极端干旱
中等干旱
轻度干旱
正常
轻度湿润
中等湿润
极端湿润
SPEI
-3
£−2.0
−2.0~−1.0
−1.0~−0.5
−0.5~0.5
0.5~1.0
1.0~2.0
³2.0