Abstract: Using precipitation and temperature observations from national meteorological stations in China during 1961-2017, the weekly standardized Palmer drought severity index was proposed, and heat waves were recognized by using the relative high temperature threshold method. On this basis, the spatiotemporal evolution features of droughts and heat waves, as well as their concurrences were analyzed. Results reveal that: 1) droughts and heat waves occurred frequently in summer. The annual series of the percentage of meteorological stations under droughts and heat waves both indicated a downward tendency before 1995, and an upward tendency afterwards. 2) Heat waves took place much more frequently at most stations, and so did drought events in northeast and north China and east Yunnan Province. The freqency of heat waves changed abruptly in the 1980s and 1990s. Such changes presented a similar spatial pattern with droughts. 3) Yunnan suffered the most concurrent droughts and heat waves, followed by the northeastern region, the northern region, and coastal areas of Guangxi and Guangdong. In contrast, the Changjiang River basin and northern parts of Xinjiang experienced least concurrent events. 4) Among concurrent events, approximately 65% of heat waves occurred in the onset-development stage of droughts, whereas for Yunnan and southern parts of the Changjiang River basin, heat waves mostly occurred in the recovery stage of droughts. 5) Except for the Huaihe River basin and the middle and lower reaches of the Changjiang River, concurrent droughts and heat waves significantly increased for the majority of China.

Key words: drought, heat wave, spatial and temporal distribution, evolution characteristics, concurrence