The data in this branch of the 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. To conserve space, all the stranger files here have been gzipped.
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. Our implementation of netCDF differs from some others in that it does not contain explicit series of a time variable. We have placed a start time and an ending time among the global variables, which is sufficient for data with a fixed time increment. 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. For example, an experiment in which 30 instruments produced data 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
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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. Unidata's 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 Unidata for the UNIX and Windows environments provide complete access to and control of the netCDF format.
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