In addition to the variables that are present in the VDC, VAPOR GUI can calculated and display derived variables using a built-in Python interpreter. Derived variables are calculated on-the-fly in the resolution and LOD that is currently being displayed. The derived variable values are cached so can be reused with little overhead.
VAPOR also supports use of derived variables in IDL, and can display NCL output images in the VAPOR scene. These capabilities are discussed under "Data Analysis with Vapor"
