Contrail Classifications
Persistent and Dispersed. p+d.
Figure 1 is a good example of the extent to which contrails can cover the sky when they are both persistent and dispersed. At the top of the photo a contrail can be seen to have spread out and is now covering a large portion of the sky. It is these types of contrails that will be of the most climatic significance.
Figure 1. Persistent and Dispersed Contrails.
Leigh, P. 15/8/2003. Lancaster University.
Persistent and Non Dispersed. p+nd
Figure 2 shows a persistent and dispersed contrail with a persistent and non dispersed contrail in the foreground going form the top to the bottom of the picture.
Figure 2. Persistent and Non-Dispersed Contrails.
Leigh, P. 19/12/2002. Lancaster University.
Non Persistent and Dispersed. np+d
These types of contrails are the least common form as if a contrail is non persistent (persists for less than 5 minutes) then it is quite unlikely to disperse to any extent within this short time. Consequently a photographic example of such a contrail is currently unavailable.
Non Persistent and Non Dispersed. np+nd
Figure 3 shows an example of a non persistent and non dispersed contrail. It can be seen that the contrail is remaining in its linear form but is already beginning to break up (behind the cloud that is in the foreground) and so is unlikely to persist for longer than 5 minutes, after which time a contrail is generally classed as persistent.
Figure 3. Non-Persistent and Non-Dispersed Contrails.
Leigh, P. 10/9/2001. Lancaster University