SEACOOS CDL v2.0 December 9, 2004 19 :short_name Text. Descriptive acronym or short version of a longer name that indicates the variable’ s content.  This does not have to match the variable name used by the netCDF file. No spaces or tabs are allowed in the value string. Example: “sst” or “wtemp” :_FillValue Scalar value, same data type as the variable. This value denotes valid data that is not present or outside the valid range for the variable or pre- fill. Note the underscore character and capitalization.  If the _FillValue attribute is presented with the global attributes then each variable inherits this value unless specified as different with a variable attribute. Example: -9999; :missing_value Scalar value, same data type as the variable. This attribute is not treated in any special way by the netCDF library, but is often useful documentation and may be used by specific applications or for second fill value. Example: -9999; :valid_range Scalar values, same data type as the variable. Values that describe the geophysical range of the variable. Example: 0.,360; :reference Text. Description of the reference datum for the variable.   Example: “clockwise from true North” or “Mean Low-low Water (MLLW)” :positive Value. Description of direction of positive if it cannot be inferred from the units.  Most often used for height or depth variables. Example: “up” or “down” :axis Text. Indicates which axis if the variable is an independent variable. Example: “X” or “Y” or “Z” or “T” :z Value. Depth or height of fixed instrument if dimension of the z-variable is more than one. If the dimension of the z-variable is only one, then that value is taken as the depth or height of the data variable. Example: 10. :sample_interval Value. How often the data is sampled in units chosen for the time variable. For exa mple, the instrument samples every 6 minutes or 360 seconds. Example: 360. :average_interval Value. Period over which data are averaged.  For example, wind data are sampled every 6 minutes, but data are collected and averaged over 2 minutes or 120 seconds.   Example: 120.