The super-heat wave in eastern China during July-August 2013: a perspective of climate change.

ABSTRACT Eastern China suffered a record-breaking heat wave throughout almost all of summer, during 2013. Recent studies found a discernible impact of anthropogenic forcing on this extreme heat wave event. In this study, we investigate the role of multidecadal variability ( MDV) in regulating the likelihood of the 2013 heat wave event. Using the ensemble empirical mode decomposition ( EEMD) method, we decomposed the heat wave index series into three components: (1) a non-linear secular trend ( ST), representing the long-term anthropogenic warming; (2) MDV; and (3) the residual high-frequency variability. For the period 1873-2013, the linear trend of heat wave strength ( HW-S, defined as the July-August mean temperatures) was 0.06 °C per decade, mainly because of the contribution of ST. MDV plays an important role in regulating changes over decades. ST and MDV together form a changing climate background ( CB) for extreme events. The 2013 heat wave event would be almost impossible under the pre-industrial CB but becomes likely under the long-term warming background, with a return period of longer than 103 years. When the positive phase of MDV is added to the secular warming background (the current CB), the return period of a super-heat wave such as the 2013 event becomes about 42 (12-103) years. The Atlantic Multidecadal Oscillation ( AMO) shows significant correlation with the MDV component of the HW-S in Shanghai. The correlation pattern between the AMO and MDV of July-August temperatures over the Northern Hemisphere is analysed to explain the AMO-Shanghai relationship. It is suggested that the likelihood of such an extreme event will increase with further long-term climate warming, modified by low-frequency oceanic variations such as the AMO. [ABSTRACT FROM AUTHOR]