Differences in severe storms in cold versus warm climate regimes: what do 500+ years of historical data tell us?

Recent climate studies often predict the occurrence of extreme weather or climate conditions under certain global warming scenarios using climate models. However, it is usually unclear about the nature of such extreme weather and how such weather extremities occur as the resolution of the current generation climate models is usually not high enough to resolve individual storm systems let alone pinning down their 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 In this study, we utilize the meteorological series derived from the REACHES climate database compiled from Chinese historical documents (Wang et al., 2018, Sci. Data 8:180288) as well modern weather data to pin down the type of storms and to study the respective physical mechanisms responsible for the extreme events that preferably occur in cold versus warm climate regime. We construct convection index series based on hailfall and lightning records in China in REACHES database for the period of 1368-1911 and compare them with the reconstructed temperature series from the same database for the same period (Wang et al., 2024, Sci. Data, 11, 1117). The comparison will reveal that severer convective storms tend to occur more frequently in cold climate regime than warm climate regime. On the other hand, modern observational data demonstrate that the high LWC (but not necessarily severe) storms are the type most likely to lead to extreme events in the present warming climate.Finally, storm thermodynamics and dynamics will be used to explain why such differences occur in different climate regimes.