4Ponce V M, Pandey R P, Ercan S. Characterization of drought across climatic spectrum [ J ]. Journal of Hydro- logic Engineering,2000,5 (2) : 222-224.
5Liu Xiaomang,Zhang Dan, Luo Yuzhou,et al. Spatial and temporal changes in aridity index in northwest China: 1960 to 2010 [J]. Theoretical and Applied Climatology, 2013,112(1/2) :307-316.
6Solomon S, Qin D, Manning M, et al. Climate change 2007 : The physical science basis [ M ] f/Contribution of Working GroupI to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge, UK and New York, USA: Cambridge University Press, 2007:3-4.
7Chattopadhyay N,Hulme M. Evaporation and potential e- vapotranspiration in India under conditions of recent and future climate change[ J]. Agricultural and Forest Mete- orology, 1997,87 ( 1 ) : 55-73.
8Thomas A. Spatial and temporal characteristics of poten- tial evapotranspiration trends over China [ J ]. Interna- tional Journal of Climatology,2000,20(4) : 381-396.
9Abtew W,Oheysekera J,Iricanin N. Pan evaporation and potential evapotranspiration trends in South Florida [ J]. Hydrol Process,2011,25 (6) :958-969.
10Brutsaert W,Parlange M. Hydrologic cycle explains the e- vaporation paradox[ J]. Nature, 1998,396(6706) : 30.
