[1] A Wilhite D. Drought: A Global Assessment, 3(2000).

[2] R Seager, E SmerdonJ, I Cook B et al. Climate Dynamics, 43, 2607(2014).

[3] N Nasrollahi, L Cheng, A Aghakouchak et al. Water Resources Research, 51, 2847(2015).

[4] Ying Xu, Junzhu Ge, Shaoyang Tian et al. Science of The Total Environment, 505, 1043(2015).

[5] R Venteris E, L Downs J, D Tagestad J et al. International Journal of Applied Earth Observation and Geoinformation, 39, 160(2015).

[6] W C Palmer. Department of Commerce, 45, 58(1965).

[7] S Begueria, I Lope-Moreno J, M Vicente-Serrano S. Journal of Geophysical Research: Atmospheres, 116, 1(2011).

[8] S Kimball J, M Zhao, Q Mu et al. Meteorol. Soc, 94, 83(2013).

[9] J Andersen, K Rasmussen, I Sandholt. Remote Sensing of Environment, 79, 213(2002).

[10] Lingtong Du, Naiping Song, Ke Liu et al. Remote Sensing, 9, 177(2017).

[11] L Du, Q Tian, T Yu et al. International Journal of Applied Earth Observation and Geoinformation, 23, 245(2013).

[12] J Hou, L Du, K Liu et al. Theoretical and Applied Climatology, 136, 915(2019).

[14] S Beguería, M Vicente-Serrano S, J López-Moreno. International Journal of Climate, 23, 1696(2010).

[17] M Li, J Yang, C Tan. China Atmosphere, 1399(2015).