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Data formats

The data in this archive are available in two formats: ASCII and netCDF.

The ASCII files have a locally-developed format that we have named "stranger format". The name alludes to its use as a means of sending current meter data off-campus to "stranger" facilities. We have employed it successfully as a medium of data dissemination for many years. This format is self-documenting and will be described in detail below. We selected an ASCII format for the present archive primarily because the ASCII code is universally understood. Our goal is to provide a dataset that can be accessed by anyone, and that is likely remain accessible as software and standards change. For this reason we also have not compressed the files. As compression schemes come and go, the simple uncompressed ASCII files are likely to remain readable.

netCDF is a relatively compact binary format. Like the Buoy Group's stranger 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 included netCDF files here in response to an initiative in the oceanographic community to establish a common data format. It appears at present (mid-1999) 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:

http://www.unidata.ucar.edu/packages/netcdf/

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 60 files - 30 netCDF files and 30 stranger format files. If a particular instrument recorded, say, speed, direction, temperature, and pressure, each of the two files 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.

We show below an example of the initial portion of a stranger file. This portion contains metadata and the first 10 lines of data:


    23 header lines
  5500 data lines
(i4,3i3,f8.2,f7.1,2f8.2,f8.3,f8.1,f8.3,i6)                              
Experiment name:  Slope Undercurrent Study
Mooring name:     Skunk IV                
Mooring position:  45.352 deg N, 125.650 deg W
Instrument depth:    456 meters
Seafloor depth:     2562 meters
Instrument type:    Aanderaa RCM4/5
CMDB accession number:   7379
Parameters:  
      hour 
      day  
      month
      year 
      speed (cm/sec)    
      dir (deg true)    
      u (cm/sec)        
      v (cm/sec)        
      temp (deg C)      
      pressure (db)     
      cond (mmho/cm)    
      line count
 508 23  5 78   12.15  337.2   -4.70   11.20   4.980   470.4  32.929     1
 538 23  5 78   10.83  336.0   -4.40    9.90   5.020   470.4  32.970     2
 608 23  5 78   12.07  338.1   -4.50   11.20   4.960   470.4  32.950     3
 638 23  5 78   13.26  336.9   -5.20   12.20   4.980   470.4  32.990     4
 708 23  5 78   14.23  342.8   -4.20   13.60   5.050   470.4  33.031     5
 738 23  5 78   15.29  344.1   -4.20   14.70   4.960   470.4  32.909     6
 808 23  5 78   15.06  343.0   -4.40   14.40   5.020   469.7  32.990     7
 838 23  5 78   14.83  341.9   -4.60   14.10   5.020   469.7  32.990     8
 908 23  5 78   12.53  355.9   -0.90   12.50   4.890   468.9  32.868     9
 938 23  5 78   10.64  355.1   -0.90   10.60   5.000   468.2  33.010    10
                  .
                  .
                  .

This format is easily readable by both humans and computers. The first line tells a computer where to find the first line of data. The second line tells it how many lines of data to read, and the third line tells it how to read them. The list of parameters tells the machine (and a human) where to find particular variables. This particular file has a 30-minute time increment. It begins at 0508 hrs, 23 May 1978.

A representation of the netCDF version of the same file is shown below. To produce this representation we employed UCAR's ncdump application. ncdump is a computer program that reads a netCDF file and produces a listing in what UCAR calls the "CDL" format. The listing below is in CDL format and is an accurate representation of the netCDF file's header and the first portion of the first time series, which in this case is current speed.


netcdf rcm07379 {
dimensions:
	time = UNLIMITED ; // (5500 currently)
variables:
	float speed(time) ;
		speed:minimum_value = 0. ;
		speed:units = "cm/sec" ;
	float dir(time) ;
		dir:long_name = "true direction (toward)" ;
		dir:valid_range = 0., 360. ;
		dir:units = "degrees" ;
	float u(time) ;
		u:long_name = "eastward component" ;
		u:units = "cm/sec" ;
	float v(time) ;
		v:long_name = "northward component" ;
		v:units = "cm/sec" ;
	float temperature(time) ;
		temperature:units = "degrees C" ;
	float pressure(time) ;
		pressure:units = "decibars" ;
	float conductivity(time) ;
		conductivity:units = "millimho/cm" ;

// global attributes:
		:experiment_name = "Slope Undercurrent Study" ;
		:mooring_name = "Skunk IV" ;
		:pi_name = "R.L.Smith" ;
		:instrument_type = "Aanderaa RCM4/5" ;
		:latitude = " 45.3517" ;
		:longitude = "-125.6500" ;
		:instrument_depth = "456.0 m" ;
		:seafloor_depth = " 2562 m" ;
		:sampling_interval = "  30 min" ;
		:earliest_start_time = "23-may-1978 05:08:00" ;
		:latest_stop_time = "14-sep-1978 18:38:00" ;
		:null_value = -999.9 ;

data:

 speed = 12.15, 10.83, 12.07, 13.26, 14.23, 15.29, 15.06, 14.83, 12.53, 
    10.64, 8.72, 6.73, 4.06, 0.64, 0.61, 1.89, 3.02, 5.51, 7.02, 8.38, 9.04, 
    5.08, 4.64, 4.44, 4.81, 5.14, 8.45, 12.03, 13.38, 14.65, 15.95, 17.14, 
    15.74, 14.33, 13.71, 11.99, 10.17, 9.73, 7.03, 5.15, 3.26, 4, 1.56, 1.35, 
    2.92, 2.11, 0.64, 0.67, 1.39, 1.36, 2.69, 3.89, 6.72, 7.72, 8.38, 9.03, 
    8.5, 10.03, 10.51, 10.96, 10.68, 9.62, 8.59, 5.44, 2.1, 0.63, 0.67, 0.7, 
    0.67, 1.4, 0.63, 0.61, 0.61, 0.67, 0.67, 0.61, 3.61, 6.11, 6.62, 7.44, 
    8.15, 9.32, 8.56, 8.05, 7.62, 4.25, 4.47, 4.25, 4.3, 3.56, 0.71, 0.64, 
    1.58, 1.35, 1.3, 2.47, 3.44, 5.12, 6.91, 8.66, 7.82, 8.67, 12.36, 15.97, 
    16.76, 17.54, 15.28, 13.12, 10.31, 7.71, 3.29, 2.82, 1.73, 0.61, 0.7, ...

Following current speed, the file contains direction, eastward component, northward component, temperature, pressure, and conductivity. ncdump, the computer program that produced the listing above, can be used to extract the whole file or a portion of it. Other netCDF routines available from UCAR for the UNIX and MS-DOS environments provide complete access to and control of the netCDF format.

Note that this implementation of the netCDF format does not expicitly include the time variable (as a series). In order to save space we have included just the start time, stop time, and time increment. To construct the time of, say, the Nth speed value you would take the "earliest start time" given in the global atributes, and add to it N - 1 times the time increment.

To make it possible to include all the Buoy Group data on a single disk, all the stranger format files have been zipped. You can expand them with software utilites that are readily available in virtually every computer environment. The netCDF files, which are somewhat more compact than the stranger files, have not been compressed.

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Layout of the archive

The data on this disk are organized on three levels. The files are grouped first by ocean basin; then by experiment; and finally by data format. This structure is shown schematically below, where the folder that contains Atlantic Ocean data has been expanded to show three experiments.

The layout shown above reproduces the disk's directory structure. Each ocean has its own folder (or directory) that contains all the data from that ocean. Within each ocean folder are a number of subfolders, each of which contains data from one experiment. Finally, every experiment folder has two sub-subfolders, one for each of the two data formats. Thus the disk contains four top folders that correspond to the four oceans represented in the archive. Within those four top folders are 41 subfolders corresponding to the 41 experiments in which the Buoy Group has participated. And finally, in the experiment folders are 82 sub-subfolders (two for each experiment) that contain the data files.

A fifth top folder (shown in the diagram above, just below the Southern Ocean folder) contains several electronic data reports. The data reports originally were published on the World Wide Web. The directory that contains them is just a copy of that website. Each data report contains a desription of the experiment, a map that shows the array, various metadata, spectra, and plots of the time series.

Every experiment folder also contains a summary document that lists its contents. This document shows the latitude and longitude of each mooring in the experiment, the depth of each instrument, when it was installed, when the data ends, and which parameters were recorded. You can access these summaries from this browser, by clicking on links in another part of the archive. Every experiment summary is present in two forms: a simple text file and a web document. The web document (which is written in HTML code) is what you will see when you click on its link with a browser. The text files are included for those who are not using a web browser.

An example of a summary document, text version, is shown here:


===========================================================
 Current meter records from the Fall Transition Experiment
===========================================================

 The accession numbers shown below refer to the OSU Buoy Group's online database,
 where each file is identified by a number.  In the database and also on this disk,
 each file has a name that encodes its accession number.  Thus the ASCII (stranger
 format) version of the file whose accession number is 1234 can be found on this
 disk as rcm01234.str, and the netCDF version is stored here as rcm01234.cdf.

 The data were recorded with Aanderaa RCM5 current meters.

 See: Brad Reid et al, Current and CTD Observations off Oregon: August to
 December 1980.  OSU Data Report 116, Reference 85-7, April 1985.

--------------------------------------------------------------------------------
accession   lat     lon   depth  mooring name          dates          parameters
--------------------------------------------------------------------------------

  7236    44.994 -124.182   31      Turtle     20 Aug 80 - 01 Dec 80   s,d,t,p,c       
  7237    44.994 -124.182   56      Turtle     20 Aug 80 - 01 Dec 80   s,d,t,p,c       
  7238    44.994 -124.182   81      Turtle     20 Aug 80 - 01 Dec 80   s,d,t,p,c       
  7239    44.994 -124.182   91      Turtle     20 Aug 80 - 01 Dec 80   s,d,t,p,c
 

This particular experiment, OSU's Fall Transition experiment, produced just four current meter records from one mooring. The parameter codes in this example and in all of the summary documents have the following meanings:

s = current speed
d = current direction
t = temperature
p = pressure
c = conductivity

Note that in these tables we list just speed and direction, although whenever speed and direction both are present in a file, the file will also include the two vector components (u and v). The term "depth" refers to instrument depth in the case of a mechanical current meter and bin depth if it an ADCP.

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How to download data files

There are two ways to move data files from this disk to your computer: you can do it either by clicking on links in this browser interface, or by using the native capabilities (i.e., the operating system) of your computer.

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Browser interface

The archive's browser interface was designed for an environment with a screen resolution of at least 800 x 600 pixels and 24-bit color.

The HTML code on this disk has been tested with several standards-compliant browsers. It produces satisfactory results with Mozilla SeaMonkey, Mozilla Firefox, the Opera browsers, and several older Mozilla and Netscape browsers. You can also use the Microsoft browser, though it is not standards-compliant and of course you risk virus infection with any Microsoft product.

This disk's documents contain tables that are best viewed when the browser viewing area has been expanded to cover the full width of your monitor's screen.

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