Risk mapping of heatwave and drought compound event informed by the location of ridge

Abstract:

Compound event, a combination of several spatial-temporal dependent natural hazards, has received increasing attention. The disastrous impact caused by compound events are far beyond the scale of isolated impact induced by single event. Various studies have suggested that the likelihood of future hot and dry compound events are expected to significantly increase across the world, especially in the East Asia. However, apart from statistical frequency analysis and individual event diagnosis, the underlying mechanisms involving multiple drivers, along with the risk mapping for compound events are still rarely explored. Therefore, the present study aims to understand the driving processes of heatwave and drought compound events, in order to provide a future risk mapping in East Asia. We find that as high-pressure ridge system is strongly associated with both heatwave and drought, ridges in the mid-to-high latitudes not only synchronise with co-located drought/heatwave, but also highly correlate with the ones locating in Southeast China. This local response and remote teleconnection provide certain predictability of the occurrence, strength and location, thus risk of heatwave and drought compound event. Moreover, besides ridge system, other possible drivers, such as the absence of atmospheric moisture transport, are also taken into consideration when performing typical event analysis, to deepen understanding of the physical mechanism. Then, a framework including the target events, multiple drivers and their interactions is thus proposed. Lastly, based on the framework, a preliminary risk mapping of future heatwave and drought compound events is conducted in East Asia, mainly informed by the location of ridge.