To describe fog as partial, what descriptor code will be used in METAR?

The correct descriptor code for partial fog in METAR is "MIFG." This code signifies "shallow fog" and is specifically used to indicate fog that does not cover the entire area, thus qualifying it as partial rather than complete fog. The use of "MIFG" helps meteorologists and pilots distinguish between different intensities of fog, which is crucial for flight operations and safety.

The other options represent different weather phenomena or descriptors that do not refer specifically to partial fog. "FG" generally indicates fog in a more general sense without specifying its intensity. "BR" is used for mist, which is a different meteorological phenomenon characterized by visibility reduction but not by the same moisture content or visibility restrictions that fog presents. "PR" is short for "partial," but it is not a standard descriptor used to describe fog in METAR reports.

Having the correct terminology helps ensure that weather reports are clear and useful for aviation operations.