The scientific basis for the humidity downscaling is outlined in the following publication:
Pierce, D. W. and D. R. Cayan, 2015: Downscaling humidity with Localized Constructed Analogs (LOCA) over the conterminous United States. Climate Dynamics, DOI 10.1007/s00382-015-2845-1. Author’s copy of the paper.
Information on the humidity downscaling process is available for: