ATPL: Select the acronym corresponding to the following definition: an special NOTAM series notifying, by means of a specific format, an important change for the aircraft operations, due to a volcano activity, a volcano eruption or a volcanic ash cloud.

Explanation: Select the acronym corresponding to the following definition: an special NOTAM series notifying, by means of a specific format, an important change for the aircraft operations, due to a volcano activity, a volcano eruption or a volcanic ash cloud.