It typically defines a physical coordinate corresponding to that dimension. Note that each coordinate variable is a vector and has a shape consisting of just the dimension with the same name. A position along a dimension can be specified using an index . Thus the 700 millibar level would have an index value of 3 in the example above. If a dimension has a corresponding coordinate variable, then this provides an alternative, and often more convenient, means of specifying position along it.
Most attributes provide information about a specific variable.
Some attributes provide information about the dataset as a whole and are called global attributes. Conventional attribute names should be used where applicable. New names should be as meaningful as possible. The external type of an attribute is specified when it is created. The types permitted for attributes are the same as the netCDF external data types for variables.