Extreme weather types and their physical mechanisms in cold versus warm climate regimes: evidence from historical and modern climate data

Possibility of the occurrence of extreme weather and climate is often predicted in recent climate impact studies under certain global warming scenarios using climate models. However, it is usually unclear how such weather extremities occur as the resolution of the current generation climate models is not good enough to resolve individual storm system let alone pinning down the physical mechanisms. This ambiguity in physical mechanism impedes the better understanding of the nature of these extreme weather/climate events and can lead to ineffective mitigation and/or adaptation measures. For example, when the term extreme rainfall is mentioned, it is unclear whether it is caused by severe convective storms or by regular storms that have higher liquid water contents (LWC), as both can lead to large amount of rainfall. But the detailed physical mechanisms of these two types of storms are different. Clearly it is desirable to remove such ambiguity and clarify what type of storms would occur in certain climate regime.

 In this study, we utilize the meteorological series derived from the REACHES climate database compiled from Chinese historical documents (Wang et al., 2018; 2024) as well modern weather data to pin down the type of storms and the respective physical mechanisms responsible for the extreme events that preferably occur in cold versus warm climate regime. We use the REACHES reconstructed temperature series in China in 1368-1911 and construct convection index series to show that the severe deep convective storms are the preferable type that causes extreme weather events in cold climate regime and utilize modern observational data to demonstrate that the high LWC (but not necessarily severe) storms are the type most likely to lead to extreme events.

Finally, physics-based storm model simulation results will be used to illustrate the dynamical processes of these two types of storms and explain why they lead to different precipitation patterns.