Assessment of Regional Drought Trend and Risk over China: A Drought Climate Division Perspective

Abstract A combination of Ward’s and k-means clustering was applied to a 3-month standardized precipitation index (SPI-03), and eight divisions of homogeneous drought variation throughout China were identified from the perspective of meteorological and agricultural droughts. A greater meridional gradient appeared over eastern China (six divisions) than over western China (two divisions). The climate division facilitated the evaluating of not only regional but also widespread droughts. Trend evaluation showed that western north China (WNC) has become increasingly wet in recent decades, while northern northeast China (NNE) has become increasingly dry. The Yangtze River valley (YZ) tended to experience less and weaker drought after the late 1970s. Southern northeast China (SNE) and the southwestern China–Tibetan Plateau (SW-TP) showed a decreasing trend in long-term but not short-term SPIs, implying that long-term drought conditions might develop continuously, thus allowing the following droughts to develop more rapidly and with a stronger intensity. Examination of the drought risk under El Niño revealed that northern regions were likely to suffer from drought rather than flood in the developing phase and the reverse in the decaying phase. Southeastern China (SE) and the YZ were vulnerable to flood rather than drought in the mature and decaying spring, with SE subjected to drought in the decaying summer. Such a distinctive regional pattern of drought risks was closely connected with the abnormal moisture supply patterns modulated by ENSO in different phases.