In the Units column, u indicates units dimensionally equivalent to those for the unmodified standard name.

Table C.1. Standard Name Modifiers

detection_minimumuThe smallest data value which is regarded as a detectable signal.
number_of_observations1The number of discrete observations or measurements from which a data value has been derived.
standard_erroruThe uncertainty of the data value. The standard error includes both systematic and statistical uncertainty. By default it is assumed that the values supplied are for one standard error. If the values supplied are for some multiple of the standard error, the standard_error ancillary variable should have an attribute standard_error_multiplier stating the multiplication factor.
status_flag Flag values indicating the quality or other status of the data values. The variable should have flag_values or flag_masks (or both) and flag_meanings attributes to show how it should be interpreted (Section 3.5, “Flags”).