photo #5283999

On a wet autumn day, Knox Cummin (Cloud Appreciation Society Member 49,212) spotted ragged fragments of cloud rising from the tree canopy to merge with Stratocumulus clouds near Huntington, Vermont, US. Cloud shreds emerging from the trees like this are classified as Stratus fractus silvagenitus – the third part referring to the role trees play in forming the clouds (silva being Latin for ‘forest’). Trees, with their often-textured bark and convoluted structures of branches, twigs and leaves, have huge surface areas that can lead to rapid evaporation when wet after rain. Combined with moisture released into the air through the pores of leaves, in a process known as transpiration, this means that a woodland canopy can contribute greatly to the air’s humidity. If the humid air rises, it cools and its water vapour can condense into droplets and appear like Knox’s rags of tree-made clouds.