SVP depends on temperature. As
temperature increases, more molecules
are energetic enough to escape into the air.
Concept applies to an ice
surface. SVP over ice is lower because water molecules are bonded more tightly to
ice.
For the temperatures of
interest, some water molecules are energetic
enough to escape into atmosphere and SVP>0.
Williams p62
dry E>C
saturatedE=C
warmedE>C
cooled E<C