What type of sensor does an AWS use to measure visibility?

The correct answer pertains to the typical use of an optical sensor in Automatic Weather Stations (AWS) for measuring visibility. An optical sensor operates by analyzing the light that is scattered by particles in the atmosphere, such as dust, rain, or fog. The degree to which light is scattered correlates with how far visibility extends.

In contrast, a laser ceilometer is specifically designed to measure cloud height rather than visibility, although it is related to optical principles. Thermal imagers are used for detecting heat and are not suitable for measuring visibility. Radar sensors are utilized for tracking precipitation and storm systems and may not directly measure visibility but can infer it from weather conditions. Each of these alternatives has its distinct applications but does not fulfill the primary function of measuring visibility in the context of AWS.

The use of optical sensors in AWS is particularly advantageous as they can provide real-time data that is essential for aviation safety and meteorological observations, thereby ensuring accurate assessments of visibility conditions at any given time.