Willett et al. (2008)
Also: Willett et al. 2008
Recent changes in surface humidity: Development of the HadCRUH dataset
Willett, K. M., Jones, P. D., Gillett, N. P., & Thorne, P. W. (2008). Recent changes in surface humidity: Development of the HadCRUH dataset. Journal of Climate, 21(20), 5364-5383. Link to PDF
doi: 10.1175/2008JCLI2274.1
References
All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.