Disentangling physical and dynamical drivers of the 2016/17 record-breaking warm winter in China

Abstract

Understanding the physical and dynamical origin of regional climate extremes remains a major challenge in our effort to anticipate the occurrences and mitigate the adverse impacts of these extremes. China was hit by a record-breaking hot winter in 2016/17 with remarkable surface warming over the northern and southeastern regions. Here we made a quantitative attribution of this 2016/17 winter's surface temperature anomalies utilizing an updated version of the coupled atmosphere-surface climate feedback response analysis method (CFRAM), that recently incorporates the effect of aerosols and more species of trace gases (CFRAM-A). The CFRAM-A analysis reveals that the overall warming pattern may be largely attributed to the effects of anomalous water vapor, atmospheric dynamics, and aerosols, followed by anomalies of surface albedo, clouds, solar irradiance, ozone, and carbon dioxide. The effect of methane turns out to be negligible. Anomalies in surface dynamics provides an overall cooling effect, compensating the warming associated with other processes to some extent. Among the three major positive contributors, effects of water vapor and atmospheric dynamics prevail over both northern and southeastern China while the impact of anthropogenic aerosols appears much more pronounced over southeastern China, likely due to the implementation of highly effective emission reduction policies in China since 2013. The CFRAM-A thus provides an efficient, model-free approach for quantitatively understanding sources of regional temperature extremes and for assessing the impacts of environmental policies regulating anthropogenic emissions of aerosols and atmospheric trace gases.