Different changes in dry and humid heat waves over China.

Heat waves (HWs) are expected to increase in many parts of the world under climate warming. However, most existing studies examined the changes in HWs that are derived from air temperature only, possible different changes in humid HWs that consider the combined effects of relative humidity (RH) are much less understood. This study investigates the spatial and temporal changes in two different HW types, namely, dry and humid HWs, in China from 1961 to 2014. Analysis results show that, on average, humid HWs in China occur 20% more frequently than dry HWs. Dry HWs are more commonly located in northern China, while humid events mainly appear in monsoonal southern and eastern regions. It is also found that all measures of both dry and humid HWs across China have been increasing during the past decades, and humid HWs exhibit a more prominent intensifying trend than dry ones. In particular, the national mean frequency, participating days, magnitude, and duration of dry (humid) HWs increased by 0.061 (0.069) events decade−1, 0.32 (0.39) days decade−1, 0.53 (0.62) °C decade−1, and 0.19 (0.21) days decade−1, respectively. These trends vary in different parts of China. The largest increment of dry HW frequency appears in the arid region of northwest China, while the fastest increase of the humid HW frequency is observed in southeastern China. Given the additional stress induced by high humidity to extreme high temperature, we suggest that future climate change mitigation and adaption should consider the change and impacts of humid heat events. [ABSTRACT FROM AUTHOR]