Data were collected throughout the vertical sampling range of the VLRs, that is at heights between 150 m and 1200 m, and from above the following VLR locations: Malvern, Worcestershire (lat. 52° 06’ 04” N, long. 2° 18’ 38” W) in south-western England from 2000 to 2003; Chilbolton, Hampshire (lat. 51° 8’ 40” N, long. 1° 26’ 13” W) in south-central England from 2004 to 2009; and Rothamsted, Harpenden, Hertfordshire (lat. 51° 48’ 32” N, long. 0° 21’ 27” W) in south-eastern England from 2000 to 2009.