Influence of Altitude on the Spatiotemporal Variations of Meteorological Droughts in Mountain Regions of the Free State Province, South Africa (1960–2013)
Table 1
Categorization of dryness/wetness.
SPI value occurrence
% occurrence
Nominal SPI class
≥1.645
≤5
Extremely wet
1.282 to 1.644
6–10
Severely wet
0.842 to 1.281
11–20
Moderately wet
0.524 to 0.841
21–33
Slightly wet
−0.523 to 0.523
34–50
Normal
−0.841 to −0.524
21–33
Slight drought
−1.281 to −0.842
11–20
Moderate drought
−1.644 to −1.282
6–10
Severe drought
≤−1.645
≤5
Extreme drought
Adapted from [26] and modified by [27] to enhance suitability for application in southern Africa. The original classification was developed by [28].
