Table 3: Validation of univariate/bivariate model-based droughts against historical severe and extreme drought records in the baseline period (1961–1990).

YearHistorical drought conditionsUnivariate modelUnivariate modelBivariate model
ShaanxiGansu(Severity)(Duration)(Duration-severity)

1962SevereExtreme YYY
1966ModerateSevereYYN
1969MildSevereYYY
1971ModerateExtremeYYY
1972SevereExtremeYYY
1973MildExtremeYYY
1979MildSevereNYN
1980SevereModerateYYY
1981ModerateExtremeYYY
1982ModerateExtremeYYY
1986SevereModerateYYY
1987SevereExtremeYYY

Note: symbol “Y” indicates that the univariate or bivariate drought model is able to effectively identify the historical severe or extreme drought years in Shaanxi or Gansu province; and symbol “N” denotes that the drought model fails to identify the historical drought records in Shaanxi or Gansu.