What is the name of the weather report that provides surface observations at airports?

The METAR report is the correct answer because it is a standard format for reporting weather information, specifically designed to provide routine observations of weather conditions at an airport. These reports include critical data such as temperature, wind speed and direction, visibility, and any significant weather phenomena observed, making them essential for pilots and air traffic controllers.

TAF, which stands for Terminal Aerodrome Forecast, is a forecast rather than an observation, detailing expected weather conditions over a specific period, usually 24 to 30 hours. SIGMETs are used to warn pilots of significant weather events that could impact flying conditions, such as thunderstorms or icing, instead of providing direct surface weather data. PIREPs, or Pilot Reports, are subjective reports from pilots about the current weather conditions based on their in-flight observations, but they do not provide systematic surface observations like the METAR does. Therefore, METAR is specifically designed for surface weather observation at airports, making it the clear choice.