Editing Cloud base (section)

==Measurement==

The height of the cloud base can be measured using a [[ceilometer]]. This device reflects a beam of light off the cloud base and then calculates its distance using either [[triangulation]] or [[lidar|travel time]].

Alternatively, the cloud base can be estimated from surface measurements of air [[temperature]] and [[humidity]] by calculating the [[lifted condensation level]]. One method for doing this, used by the U.S. [[Federal Aviation Administration]] and often named after Tom Bradbury,<ref>{{cite book|title=Meteorology and Flight|ISBN=0713668318|first=Tom|last=Bradbury|publisher= A&C Black Publishers Ltd}}</ref> is as follows:

#Find the difference between the surface temperature and the [[dew point]]. This value is known as the "spread".
#Divide the spread by 4.4 (if temperatures are in °F) or 2.5 (if temperatures are in °C), then multiply by 1000. This will give the altitude of the cloud base in feet above ground level. Put in a simpler way, 400 feet for every 1°C dew point spread. For metric divide the spread in °C by 8 and multiply by 1000 and get the cloud base in meters.
#Add the results from step (2) to the field elevation to obtain the altitude of the cloud base above mean sea level.