Heat waves, can be exacerbated by the co-occurrence of daytime heat waves and nighttime heat waves. Over China, the Yangtze–Huaihe River basin (YHRB) is the core region of the occurrence of such “compound heat waves”, which exert profound impacts on the society and ecosystems. However, the physical mechanisms responsible for the variability of the YHRB compound heat waves remain unclear. In this study, the interannual variability of YHRB compound heat waves in peak summer (July–August) and its possible causes are investigated based on station observations across China and global reanalysis datasets. A strong link is found between the previous winter Arctic Oscillation (AO) and these peak-summer compound heat waves. During a negative AO in winter, an anomalous tripolar pattern of sea surface temperature (SST) in the North Atlantic is induced by the AO-related atmospheric circulation. Such tripolar SST pattern can persist until the following summer. By that time, oceanic forcing dominates, and positive SST anomalies over the tropical North Atlantic can excite a Rossby wave train propagating eastward from the southwest coast of North America to East Asia. This results in a northwest-southeast tilted high pressure system over the YHRB, favoring the occurrence of peak-summer compound heat waves. Such a delayed influence of the winter AO, together with the North Atlantic capacitor effect, is clearly seen in a case study of the YHBR compound heat waves in 2010. The proposed mechanism is further verified based on numerical experiments with an atmospheric general circulation model.
All Science Journal Classification (ASJC) codes
- Atmospheric Science
- Compound heat waves
- The Arctic Oscillation
- The North Atlantic
- The Yangtze–Huaihe River basin