density function to the given frequency distribution of runoff and soil
moisture series respectively.
Time series of the drought indices were calculated over land grid
cells in China for each model. A drought event was considered as the
period of time when drought index (i.e. SPI, SSWI and SRI) values are
below −1.0, indicating that the deviation from average conditions
exceeds one standard deviation. In order to examine drought characteristics,
three different parameters were used: (1) frequency — the
number of droughts over a defined period; (2) duration — the length
of each drought event; and (3) intensity — the average SPI value for a
drought event. The percentage change in drought index values for the
near future period 2020–2049 with respect to the current period
1971–2000 was used to investigate the changes in drought characteristics.
The near future period 2020–2049was selected because the results
for this period would be most useful for decision makers.