Fig. 2: The Standardize Precipitaion Index.

The Standardized Precipitation Index series with a decadal filter from 1989 to 2015, calculated with land-only precipitation from the GPCP dataset74. Orange for negative and green for positive precipitation anomalies. NEB region on the top and WAF region on the bottom. The dashed line indicates the +1 and −1 SPI limits for wet and dry conditions. The correlation between the two curves is −0.82 (p < 0.05) from 1980 to 2005.