Final answer:
RVR stands for Runway Visual Range and is a critical component of a METAR report for indicating the horizontal visibility down an airport's runway, which is crucial for pilots during takeoff and landing in poor visibility conditions.
Step-by-step explanation:
RVR, or Runway Visual Range, is a term used in aviation to describe the horizontal distance a pilot can see down the runway in the direction of landing or takeoff. It is a critical component of a METAR report, which is a standardized format for reporting weather conditions at an airport. METARs are essential for pilots and air traffic control to ensure safety during flight operations, especially under Instrument Flight Rules (IFR).
The RVR is measured using transmissometers installed along the runway, which calculate the distance over which the intensity of light is reduced to a specified level. This measurement is most relevant in poor visibility conditions, such as fog, heavy rain or snow, which can significantly reduce a pilot's visibility. When the RVR is reported on a METAR, it aids pilots in making decisions about whether it is safe to takeoff or land, and what type of instrument approach procedure they may need to use.