each line represents one sampling cycle and contains hour, day, month, year, speed, direction, eastward component, northward component, temperature, pressure and a line count. Note that if you read this file with a computer program, the first line of the file tells the program where the data begins, the second line tells it how many lines of data there are, and the third line describes the format of the data.
As noted above, current records in the four OSU data reports on this disk also have the Stranger format. The data reports all describe WOCE or WOCE-related experiments (ACM4, PCM11, ICM3, and the Eastern Boundary Current experiment, which was related to PCM2).
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