Which service provides weather conditions such as temperature, pressure, and visibility?

The Automated Surface Observing System (ASOS) is the correct answer because it is specifically designed to collect and provide real-time, continuous weather observations at airports and various locations. ASOS systems measure critical weather parameters, including temperature, pressure, and visibility, among other things. This data is essential for aviation operations and plays a vital role in ensuring safety in flight by providing pilots and air traffic controllers with up-to-date information on weather conditions.

The National Weather Service (NWS) is a valuable resource for broader weather forecasts and warnings but does not provide real-time local surface observations as ASOS does. The Federal Aviation Administration (FAA) oversees aviation safety and regulations, but it is not primarily focused on measuring or reporting weather conditions. The Global Positioning System (GPS) is a satellite-based navigation system, which does not measure weather conditions but can provide location and time data. Therefore, ASOS stands out as the dedicated system for the specific observation and reporting of the weather aspects stated in the question.