Temporal and spatial variability of drought in Huang-Huai-Hai River Basin, China

Drought is a kind of extreme hydrological event. With the penetration of climate change impact, severity, areal extent, and frequency of drought are increasing, especially in Huang-Huai-Hai River Basin, which plays a key role in China's agriculture production. Analyzing the regional temporal and spatial variability in the context of climate change could provide a basis for the evasion of disasters and risk. The maximum number of consecutive dry days was selected as the indicator to analyze the decadal variability of drought severity, areal extent, and spatial variability of drought frequency in different seasons in Huang-Huai-Hai River Basin. Based on these, temporal and spatial variability of two kinds of special extreme events-consecutive drought and heavy rain after drought-were studied. The results showed that: (1) Huang-Huai-Hai River Basin mainly experienced moderate drought and severe drought. Moderate drought mainly occurs in autumn. High-frequency region of moderate drought is located in the plain of Huang-Huai-Hai River Basin, and its area is approximately 22.7 % of Huang-Huai-Hai River Basin. Severe drought often occurs in spring with high-frequency region in the upstream of the Yellow River. The area of this high-frequency region is about 6 % of Huang-Huai-Hai River Basin. (2) During 1961 similar to 2011, the areal extent of summer severe drought, autumn severe drought, and extreme drought all showed increasing trend, in which the increasing trend of the autumn severe drought area in the Yellow River has reached the significance level alpha = 0.05. (3) Consecutive drought of several seasons often took place in Ningxia plain and Hetao plain which lie in the northwest of the Yellow River Basin. In the recent 20 years, consecutive drought from spring to summer and consecutive drought from summer to autumn occurred frequently. Drought-flood abrupt alternation such as heavy rain after drought often occurred in summer temporally and Huaihe River Basin spatially.