The aviation meteorology manual of Director General of Civil Aviation comprises a comprehensive set of guidelines relating to weather data for aircraft operations.
These include surface wind direction and speed, visibility, runway visual range, present weather, cloud amount, cloud type (only for cumulonimbus and towering cumulus clouds) and height of cloud base.
For instance, visibility for aeronautical purposes is the greater of a) the greatest distance at which a black object of suitable dimensions, situated near the ground, can be seen and recognised when observed against a bright background; b) the greatest distance at which lights in the vicinity of 1 000 candelas (luminous intensity) can be seen and identified against an unlit background.
The manual also has clear stipulations on landing and takeoff forecasts — a forecast for take-off shall refer to a specified period of time and should contain information on expected conditions over the runway complex with regard to surface wind direction and speed and any variations thereof, temperature, pressure.
A forecast for take-off shall be supplied to operators and flight crew members on request within three hours before the expected time of departure while also subjecting such forecasts to continuous review and, when necessary, amendments.
