What do transmissometers measure?

Transmissometers are specialized instruments used primarily in aviation and meteorology to measure the extinction coefficient of the atmosphere. This coefficient quantifies the amount of light attenuated by particles and gases in the air over a specified distance. In practical terms, transmissometers provide crucial information regarding visibility conditions, which is particularly important for flight operations and runway safety.

By measuring the extinction coefficient, transmissometers help determine how far light can travel through the atmosphere under prevailing conditions, thereby indicating visibility levels. This information is vital for pilots and air traffic controllers to make safe operational decisions, especially in low visibility scenarios.

Other options, while related to airside operations and weather, do not reflect the primary purpose of transmissometers. Runway conditions pertain to the state of the runway surface, weather patterns involve broader climatic conditions over time, and wind speed measurements relate to atmospheric conditions but are not directly linked to the function of a transmissometer. Thus, the correct answer underscores the specific role of transmissometers in measuring atmospheric transparency through the extinction coefficient.