What is a characteristic of Level D ASOS?

A characteristic of Level D Automated Surface Observing System (ASOS) is that it is completely automated without augmentation. This level represents the most advanced form of automatic weather observation systems, where all data is collected and disseminated without the need for human intervention or additional input from observers.

In this fully automated setup, sensors and instruments are designed to operate independently, continuously monitoring weather conditions such as temperature, humidity, wind speed, and precipitation. This level of automation enhances the reliability and frequency of weather reporting, providing real-time data crucial for aviation operations.

The other options include elements associated with various levels of ASOS but do not apply to Level D. For example, augmented systems typically involve human observers, while tower controller reports represent a different operational context. Major airport hubs may utilize various levels of ASOS, but this characteristic is not specific to Level D alone. Thus, the defining trait of Level D ASOS is its complete automation, setting it apart in functionality and operational efficiency.