What modifier indicates that a report has been corrected?

The modifier that indicates a report has been corrected is "COR." When a weather report is amended due to inaccuracies or mistakes identified after the initial observation, the "COR" modifier is added to signify that the report is a correction of the previous one. This allows pilots, meteorologists, and other users of weather information to understand that they are receiving an updated and accurate observation.

In contrast, the "RMK" modifier stands for remarks, which provides additional information but does not specifically indicate a correction. "MAN" refers to manually prepared reports, usually denoting that the observation has been generated by a human rather than automatically. The "AUTO" designation is associated with automated reports that are generated by weather stations without human intervention. Therefore, "COR" is the most precise term for signaling that a previous weather report has been corrected.