What is the purpose of maintaining weather observations at an ambient monitoring site?

• A. To replace pollutant data.
• B. To calibrate chemical analyzers.
• C. To provide meteorological context for data interpretation and modeling.
• D. To determine the color of the AQI chart.

Answer: (C)

Weather observations provide the meteorological context needed to interpret pollutant measurements and to drive dispersion and exposure modeling. Information like wind speed and direction, temperature, humidity, solar radiation, and atmospheric stability directly affects how pollutants move, react, and deposit in the atmosphere. With this data, analysts can explain when higher concentrations occur (for example, downwind from sources with favorable wind patterns), apply dispersion models, and assess exposure and source attribution. Weather data do not replace pollutant measurements, and calibrations of chemical analyzers rely on calibration gases and standards rather than meteorological data. They also don’t determine the color of the AQI chart, which is driven by pollutant concentrations themselves.