Visibility

Question 1

What is it?

Answer 1

Greatest distance at which an object can be seen and recognised in daylight
Or at night could be seen and recognised if general illumination were raised to daylight level

Question 2

How are values noted?

Answer 2

Measured using visiometer at automatic sites
Used to be done by observers at manual stations
Except at some Weather Centres and Climate Data Logger stations, where observations are made from non-standard roof top exposure
Measuresd horizontally
Noted I. Decametres (Dm)
Not available - ‘-‘