“…SPEI estimation requires monthly water deficit (MWD), that is, the difference of monthly precipitation (P) and monthly potential evapotranspiration (PET). Hargreaves (Rhee et al, 2016;Dibike et al, 2017;Oguntunde et al, 2017;Spinoni et al, 2018), Thornthwaite (Törnros and Menzel, 2014;Smirnov et al, 2016;Wu et al, 2016;Bonsal et al, 2017;Chen and Sun, 2017;Feng et al, 2017;Khan et al, 2017), and Penman-Monteith (Wang et al, 2014;Feng et al, 2017;Gao et al, 2017;Huang et al, 2018;Zhang et al, 2018) are the three most commonly used PET estimation methods employed in SPEI based drought studies under projected scenarios. Penman-Monteith method is the best reported method and data intensive, Hargreaves method utilizes daily maximum and minimum temperature whereas Thonthwaite requires monthly mean temperature.…”