What condition is represented by an Alfa index exceeding 400?

An Alfa index exceeding 400 indicates that the data quality is significantly compromised to the point where it is categorized as "unusable." In oceanographic and acoustic assessments, the Alfa index serves as a critical measure of data integrity related to environmental conditions such as noise, temperature, and salinity. When this index is high, it suggests extreme levels of interference or distortion that prevent reliable analysis or operational use of the data collected. Thus, a value greater than 400 makes the data unsuitable for informed decision-making, signaling that caution is needed before proceeding with any conclusions drawn from such data.

This categorization is crucial for operational effectiveness in maritime and oceanographic research, ensuring that only reliable data is utilized for further analysis, modeling, or tactical decisions.