Drought evolution in the Haihe River basin during 1960–2020 and the correlation with global warming, sunspots, and atmospheric circulation indices


 The Haihe River basin is the main grain production base and the highland of economic strategic development in China. Based on daily meteorological data during 1960–2020, the characteristics of drought evolution in the Haihe River basin were analyzed by the standardized precipitation evapotranspiration index (SPEI). Pearson correlation method and cross-wavelet analysis were used to explore the correlation between the SPEI and climate factors (global warming, sunspots, and atmospheric circulation indices). Global warming has led to a trend of increasing drought in the basin, and there is an obvious zonality in the change of the trend, with the strongest impact on the central region of the basin (112°E–120°E, 38°N–41°N). The SPEI was negatively correlated with the number of sunspots. The more sunspots there were, the more severe the drought in the basin. The drought was most susceptible to the El Niño-Southern Oscillation (ENSO) and the Atlantic Multidecadal Oscillation (AMO), followed by the Arctic Oscillation (AO) and the Pacific Decadal Oscillation (PDO). The North Atlantic Oscillation (NAO), the Pacific North America index (PNA), and the Western Pacific index (WP) were the least associated with the drought in the basin.