Spatiotemporal Changes of sc-PDSI and Its Dynamic Drivers in Yellow River Basin

Droughts in the Yellow River Basin (YRB), a typical large river in arid to semiarid regions, have been studied extensively. However, the details of the dynamic drivers of meteorological droughts, such as precipitation (P), reference evapotranspiration (ET0), and actual evapotranspiration (AET), are unclear in the YRB, as is whether or not the main dynamic driver of meteorological drought in each subzone is consistent. In order to solve this issue, we analyzed (1) the seasonal distribution of drought in the YRB and (2) sc-PDSI and dynamic driver's trends by using linear trends, Sen's slope, and Z statistics in the YRB from 1951 to 2017; (3) the probability distribution of sc-PDSI, P, ET0, and AET; (4) the correlation of the sc-PDSI with some factors that drive drought; and (5) conducted a Pearson correlation analysis between sc-PDSI and the dynamic drivers at the 0.5 degrees pixel scale. The results show that (1) the northwest region in the YRB was drier than the southeast region, and the drought in spring and winter was more severe than in other seasons. (2) The sc-PDSI showed a downwards trend (-0.47/decade), P and AET also showed a downwards trend (-3.408 mm/decade, -0.27 mm/decade), while ET0 showed a significant upwards trend (12.013 mm/decade) in the YRB. (3) The midstream of the YRB had the highest risk of drought. (4) The P, ET0, and AET were highly correlated with the sc-PDSI on a 12-month timescale. (5) The main dynamic driver of the upstream and downstream drought is P, and the main dynamic driver of the midstream drought was ET0.