According to the Federal Standard for Siting Meteorological Sensors at Airports (FCM-S4-1994), AMOS sensor groups must be sited for which aspect?

• A. Calibration and standardization
• B. Data transmission
• C. Siting and Exposure
• D. Weather reporting

Answer: (C)

Siting and exposure focus on where the AMOS sensor groups are placed and how they are exposed to the surroundings so the measurements truly reflect the ambient atmosphere. The goal is to minimize biases from nearby obstructions, radiant heat, and wind disturbance that can skew readings. If sensors are too close to buildings, runways, fences, or concrete surfaces, air flow and heating effects can distort wind, temperature, and humidity data. A properly sited sensor group is positioned at the right height, with wind sensors positioned to avoid wake effects, and radiation shields and shade are used to prevent direct sun or heated surfaces from biasing readings. This combination ensures the data represent the free-air conditions rather than local interference, which is essential for accurate weather reporting and aviation operations. Calibration, data transmission, and weather reporting are important in their own right, but the standard emphasizes siting and exposure to guarantee the quality of the observational data.