What do AO1 and AO2 indicate in automated weather reporting?

• A. AO1 for stations without a precipitation discriminator; AO2 for stations with a precipitation discriminator
• B. AO1 for manual reports; AO2 for automated reports
• C. AO1 high visibility; AO2 low visibility
• D. AO1 for altitude-only reports; AO2 for temperature reports

Answer: (A)

The main idea here is that AO1 and AO2 describe the capability of automated weather stations to detect precipitation. AO1 means the station does not have a precipitation discriminator, so it relies on a simpler sensor setup and cannot distinguish precipitation from other signals. AO2 means the station does have a precipitation discriminator, allowing it to distinguish precipitation events from non-precipitation signals and report precipitation more accurately. That’s why the correct interpretation is that AO1 is for stations without a precipitation discriminator and AO2 is for stations with one. The other ideas (manual versus automated reporting, visibility, or altitude/temperature focus) don’t relate to what AO1/AO2 specify.